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Proteins are 1 of the 3 primary macronutrients in the body and are synthesized from individual building blocks called amino acids (AAs). Amino acids are bound together by peptide bonds, which link the amino end of one AA to the carboxy end of the next AA, generating a protein's primary structure. The strand of AAs then undergoes additional folding, ultimately generating complex 3-dimensional structures. Proteins have a wide variety of functions, including catalytic, structural, regulatory, transport, storage, and immunologic functions. They are digested by proteases and peptidases secreted by the stomach and pancreas and absorbed as individual AAs in the small intestines through specialized transporters. There are countless medical conditions related to protein abnormalities, including abnormalities related to enzymes, receptors, membrane channels, hormones, accumulation of proteins, and autoimmune disorders.

Pituitary Adenomas

Pituitary adenomas are tumors that develop within the anterior lobe of the pituitary gland. They are classified by size (either micro- or macroadenomas) and by their ability to secrete hormones. Non-functioning or non-secretory adenomas do not secrete hormones but can compress surrounding pituitary tissue, leading to hypopituitarism. Secretory adenomas secrete various hormones depending on the cell type from which they evolved, leading to hyperpituitarism.

Congestive Heart Failure

Congestive heart failure refers to the inability of the heart to supply the body with normal cardiac output to meet metabolic needs. Echocardiography can confirm the diagnosis and give information about the ejection fraction. Treatment is directed at the removal of excess fluid and decreasing oxygen demand of the heart. Prognosis depends on the underlying cause, compliance with medical therapy, and presence of comorbidities.

Cirrhosis

Cirrhosis is a late stage of hepatic parenchymal necrosis and scarring (fibrosis) most commonly due to hepatitis C infection and alcoholic liver disease. Patients may present with jaundice, ascites, and hepatosplenomegaly. Cirrhosis can also cause complications such as hepatic encephalopathy, portal hypertension, portal vein thrombosis, and hepatorenal syndrome. Diagnosis is clinical. Management requires treating the underlying disease, managing complications, and, if required, liver transplantation.

Acromegaly and Gigantism

Acromegaly and gigantism are caused by an excessive production of growth hormone (GH) by the pituitary gland. Tall stature is a clinical sign observed in some patients with gigantism. Increased GH and insulin-like growth factor-1 (IGF-1) are responsible for inducing hypersomatotropism. Acromegaly is usually produced by pituitary tumors secreting GH or, less commonly, by extrapituitary disorders. Gigantism typically results in children from excess GH before growth-plate closure; acromegaly typically results from excess GH after growth-plate closure. Diagnosis involves neuroimaging of the pituitary and laboratory tests to evaluate the hypothalamic-pituitary axis. Treatment depends on the operative status of the tumor (if present), or a nonoperative treatment strategy may be utilized.

Hormones: Overview

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. The work of hormones allows the body to maintain homeostasis and regulate growth and development. Hormones are typically either made from amino acids or derived from cholesterol (the latter group being known as steroid hormones). Hormones exert their effects by binding to receptors either on the cell surface (most amino acid–based hormones) or within the cytosol (steroid hormones). Ultimately, binding to receptors triggers changes in gene expression or enzymatic activity within the cell.

Pituitary Gland

The pituitary gland, also known as the hypophysis, is considered the “master endocrine gland” because it releases hormones that regulate the activity of multiple major endocrine organs in the body. The gland sits on the sella turcica, just below the hypothalamus, which is the primary regulator of the pituitary gland. The pituitary gland has 2 lobes: the anterior lobe (the adenohypophysis) and the posterior lobe (the neurohypophysis). Each lobe has its own regulation, set of secretory products, and feedback loops. Abnormalities in the pituitary gland can lead to a wide range of clinical conditions, some of which include hyperprolactinemia, acromegaly, hyperthyroidism or hypothyroidism, and central diabetes insipidus.

Hypothalamus

The hypothalamus is a collection of various nuclei within the diencephalon in the center of the brain. The hypothalamus plays a vital role in endocrine regulation as the primary regulator of the pituitary gland, and it is the major point of integration between the central nervous and endocrine systems. Different nuclei within the hypothalamus play roles in hormone regulation and secretion, autonomic regulation, thermoregulation, food and water intake, sleep and circadian rhythms, memory, and emotional behavior. The hypothalamus has both neural and circulatory connections with the pituitary gland. Abnormalities in the hypothalamus can lead to a wide range of clinical conditions.

Hypopituitarism

Hypopituitarism is a condition characterized by pituitary hormone deficiency. This condition primarily results from a disease of the pituitary gland, but it may arise from hypothalamic dysfunction. Pituitary tumors are one of the most common causes. The majority of cases affect the anterior pituitary lobe (adenohypophysis), which accounts for 80% of the gland. The hormones produced from this lobe are growth hormone, follicle-stimulating hormone, luteinizing hormone, thyroid-stimulating hormone (TSH), adrenocorticotropic hormone, and prolactin. When the posterior lobe (neurohypophysis) is also damaged, loss of antidiuretic hormone and oxytocin occurs. All of these hormones regulate the activities of different organs, and thus the effects of pituitary hypofunction are multisystemic. The diagnosis is made through a combination of clinical findings, hormone levels, provocation tests, and brain imaging. Treatment is hormone replacement and addressing the etiology.

Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH)

Syndrome of inappropriate antidiuretic hormone secretion (SIADH) is a disorder of impaired water excretion due to the inability to suppress the secretion of antidiuretic hormone (ADH). The inappropriate secretion of ADH can be due to various causes, including increased production by the pituitary gland due to trauma, disease, or certain medications; the ectopic secretion of ADH by cancer; or hereditary causes (nephrogenic SIADH). Syndrome of inappropriate antidiuretic hormone secretion is characterized by impaired water excretion leading to dilutional hyponatremia, which is mainly asymptomatic but may cause neurologic symptoms. Syndrome of inappropriate antidiuretic hormone secretion should be suspected in any patient with hyponatremia, hypo-osmolality, and high urine osmolality.

Hyperprolactinemia

Hyperprolactinemia is defined as a condition of elevated levels of prolactin (PRL) hormone in the blood. The PRL hormone is secreted by the anterior pituitary gland and is responsible for breast development and lactation. Many factors contribute to the development of hyperprolactinemia. The most common cause is PRL-secreting pituitary adenomas (prolactinomas). Diagnosis is achieved through hormonal testing to rule out other endocrine conditions and confirmatory imaging tests. Dopamine agonists are the 1st-line drugs for treatment. Refractory cases require surgery and possibly radiation therapy.

Diabetes Insipidus

Diabetes insipidus (DI) is a condition in which the kidneys are unable to concentrate urine. There are 2 subforms of DI: central DI (CDI) and nephrogenic DI (NDI). In CDI, the amount of antidiuretic hormone (ADH) produced by the hypothalamus or released from the pituitary gland is decreased. In nephrogenic DI, the kidneys fail to respond to circulating ADH. Both conditions result in the kidneys being unable to concentrate urine, leading to polyuria, nocturia, and polydipsia. Central and NDI are differentiated based on measured ADH levels and response to a water deprivation test. Central DI is treated with desmopressin, while nephrogenic DI is treated with diuretics and dietary salt restriction.

Actions of ADH 05:24 min

Actions of ADH 4 quiz questions

Actions of ADH 2 Concept Pages
Dysregulation of ADH 04:02 min

Dysregulation of ADH 3 quiz questions

Dysregulation of ADH 2 Concept Pages
Central Diabetes Insipidus 09:03 min

Central Diabetes Insipidus 5 quiz questions

Central Diabetes Insipidus 1 concept page
SIADH: Clinical Presentation 05:55 min

SIADH: Clinical Presentation 5 quiz questions

SIADH: Clinical Presentation 1 concept page
SIADH: Diagnosis and Treatment 05:09 min

SIADH: Diagnosis and Treatment 4 quiz questions

SIADH: Diagnosis and Treatment 1 concept page
Arginine Vasopressin (AVP) Differential Diagnoses 09:43 min

Arginine Vasopressin (AVP) Differential Diagnoses 6 quiz questions

Arginine Vasopressin (AVP) Differential Diagnoses 4 Concept Pages
Cell Types 03:46 min

Cell Types 3 quiz questions

Cell Types 2 Concept Pages
Types of Peptide Hormones 11:25 min

Types of Peptide Hormones 6 quiz questions

Types of Peptide Hormones 2 Concept Pages
Hypothalamic Hormones 10:13 min

Hypothalamic Hormones 4 quiz questions

Hypothalamic Hormones 2 Concept Pages
Hypopituitarism 12:35 min

Hypopituitarism 5 quiz questions

Hypopituitarism 3 Concept Pages
Pituitary Apoplexy and Sheehan’s Syndrome 04:08 min

Pituitary Apoplexy and Sheehan’s Syndrome 3 quiz questions

Pituitary Apoplexy and Sheehan’s Syndrome 2 Concept Pages
Pituitary Sellar Masses 09:24 min

Pituitary Sellar Masses 4 quiz questions

Pituitary Sellar Masses 3 Concept Pages
Hyperprolactinemia 20:52 min

Hyperprolactinemia 6 quiz questions

Hyperprolactinemia 2 Concept Pages
Control of Growth Hormone Release 11:26 min

Control of Growth Hormone Release 6 quiz questions

Control of Growth Hormone Release 3 Concept Pages
Acromegaly (Growth Hormone Excess) 08:31 min

Acromegaly (Growth Hormone Excess) 5 quiz questions

Acromegaly (Growth Hormone Excess) 3 Concept Pages

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Pituitary Gland Disorders

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Your Educators of course Pituitary Gland Disorders

Carlo Raj, MD

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