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Insulinomas

An insulinoma Insulinoma A benign tumor of the pancreatic beta cells. Insulinoma secretes excess insulin resulting in hypoglycemia. Pancreatic Neuroendocrine Tumors (PanNETs) is a type of functional neuroendocrine tumor Tumor Inflammation that manifests with hypoglycemia Hypoglycemia Hypoglycemia is an emergency condition defined as a serum glucose level ≤ 70 mg/dL (≤ 3.9 mmol/L) in diabetic patients. In nondiabetic patients, there is no specific or defined limit for normal serum glucose levels, and hypoglycemia is defined mainly by its clinical features. Hypoglycemia due to autologous secretion Secretion Coagulation Studies of insulin Insulin Insulin is a peptide hormone that is produced by the beta cells of the pancreas. Insulin plays a role in metabolic functions such as glucose uptake, glycolysis, glycogenesis, lipogenesis, and protein synthesis. Exogenous insulin may be needed for individuals with diabetes mellitus, in whom there is a deficiency in endogenous insulin or increased insulin resistance. Insulin. It more commonly presents as a solitary benign Benign Fibroadenoma tumor Tumor Inflammation but can sometimes be associated with MEN type 1 Type 1 Spinal Muscular Atrophy ( MEN1 MEN1 A form of multiple endocrine neoplasia that is characterized by the combined occurrence of tumors in the parathyroid glands, the pituitary gland, and the pancreatic islets. The resulting clinical signs include hyperparathyroidism; hypercalcemia; hyperprolactinemia; cushing disease; gastrinoma; and zollinger-ellison syndrome. This disease is due to loss-of-function of the men1 gene, a tumor suppressor gene on chromosome 11 (locus: 11q13). Multiple Endocrine Neoplasia). Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship present with fasting hypoglycemia Hypoglycemia Hypoglycemia is an emergency condition defined as a serum glucose level ≤ 70 mg/dL (≤ 3.9 mmol/L) in diabetic patients. In nondiabetic patients, there is no specific or defined limit for normal serum glucose levels, and hypoglycemia is defined mainly by its clinical features. Hypoglycemia, which may manifest as episodes of diaphoresis, palpitations Palpitations Ebstein’s Anomaly, tremor Tremor Cyclical movement of a body part that can represent either a physiologic process or a manifestation of disease. Intention or action tremor, a common manifestation of cerebellar diseases, is aggravated by movement. In contrast, resting tremor is maximal when there is no attempt at voluntary movement, and occurs as a relatively frequent manifestation of parkinson disease. Myotonic Dystrophies, and confusion. Insulinoma Insulinoma A benign tumor of the pancreatic beta cells. Insulinoma secretes excess insulin resulting in hypoglycemia. Pancreatic Neuroendocrine Tumors (PanNETs) is usually diagnosed with high insulin Insulin Insulin is a peptide hormone that is produced by the beta cells of the pancreas. Insulin plays a role in metabolic functions such as glucose uptake, glycolysis, glycogenesis, lipogenesis, and protein synthesis. Exogenous insulin may be needed for individuals with diabetes mellitus, in whom there is a deficiency in endogenous insulin or increased insulin resistance. Insulin, C peptide, and proinsulin levels despite the patient’s hypoglycemia Hypoglycemia Hypoglycemia is an emergency condition defined as a serum glucose level ≤ 70 mg/dL (≤ 3.9 mmol/L) in diabetic patients. In nondiabetic patients, there is no specific or defined limit for normal serum glucose levels, and hypoglycemia is defined mainly by its clinical features. Hypoglycemia. Localization of the insulinoma Insulinoma A benign tumor of the pancreatic beta cells. Insulinoma secretes excess insulin resulting in hypoglycemia. Pancreatic Neuroendocrine Tumors (PanNETs) is done with imaging. Surgical removal of the insulinoma Insulinoma A benign tumor of the pancreatic beta cells. Insulinoma secretes excess insulin resulting in hypoglycemia. Pancreatic Neuroendocrine Tumors (PanNETs) is the treatment of choice, but medical therapy may be utilized to prevent hypoglycemia Hypoglycemia Hypoglycemia is an emergency condition defined as a serum glucose level ≤ 70 mg/dL (≤ 3.9 mmol/L) in diabetic patients. In nondiabetic patients, there is no specific or defined limit for normal serum glucose levels, and hypoglycemia is defined mainly by its clinical features. Hypoglycemia in those who cannot undergo surgery.

Last updated: Sep 1, 2022

Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

Definition and Epidemiology

Definition

Insulinomas are pancreatic neuroendocrine tumors Pancreatic Neuroendocrine Tumors Pancreatic neuroendocrine tumors (PanNETs) arise from the endocrine pancreas (islet cells) and represent 2%-5% of primary pancreatic neoplasms; the other 95%-98% of pancreatic neoplasms are from the exocrine pancreas. The majority of PanNETs are nonfunctional (50%-75%), while others that are functional may be benign or malignant. Pancreatic Neuroendocrine Tumors (PanNETs) that are derived from beta cells and secrete insulin Insulin Insulin is a peptide hormone that is produced by the beta cells of the pancreas. Insulin plays a role in metabolic functions such as glucose uptake, glycolysis, glycogenesis, lipogenesis, and protein synthesis. Exogenous insulin may be needed for individuals with diabetes mellitus, in whom there is a deficiency in endogenous insulin or increased insulin resistance. Insulin.

Epidemiology

  • Incidence Incidence The number of new cases of a given disease during a given period in a specified population. It also is used for the rate at which new events occur in a defined population. It is differentiated from prevalence, which refers to all cases in the population at a given time. Measures of Disease Frequency: approximately 1–4 cases per million people per year
  • No sex Sex The totality of characteristics of reproductive structure, functions, phenotype, and genotype, differentiating the male from the female organism. Gender Dysphoria or ethnic predisposition
  • All age groups
  • In 5%–10% of cases, insulinomas are malignant.
  • 6% of cases associated with MEN type 1 Type 1 Spinal Muscular Atrophy ( MEN1 MEN1 A form of multiple endocrine neoplasia that is characterized by the combined occurrence of tumors in the parathyroid glands, the pituitary gland, and the pancreatic islets. The resulting clinical signs include hyperparathyroidism; hypercalcemia; hyperprolactinemia; cushing disease; gastrinoma; and zollinger-ellison syndrome. This disease is due to loss-of-function of the men1 gene, a tumor suppressor gene on chromosome 11 (locus: 11q13). Multiple Endocrine Neoplasia) syndrome (associated with parathyroid Parathyroid The parathyroid glands are 2 pairs of small endocrine glands found in close proximity to the thyroid gland. The superior parathyroid glands are lodged within the parenchyma of the upper poles of the right and left thyroid lobes; the inferior parathyroid glands are close to the inferior tips or poles of the lobes. Parathyroid Glands: Anatomy, pituitary Pituitary A small, unpaired gland situated in the sella turcica. It is connected to the hypothalamus by a short stalk which is called the infundibulum. Hormones: Overview and Types, and pancreatic tumors)

Related videos

Pathophysiology

Normal insulin Insulin Insulin is a peptide hormone that is produced by the beta cells of the pancreas. Insulin plays a role in metabolic functions such as glucose uptake, glycolysis, glycogenesis, lipogenesis, and protein synthesis. Exogenous insulin may be needed for individuals with diabetes mellitus, in whom there is a deficiency in endogenous insulin or increased insulin resistance. Insulin physiology

Synthesis Synthesis Polymerase Chain Reaction (PCR):

  • Proinsulin:
    • Stored in secretory granules
    • Composed of three peptide chains: A, B, and C
    • Cleaved in the Golgi apparatus → insulin Insulin Insulin is a peptide hormone that is produced by the beta cells of the pancreas. Insulin plays a role in metabolic functions such as glucose uptake, glycolysis, glycogenesis, lipogenesis, and protein synthesis. Exogenous insulin may be needed for individuals with diabetes mellitus, in whom there is a deficiency in endogenous insulin or increased insulin resistance. Insulin and C peptide
  • Insulin Insulin Insulin is a peptide hormone that is produced by the beta cells of the pancreas. Insulin plays a role in metabolic functions such as glucose uptake, glycolysis, glycogenesis, lipogenesis, and protein synthesis. Exogenous insulin may be needed for individuals with diabetes mellitus, in whom there is a deficiency in endogenous insulin or increased insulin resistance. Insulin
    • Consists of 2 chains connected by 2 disulfide linkages: A and B chains
    • Released from pancreatic beta cells

Regulation:

  • Stimulated by:
    • Meal constituents:
      • Glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance
      • Amino acids Acids Chemical compounds which yield hydrogen ions or protons when dissolved in water, whose hydrogen can be replaced by metals or basic radicals, or which react with bases to form salts and water (neutralization). An extension of the term includes substances dissolved in media other than water. Acid-Base Balance
      • Free fatty acids Acids Chemical compounds which yield hydrogen ions or protons when dissolved in water, whose hydrogen can be replaced by metals or basic radicals, or which react with bases to form salts and water (neutralization). An extension of the term includes substances dissolved in media other than water. Acid-Base Balance
    • Enteric hormones Hormones Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. Hormones: Overview and Types:
      • Glucagon-like peptide 1 (GLP-1)
      • Gastric inhibitory polypeptide Gastric inhibitory polypeptide A gastrointestinal peptide hormone of about 43-amino acids. It is found to be a potent stimulator of insulin secretion and a relatively poor inhibitor of gastric acid secretion. Gastrointestinal Neural and Hormonal Signaling ( GIP GIP A gastrointestinal peptide hormone of about 43-amino acids. It is found to be a potent stimulator of insulin secretion and a relatively poor inhibitor of gatsric acid secretion. Gastrointestinal Neural and Hormonal Signaling, also known as glucose-dependent insulinotropic polypeptide)
      • Cholecystokinin Cholecystokinin A peptide, of about 33 amino acids, secreted by the upper intestinal mucosa and also found in the central nervous system. It causes gallbladder contraction, release of pancreatic exocrine (or digestive) enzymes, and affects other gastrointestinal functions. Cholecystokinin may be the mediator of satiety. Gastrointestinal Secretions
    • Neural agonists:
      • Beta-adrenergic receptor Receptor Receptors are proteins located either on the surface of or within a cell that can bind to signaling molecules known as ligands (e.g., hormones) and cause some type of response within the cell. Receptors stimulation via norepinephrine Norepinephrine Precursor of epinephrine that is secreted by the adrenal medulla and is a widespread central and autonomic neurotransmitter. Norepinephrine is the principal transmitter of most postganglionic sympathetic fibers, and of the diffuse projection system in the brain that arises from the locus ceruleus. Receptors and Neurotransmitters of the CNS
      • Acetylcholine Acetylcholine A neurotransmitter found at neuromuscular junctions, autonomic ganglia, parasympathetic effector junctions, a subset of sympathetic effector junctions, and at many sites in the central nervous system. Receptors and Neurotransmitters of the CNS 
      • Vasoactive intestinal polypeptide Vasoactive intestinal polypeptide A highly basic, 28 amino acid neuropeptide released from intestinal mucosa. It has a wide range of biological actions affecting the cardiovascular, gastrointestinal, and respiratory systems and is neuroprotective. It binds special receptors (receptors, vasoactive intestinal peptide). VIPoma ( VIP VIP A highly basic, 28 amino acid neuropeptide released from intestinal mucosa. It has a wide range of biological actions affecting the cardiovascular, gastrointestinal, and respiratory systems and is neuroprotective. It binds special receptors. Gastrointestinal Neural and Hormonal Signaling)
  • Inhibited by:
    • Alpha-adrenergic receptor Receptor Receptors are proteins located either on the surface of or within a cell that can bind to signaling molecules known as ligands (e.g., hormones) and cause some type of response within the cell. Receptors stimulation via norepinephrine Norepinephrine Precursor of epinephrine that is secreted by the adrenal medulla and is a widespread central and autonomic neurotransmitter. Norepinephrine is the principal transmitter of most postganglionic sympathetic fibers, and of the diffuse projection system in the brain that arises from the locus ceruleus. Receptors and Neurotransmitters of the CNS
    • Somatostatin Somatostatin A 14-amino acid peptide named for its ability to inhibit pituitary growth hormone release, also called somatotropin release-inhibiting factor. It is expressed in the central and peripheral nervous systems, the gut, and other organs. SRIF can also inhibit the release of thyroid-stimulating hormone; prolactin; insulin; and glucagon besides acting as a neurotransmitter and neuromodulator. In a number of species including humans, there is an additional form of somatostatin, srif-28 with a 14-amino acid extension at the n-terminal. Gastrointestinal Secretions 

Release Release Release of a virus from the host cell following virus assembly and maturation. Egress can occur by host cell lysis, exocytosis, or budding through the plasma membrane. Virology:

  1. Glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance enters beta cells.
  2. ATP production from glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance metabolism
  3. Closure of ATP-sensitive K-channels
  4. Beta cell depolarization Depolarization Membrane Potential
  5. Calcium Calcium A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes. Electrolytes ( Ca CA Condylomata acuminata are a clinical manifestation of genital HPV infection. Condylomata acuminata are described as raised, pearly, flesh-colored, papular, cauliflower-like lesions seen in the anogenital region that may cause itching, pain, or bleeding. Condylomata Acuminata (Genital Warts)) influx due to voltage-gated Ca-channel opening 
  6. Insulin Insulin Insulin is a peptide hormone that is produced by the beta cells of the pancreas. Insulin plays a role in metabolic functions such as glucose uptake, glycolysis, glycogenesis, lipogenesis, and protein synthesis. Exogenous insulin may be needed for individuals with diabetes mellitus, in whom there is a deficiency in endogenous insulin or increased insulin resistance. Insulin and C-peptide C-peptide The middle segment of proinsulin that is between the n-terminal b-chain and the c-terminal a-chain. It is a pancreatic peptide of about 31 residues, depending on the species. Upon proteolytic cleavage of proinsulin, equimolar insulin and c-peptide are released. C-peptide immunoassay has been used to assess pancreatic beta cell function in diabetic patients with circulating insulin antibodies or exogenous insulin. Half-life of c-peptide is 30 min, almost 8 times that of insulin. Diabetes Mellitus exocytosis Exocytosis Cellular release of material within membrane-limited vesicles by fusion of the vesicles with the cell membrane. The Cell: Cell Membrane

Function:

  • Glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance uptake in skeletal muscle and adipose tissue Adipose tissue Adipose tissue is a specialized type of connective tissue that has both structural and highly complex metabolic functions, including energy storage, glucose homeostasis, and a multitude of endocrine capabilities. There are three types of adipose tissue, white adipose tissue, brown adipose tissue, and beige or “brite” adipose tissue, which is a transitional form. Adipose Tissue: Histology via glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance transporter type 4 Type 4 Spinal Muscular Atrophy (GLUT4, an insulin-dependent transporter)
  • ↑ Glycogen synthesis Synthesis Polymerase Chain Reaction (PCR)
  • ↑ Protein synthesis Synthesis Polymerase Chain Reaction (PCR) and ↓ proteolysis
  • ↑ Triglyceride synthesis Synthesis Polymerase Chain Reaction (PCR) and ↓ lipolysis Lipolysis The metabolic process of breaking down lipids to release free fatty acids, the major oxidative fuel for the body. Lipolysis may involve dietary lipids in the digestive tract, circulating lipids in the blood, and stored lipids in the adipose tissue or the liver. A number of enzymes are involved in such lipid hydrolysis, such as lipase and lipoprotein lipase from various tissues. Nonalcoholic Fatty Liver Disease
  • Gluconeogenesis Gluconeogenesis Gluconeogenesis is the process of making glucose from noncarbohydrate precursors. This metabolic pathway is more than just a reversal of glycolysis. Gluconeogenesis provides the body with glucose not obtained from food, such as during a fasting period. The production of glucose is critical for organs and cells that cannot use fat for fuel. Gluconeogenesis and glycogenolysis Glycogenolysis The release of glucose from glycogen by glycogen phosphorylase (phosphorolysis). The released glucose-1-phosphate is then converted to glucose-6-phosphate by phosphoglucomutase before entering glycolysis. Glycogenolysis is stimulated by glucagon or epinephrine via the activation of phosphorylase kinase. Glycogen Metabolism 
  • Glucagon Glucagon A 29-amino acid pancreatic peptide derived from proglucagon which is also the precursor of intestinal glucagon-like peptides. Glucagon is secreted by pancreatic alpha cells and plays an important role in regulation of blood glucose concentration, ketone metabolism, and several other biochemical and physiological processes. Gastrointestinal Secretions release Release Release of a virus from the host cell following virus assembly and maturation. Egress can occur by host cell lysis, exocytosis, or budding through the plasma membrane. Virology
The conversion of proinsulin to insulin

The conversion of proinsulin to insulin Insulin Insulin is a peptide hormone that is produced by the beta cells of the pancreas. Insulin plays a role in metabolic functions such as glucose uptake, glycolysis, glycogenesis, lipogenesis, and protein synthesis. Exogenous insulin may be needed for individuals with diabetes mellitus, in whom there is a deficiency in endogenous insulin or increased insulin resistance. Insulin:
The A and B chains remain connected by disulfide bridges, while the C peptide is cleaved.

Image by Lecturio.

Pathophysiology of insulinomas

  • Insulinomas are functional neuroendocrine tumors Neuroendocrine tumors Tumors whose cells possess secretory granules and originate from the neuroectoderm, i.e., the cells of the ectoblast or epiblast that program the neuroendocrine system. Common properties across most neuroendocrine tumors include ectopic hormone production (often via apud cells), the presence of tumor-associated antigens, and isozyme composition. Gastrinoma derived from pancreatic islet cells.
  • Results in autonomously secreted insulin Insulin Insulin is a peptide hormone that is produced by the beta cells of the pancreas. Insulin plays a role in metabolic functions such as glucose uptake, glycolysis, glycogenesis, lipogenesis, and protein synthesis. Exogenous insulin may be needed for individuals with diabetes mellitus, in whom there is a deficiency in endogenous insulin or increased insulin resistance. Insulin even when plasma Plasma The residual portion of blood that is left after removal of blood cells by centrifugation without prior blood coagulation. Transfusion Products glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance concentration is low
  • Failure to suppress insulin Insulin Insulin is a peptide hormone that is produced by the beta cells of the pancreas. Insulin plays a role in metabolic functions such as glucose uptake, glycolysis, glycogenesis, lipogenesis, and protein synthesis. Exogenous insulin may be needed for individuals with diabetes mellitus, in whom there is a deficiency in endogenous insulin or increased insulin resistance. Insulin plus inhibited glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance synthesis Synthesis Polymerase Chain Reaction (PCR) hypoglycemia Hypoglycemia Hypoglycemia is an emergency condition defined as a serum glucose level ≤ 70 mg/dL (≤ 3.9 mmol/L) in diabetic patients. In nondiabetic patients, there is no specific or defined limit for normal serum glucose levels, and hypoglycemia is defined mainly by its clinical features. Hypoglycemia
  • A catecholamine response occurs → symptoms
  • ↓ Cerebral glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance neuroglycopenic symptoms Neuroglycopenic Symptoms Hypoglycemia

Clinical Presentation

Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship generally present with fasting hypoglycemia Hypoglycemia Hypoglycemia is an emergency condition defined as a serum glucose level ≤ 70 mg/dL (≤ 3.9 mmol/L) in diabetic patients. In nondiabetic patients, there is no specific or defined limit for normal serum glucose levels, and hypoglycemia is defined mainly by its clinical features. Hypoglycemia, which may manifest in episodes of sympathetic stimulation and/or central nervous system Central nervous system The main information-processing organs of the nervous system, consisting of the brain, spinal cord, and meninges. Nervous System: Anatomy, Structure, and Classification disturbances.

  • Symptoms of sympathetic activation:
    • Tremor Tremor Cyclical movement of a body part that can represent either a physiologic process or a manifestation of disease. Intention or action tremor, a common manifestation of cerebellar diseases, is aggravated by movement. In contrast, resting tremor is maximal when there is no attempt at voluntary movement, and occurs as a relatively frequent manifestation of parkinson disease. Myotonic Dystrophies
    • Pallor
    • Anxiety Anxiety Feelings or emotions of dread, apprehension, and impending disaster but not disabling as with anxiety disorders. Generalized Anxiety Disorder
    • Diaphoresis
    • Palpitations Palpitations Ebstein’s Anomaly
  • Neuroglycopenic symptoms Neuroglycopenic Symptoms Hypoglycemia:
    • Confusion
    • Blurred vision Blurred Vision Retinal Detachment
    • Ataxia Ataxia Impairment of the ability to perform smoothly coordinated voluntary movements. This condition may affect the limbs, trunk, eyes, pharynx, larynx, and other structures. Ataxia may result from impaired sensory or motor function. Sensory ataxia may result from posterior column injury or peripheral nerve diseases. Motor ataxia may be associated with cerebellar diseases; cerebral cortex diseases; thalamic diseases; basal ganglia diseases; injury to the red nucleus; and other conditions. Ataxia-telangiectasia
    • Seizures Seizures A seizure is abnormal electrical activity of the neurons in the cerebral cortex that can manifest in numerous ways depending on the region of the brain affected. Seizures consist of a sudden imbalance that occurs between the excitatory and inhibitory signals in cortical neurons, creating a net excitation. The 2 major classes of seizures are focal and generalized. Seizures
    • Coma Coma Coma is defined as a deep state of unarousable unresponsiveness, characterized by a score of 3 points on the GCS. A comatose state can be caused by a multitude of conditions, making the precise epidemiology and prognosis of coma difficult to determine. Coma

Diagnosis

Whipple triad Whipple triad A triad of findings that includes 1) a confirmed glucose concentration ≤ 70 mg/dl (≤ 3. 9 mmol/l), 2) signs and symptoms associated with hypoglycemia, and 3) the resolution of symptoms after the management of hypoglycemia. Hypoglycemia

A collection of criteria that signal that a patient’s symptoms are a result of hypoglycemia Hypoglycemia Hypoglycemia is an emergency condition defined as a serum glucose level ≤ 70 mg/dL (≤ 3.9 mmol/L) in diabetic patients. In nondiabetic patients, there is no specific or defined limit for normal serum glucose levels, and hypoglycemia is defined mainly by its clinical features. Hypoglycemia, which will be present in patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with an insulinoma Insulinoma A benign tumor of the pancreatic beta cells. Insulinoma secretes excess insulin resulting in hypoglycemia. Pancreatic Neuroendocrine Tumors (PanNETs):

  • ↓ Serum glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance
  • Symptoms of hypoglycemia Hypoglycemia Hypoglycemia is an emergency condition defined as a serum glucose level ≤ 70 mg/dL (≤ 3.9 mmol/L) in diabetic patients. In nondiabetic patients, there is no specific or defined limit for normal serum glucose levels, and hypoglycemia is defined mainly by its clinical features. Hypoglycemia
  • Resolution of symptoms after glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance administration

Laboratory evaluation

The following laboratory values can assist in the diagnosis. These may be performed during a 48- or 72-hour fasting evaluation:

  • ↓ Serum glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance level
  • Inappropriately ↑ serum insulin Insulin Insulin is a peptide hormone that is produced by the beta cells of the pancreas. Insulin plays a role in metabolic functions such as glucose uptake, glycolysis, glycogenesis, lipogenesis, and protein synthesis. Exogenous insulin may be needed for individuals with diabetes mellitus, in whom there is a deficiency in endogenous insulin or increased insulin resistance. Insulin
  • C-peptide C-peptide The middle segment of proinsulin that is between the n-terminal b-chain and the c-terminal a-chain. It is a pancreatic peptide of about 31 residues, depending on the species. Upon proteolytic cleavage of proinsulin, equimolar insulin and c-peptide are released. C-peptide immunoassay has been used to assess pancreatic beta cell function in diabetic patients with circulating insulin antibodies or exogenous insulin. Half-life of c-peptide is 30 min, almost 8 times that of insulin. Diabetes Mellitus
  • ↑ Proinsulin
  • Negative test for sulfonylureas Sulfonylureas Sulfonamides and Trimethoprim

MEN1 MEN1 A form of multiple endocrine neoplasia that is characterized by the combined occurrence of tumors in the parathyroid glands, the pituitary gland, and the pancreatic islets. The resulting clinical signs include hyperparathyroidism; hypercalcemia; hyperprolactinemia; cushing disease; gastrinoma; and zollinger-ellison syndrome. This disease is due to loss-of-function of the men1 gene, a tumor suppressor gene on chromosome 11 (locus: 11q13). Multiple Endocrine Neoplasia genetic testing Genetic Testing Detection of a mutation; genotype; karyotype; or specific alleles associated with genetic traits, heritable diseases, or predisposition to a disease, or that may lead to the disease in descendants. It includes prenatal genetic testing. Myotonic Dystrophies may be performed for: 

  • Young patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship
  • Family or personal history of other endocrinopathies 

Imaging

The following imaging modalities are useful for localizing the insulinoma Insulinoma A benign tumor of the pancreatic beta cells. Insulinoma secretes excess insulin resulting in hypoglycemia. Pancreatic Neuroendocrine Tumors (PanNETs) and preoperative planning:

  • CT or MRI of the abdomen:
    • Can detect 70%–85% of insulinomas
    • Findings:
      • Small, solid mass Mass Three-dimensional lesion that occupies a space within the breast Imaging of the Breast
      • Enhances with contrast
  • Nuclear imaging Nuclear Imaging Nuclear imaging is the radiologic examination using radiopharmaceuticals, which are radioactive substances taken up by specific types of cells. Nuclear medicine is more concerned with the functional and molecular aspects of the organ or pathology being investigated rather than the structure. Nuclear Imaging: used if conventional imaging is unremarkable
  • EGD with endoscopic ultrasound of the pancreas Pancreas The pancreas lies mostly posterior to the stomach and extends across the posterior abdominal wall from the duodenum on the right to the spleen on the left. This organ has both exocrine and endocrine tissue. Pancreas: Anatomy:
    • Invasive
    • May be utilized if CT and MRI are negative but a strong suspicion remains
Radiographic and surgical findings insulinoma

Radiographic and surgical findings for an insulinoma Insulinoma A benign tumor of the pancreatic beta cells. Insulinoma secretes excess insulin resulting in hypoglycemia. Pancreatic Neuroendocrine Tumors (PanNETs):
A: A large insulinoma Insulinoma A benign tumor of the pancreatic beta cells. Insulinoma secretes excess insulin resulting in hypoglycemia. Pancreatic Neuroendocrine Tumors (PanNETs) of the pancreatic tail was detected with combined CT and nuclear medicine Nuclear medicine A specialty field of radiology concerned with diagnostic, therapeutic, and investigative use of radioactive compounds. Nuclear Imaging imaging.
B: The gross appearance of the insulinoma Insulinoma A benign tumor of the pancreatic beta cells. Insulinoma secretes excess insulin resulting in hypoglycemia. Pancreatic Neuroendocrine Tumors (PanNETs) after it was resected laparoscopically

Image: “Preoperative Glucagon-like peptide-1 receptor Receptor Receptors are proteins located either on the surface of or within a cell that can bind to signaling molecules known as ligands (e.g., hormones) and cause some type of response within the cell. Receptors imaging reduces surgical trauma and pancreatic tissue loss in insulinoma Insulinoma A benign tumor of the pancreatic beta cells. Insulinoma secretes excess insulin resulting in hypoglycemia. Pancreatic Neuroendocrine Tumors (PanNETs) patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship: a report of three cases” by Wenning AS, Kirchner P, Antwi K, Fani M, Wild D, Christ E, Gloor B. License: CC BY 4.0

Management

Surgical resection

Removal of the insulinoma Insulinoma A benign tumor of the pancreatic beta cells. Insulinoma secretes excess insulin resulting in hypoglycemia. Pancreatic Neuroendocrine Tumors (PanNETs) is the treatment of choice and provides a favorable cure rate.

For resectable tumors (depending on tumor Tumor Inflammation location and number): 

  • Carries the most favorable prognosis Prognosis A prediction of the probable outcome of a disease based on a individual’s condition and the usual course of the disease as seen in similar situations. Non-Hodgkin Lymphomas
  • Enucleation of solitary tumors
  • Partial distal pancreatectomy 
  • Total pancreatectomy
  • Whipple procedure 

For metastatic disease to the liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy:

  • Resection
  • Cryotherapy Cryotherapy A form of therapy consisting in the local or general use of cold. The selective destruction of tissue by extreme cold or freezing is cryosurgery. Chondrosarcoma
  • Radiofrequency ablation Radiofrequency ablation Removal of tissue using heat generated from electrodes delivering an alternating electrical current in the frequency of radio waves. Hepatocellular Carcinoma (HCC) and Liver Metastases 
  • Embolization Embolization A method of hemostasis utilizing various agents such as gelfoam, silastic, metal, glass, or plastic pellets, autologous clot, fat, and muscle as emboli. It has been used in the treatment of spinal cord and intracranial arteriovenous malformations, renal arteriovenous fistulas, gastrointestinal bleeding, epistaxis, hypersplenism, certain highly vascular tumors, traumatic rupture of blood vessels, and control of operative hemorrhage. Gastrointestinal Bleeding 

Medical therapy

Medications to prevent symptomatic hypoglycemia Hypoglycemia Hypoglycemia is an emergency condition defined as a serum glucose level ≤ 70 mg/dL (≤ 3.9 mmol/L) in diabetic patients. In nondiabetic patients, there is no specific or defined limit for normal serum glucose levels, and hypoglycemia is defined mainly by its clinical features. Hypoglycemia may be used if the insulinoma Insulinoma A benign tumor of the pancreatic beta cells. Insulinoma secretes excess insulin resulting in hypoglycemia. Pancreatic Neuroendocrine Tumors (PanNETs) is unresectable or the patient is a poor surgical candidate.

  • Diazoxide:
    • Potassium Potassium An element in the alkali group of metals with an atomic symbol k, atomic number 19, and atomic weight 39. 10. It is the chief cation in the intracellular fluid of muscle and other cells. Potassium ion is a strong electrolyte that plays a significant role in the regulation of fluid volume and maintenance of the water-electrolyte balance. Hyperkalemia channel activator
    • Inhibits insulin Insulin Insulin is a peptide hormone that is produced by the beta cells of the pancreas. Insulin plays a role in metabolic functions such as glucose uptake, glycolysis, glycogenesis, lipogenesis, and protein synthesis. Exogenous insulin may be needed for individuals with diabetes mellitus, in whom there is a deficiency in endogenous insulin or increased insulin resistance. Insulin secretion Secretion Coagulation Studies
  • Octreotide Octreotide A potent, long-acting synthetic somatostatin octapeptide analog that inhibits secretion of growth hormone and is used to treat hormone-secreting tumors; diabetes mellitus; hypotension, orthostatic; hyperinsulinism; hypergastrinemia; and small bowel fistula. Antidiarrheal Drugs
    • Somatostatin Somatostatin A 14-amino acid peptide named for its ability to inhibit pituitary growth hormone release, also called somatotropin release-inhibiting factor. It is expressed in the central and peripheral nervous systems, the gut, and other organs. SRIF can also inhibit the release of thyroid-stimulating hormone; prolactin; insulin; and glucagon besides acting as a neurotransmitter and neuromodulator. In a number of species including humans, there is an additional form of somatostatin, srif-28 with a 14-amino acid extension at the n-terminal. Gastrointestinal Secretions analog
    • 2nd-line treatment after diazoxide
    • Can inhibit secretion Secretion Coagulation Studies of:
      • Insulin Insulin Insulin is a peptide hormone that is produced by the beta cells of the pancreas. Insulin plays a role in metabolic functions such as glucose uptake, glycolysis, glycogenesis, lipogenesis, and protein synthesis. Exogenous insulin may be needed for individuals with diabetes mellitus, in whom there is a deficiency in endogenous insulin or increased insulin resistance. Insulin
      • Glucagon Glucagon A 29-amino acid pancreatic peptide derived from proglucagon which is also the precursor of intestinal glucagon-like peptides. Glucagon is secreted by pancreatic alpha cells and plays an important role in regulation of blood glucose concentration, ketone metabolism, and several other biochemical and physiological processes. Gastrointestinal Secretions
      • Gastrin Gastrin A family of gastrointestinal peptide hormones that excite the secretion of gastric juice. They may also occur in the central nervous system where they are presumed to be neurotransmitters. Gastrointestinal Secretions

Differential Diagnosis

  • Factitious hypoglycemia Hypoglycemia Hypoglycemia is an emergency condition defined as a serum glucose level ≤ 70 mg/dL (≤ 3.9 mmol/L) in diabetic patients. In nondiabetic patients, there is no specific or defined limit for normal serum glucose levels, and hypoglycemia is defined mainly by its clinical features. Hypoglycemia: may result from exogenous self-administration of insulin Insulin Insulin is a peptide hormone that is produced by the beta cells of the pancreas. Insulin plays a role in metabolic functions such as glucose uptake, glycolysis, glycogenesis, lipogenesis, and protein synthesis. Exogenous insulin may be needed for individuals with diabetes mellitus, in whom there is a deficiency in endogenous insulin or increased insulin resistance. Insulin. Factitious hypoglycemia Hypoglycemia Hypoglycemia is an emergency condition defined as a serum glucose level ≤ 70 mg/dL (≤ 3.9 mmol/L) in diabetic patients. In nondiabetic patients, there is no specific or defined limit for normal serum glucose levels, and hypoglycemia is defined mainly by its clinical features. Hypoglycemia is often seen with healthcare workers who present with symptoms of hypoglycemia Hypoglycemia Hypoglycemia is an emergency condition defined as a serum glucose level ≤ 70 mg/dL (≤ 3.9 mmol/L) in diabetic patients. In nondiabetic patients, there is no specific or defined limit for normal serum glucose levels, and hypoglycemia is defined mainly by its clinical features. Hypoglycemia. Unlike insulinomas, a laboratory evaluation will reveal low C-peptide C-peptide The middle segment of proinsulin that is between the n-terminal b-chain and the c-terminal a-chain. It is a pancreatic peptide of about 31 residues, depending on the species. Upon proteolytic cleavage of proinsulin, equimolar insulin and c-peptide are released. C-peptide immunoassay has been used to assess pancreatic beta cell function in diabetic patients with circulating insulin antibodies or exogenous insulin. Half-life of c-peptide is 30 min, almost 8 times that of insulin. Diabetes Mellitus and proinsulin levels despite high insulin Insulin Insulin is a peptide hormone that is produced by the beta cells of the pancreas. Insulin plays a role in metabolic functions such as glucose uptake, glycolysis, glycogenesis, lipogenesis, and protein synthesis. Exogenous insulin may be needed for individuals with diabetes mellitus, in whom there is a deficiency in endogenous insulin or increased insulin resistance. Insulin levels. Management includes correcting hypoglycemia Hypoglycemia Hypoglycemia is an emergency condition defined as a serum glucose level ≤ 70 mg/dL (≤ 3.9 mmol/L) in diabetic patients. In nondiabetic patients, there is no specific or defined limit for normal serum glucose levels, and hypoglycemia is defined mainly by its clinical features. Hypoglycemia and psychiatric therapy.
  • Sulfonylurea toxicity Toxicity Dosage Calculation: may occur in patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship who are not eating or have renal impairment. Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship will present with hypoglycemia Hypoglycemia Hypoglycemia is an emergency condition defined as a serum glucose level ≤ 70 mg/dL (≤ 3.9 mmol/L) in diabetic patients. In nondiabetic patients, there is no specific or defined limit for normal serum glucose levels, and hypoglycemia is defined mainly by its clinical features. Hypoglycemia. Unlike with insulinomas, serum sulfonylurea testing will be positive. Management includes withdrawal of the causative agent and treatment for hypoglycemia Hypoglycemia Hypoglycemia is an emergency condition defined as a serum glucose level ≤ 70 mg/dL (≤ 3.9 mmol/L) in diabetic patients. In nondiabetic patients, there is no specific or defined limit for normal serum glucose levels, and hypoglycemia is defined mainly by its clinical features. Hypoglycemia.
  • Persistent hyperinsulinemic hypoglycemia Hypoglycemia Hypoglycemia is an emergency condition defined as a serum glucose level ≤ 70 mg/dL (≤ 3.9 mmol/L) in diabetic patients. In nondiabetic patients, there is no specific or defined limit for normal serum glucose levels, and hypoglycemia is defined mainly by its clinical features. Hypoglycemia of infancy (PHHI): most common cause of persistent hypoglycemia Hypoglycemia Hypoglycemia is an emergency condition defined as a serum glucose level ≤ 70 mg/dL (≤ 3.9 mmol/L) in diabetic patients. In nondiabetic patients, there is no specific or defined limit for normal serum glucose levels, and hypoglycemia is defined mainly by its clinical features. Hypoglycemia in neonates and infants, caused by mutations involving different proteins Proteins Linear polypeptides that are synthesized on ribosomes and may be further modified, crosslinked, cleaved, or assembled into complex proteins with several subunits. The specific sequence of amino acids determines the shape the polypeptide will take, during protein folding, and the function of the protein. Energy Homeostasis leading to insulin Insulin Insulin is a peptide hormone that is produced by the beta cells of the pancreas. Insulin plays a role in metabolic functions such as glucose uptake, glycolysis, glycogenesis, lipogenesis, and protein synthesis. Exogenous insulin may be needed for individuals with diabetes mellitus, in whom there is a deficiency in endogenous insulin or increased insulin resistance. Insulin release Release Release of a virus from the host cell following virus assembly and maturation. Egress can occur by host cell lysis, exocytosis, or budding through the plasma membrane. Virology dysregulation. A laboratory evaluation will show inappropriately detectable levels of insulin Insulin Insulin is a peptide hormone that is produced by the beta cells of the pancreas. Insulin plays a role in metabolic functions such as glucose uptake, glycolysis, glycogenesis, lipogenesis, and protein synthesis. Exogenous insulin may be needed for individuals with diabetes mellitus, in whom there is a deficiency in endogenous insulin or increased insulin resistance. Insulin and C-peptide C-peptide The middle segment of proinsulin that is between the n-terminal b-chain and the c-terminal a-chain. It is a pancreatic peptide of about 31 residues, depending on the species. Upon proteolytic cleavage of proinsulin, equimolar insulin and c-peptide are released. C-peptide immunoassay has been used to assess pancreatic beta cell function in diabetic patients with circulating insulin antibodies or exogenous insulin. Half-life of c-peptide is 30 min, almost 8 times that of insulin. Diabetes Mellitus, low beta-hydroxybutyrate Beta-hydroxybutyrate Butyric acid substituted in the beta or 3 position. It is one of the ketone bodies produced in the liver. Ketone Body Metabolism and free fatty acids Acids Chemical compounds which yield hydrogen ions or protons when dissolved in water, whose hydrogen can be replaced by metals or basic radicals, or which react with bases to form salts and water (neutralization). An extension of the term includes substances dissolved in media other than water. Acid-Base Balance, and a glycemic response to glucagon Glucagon A 29-amino acid pancreatic peptide derived from proglucagon which is also the precursor of intestinal glucagon-like peptides. Glucagon is secreted by pancreatic alpha cells and plays an important role in regulation of blood glucose concentration, ketone metabolism, and several other biochemical and physiological processes. Gastrointestinal Secretions. Genetic testing Genetic Testing Detection of a mutation; genotype; karyotype; or specific alleles associated with genetic traits, heritable diseases, or predisposition to a disease, or that may lead to the disease in descendants. It includes prenatal genetic testing. Myotonic Dystrophies is often performed. Management may include diazoxide, octreotide Octreotide A potent, long-acting synthetic somatostatin octapeptide analog that inhibits secretion of growth hormone and is used to treat hormone-secreting tumors; diabetes mellitus; hypotension, orthostatic; hyperinsulinism; hypergastrinemia; and small bowel fistula. Antidiarrheal Drugs, or surgery.
  • Insulin Insulin Insulin is a peptide hormone that is produced by the beta cells of the pancreas. Insulin plays a role in metabolic functions such as glucose uptake, glycolysis, glycogenesis, lipogenesis, and protein synthesis. Exogenous insulin may be needed for individuals with diabetes mellitus, in whom there is a deficiency in endogenous insulin or increased insulin resistance. Insulin autoimmune hypoglycemia Hypoglycemia Hypoglycemia is an emergency condition defined as a serum glucose level ≤ 70 mg/dL (≤ 3.9 mmol/L) in diabetic patients. In nondiabetic patients, there is no specific or defined limit for normal serum glucose levels, and hypoglycemia is defined mainly by its clinical features. Hypoglycemia: occurs in patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship who have autoantibodies Autoantibodies Antibodies that react with self-antigens (autoantigens) of the organism that produced them. Blotting Techniques directed to endogenous insulin Insulin Insulin is a peptide hormone that is produced by the beta cells of the pancreas. Insulin plays a role in metabolic functions such as glucose uptake, glycolysis, glycogenesis, lipogenesis, and protein synthesis. Exogenous insulin may be needed for individuals with diabetes mellitus, in whom there is a deficiency in endogenous insulin or increased insulin resistance. Insulin or the insulin Insulin Insulin is a peptide hormone that is produced by the beta cells of the pancreas. Insulin plays a role in metabolic functions such as glucose uptake, glycolysis, glycogenesis, lipogenesis, and protein synthesis. Exogenous insulin may be needed for individuals with diabetes mellitus, in whom there is a deficiency in endogenous insulin or increased insulin resistance. Insulin receptor Receptor Receptors are proteins located either on the surface of or within a cell that can bind to signaling molecules known as ligands (e.g., hormones) and cause some type of response within the cell. Receptors, which results in hypoglycemia Hypoglycemia Hypoglycemia is an emergency condition defined as a serum glucose level ≤ 70 mg/dL (≤ 3.9 mmol/L) in diabetic patients. In nondiabetic patients, there is no specific or defined limit for normal serum glucose levels, and hypoglycemia is defined mainly by its clinical features. Hypoglycemia. Detection of antibodies Antibodies Immunoglobulins (Igs), also known as antibodies, are glycoprotein molecules produced by plasma cells that act in immune responses by recognizing and binding particular antigens. The various Ig classes are IgG (the most abundant), IgM, IgE, IgD, and IgA, which differ in their biologic features, structure, target specificity, and distribution. Immunoglobulins: Types and Functions to insulin Insulin Insulin is a peptide hormone that is produced by the beta cells of the pancreas. Insulin plays a role in metabolic functions such as glucose uptake, glycolysis, glycogenesis, lipogenesis, and protein synthesis. Exogenous insulin may be needed for individuals with diabetes mellitus, in whom there is a deficiency in endogenous insulin or increased insulin resistance. Insulin will provide the diagnosis. This condition is managed with small, frequent meals; steroids Steroids A group of polycyclic compounds closely related biochemically to terpenes. They include cholesterol, numerous hormones, precursors of certain vitamins, bile acids, alcohols (sterols), and certain natural drugs and poisons. Steroids have a common nucleus, a fused, reduced 17-carbon atom ring system, cyclopentanoperhydrophenanthrene. Most steroids also have two methyl groups and an aliphatic side-chain attached to the nucleus. Benign Liver Tumors; and, in severe cases, plasmapheresis Plasmapheresis Procedure whereby plasma is separated and extracted from anticoagulated whole blood and the red cells retransfused to the donor. Plasmapheresis is also employed for therapeutic use. Stevens-Johnson Syndrome.

References

  1. Vella, A. (2021). Insulinoma. In Mulder, J.E. (Ed.). UpToDate. Retrieved April 13, 2021, from https://www.uptodate.com/contents/insulinoma
  2. Service, FJ, et al. (1991). Functioning insulinoma—Incidence, recurrence, and long-term survival of patients: A 60-year study. Mayo Clinic Proceedings. 66(7), 711–19. https://pubmed.ncbi.nlm.nih.gov/1677058/
  3. Kavlie, H, White, TT. (1972). Pancreatic islet beta cell tumors and hyperplasia: Experience in 14 Seattle hospitals. Annals of Surgery. 175(3), 326–35. https://pubmed.ncbi.nlm.nih.gov/4342703/
  4. Lupsa, BC, et al. (2009). Autoimmune forms of hypoglycemia. Medicine. 88(3), 141–53. https://pubmed.ncbi.nlm.nih.gov/19440117/
  5. Nguyen, M. (2021). Insulinoma. MSD Manual Professional Version. Retrieved April 18, 2021, from https://www.msdmanuals.com/professional/gastrointestinal-disorders/tumors-of-the-gastrointestinal-tract/insulinoma
  6. Zhuo, F, and Anastasopoulou, C. (2020). Insulinoma. StatPearls. Retrieved April 18, 2021, from https://www.ncbi.nlm.nih.gov/books/NBK544299/
  7. Ali, ZA. (2020). Insulinoma. In Radhakrishnan, N. (Ed.). Medscape. Retrieved April 18, 2021, from https://emedicine.medscape.com/article/283039-overview

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