Puberty

Puberty is a complex series of physical, psychosocial, and cognitive transitions usually experienced by adolescents (11–19 years of age). Puberty is marked by a growth in stature and the development of secondary sexual characteristics, achievement of fertility, and changes in most body systems. Being familiar with normal puberty is important to be able to recognize and manage abnormalities such as precocious puberty Precocious puberty Precocious puberty (PP) is the appearance of secondary sexual characteristics due to elevated sex hormones before the age of 6-8 in girls and 9 in boys. Excess hormone secretion may occur only at the level of the sex hormone or may involve the whole hypothalamic-pituitary-gonadal axis. Precocious Puberty or delayed puberty Delayed Puberty Delayed puberty (DP) is defined as the lack of testicular growth in boys past the age of 14 and the lack of thelarche in girls past the age of 13. Delayed puberty affects up to 5% of healthy boys and girls, and half of all cases are due to constitutional growth delay. Delayed Puberty.

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Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

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Overview

Definition

Puberty is the time period from the 1st appearance of secondary sexual characteristics until achieving complete sexual development. Puberty involves a complex series of physical, psychosocial, and cognitive changes.

Onset

  • Median age of the onset of puberty has decreased in recent years.
  • Range:
    • 8–13 years in girls 
    • 8–12 years in boys

Hormonal control in the initiation of puberty

  • A critical event in puberty is an increase in the pulsatile secretion of gonadotropin-releasing hormone (GnRH) from the arcuate nucleus in the hypothalamus 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. Hypothalamus.
    • Kisseptin neurons in the arcuate nucleus release neurokinin B and dynorphin.
    • Neurokinin B and dynorphin cause the pulsatile secretion of GnRH.
  • GnRH causes the release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from the anterior pituitary gland 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. Pituitary Gland. Both LH and FSH affect the Leydig and Sertoli cells in the testes and the theca and granulosa cells of the ovary.
  • Zona reticularis of the adrenal glands Adrenal Glands The adrenal glands are a pair of retroperitoneal endocrine glands located above the kidneys. The outer parenchyma is called the adrenal cortex and has 3 distinct zones, each with its own secretory products. Beneath the cortex lies the adrenal medulla, which secretes catecholamines involved in the fight-or-flight response. Adrenal Glands secretes androgens Androgens Androgens are naturally occurring steroid hormones responsible for development and maintenance of the male sex characteristics, including penile, scrotal, and clitoral growth, development of sexual hair, deepening of the voice, and musculoskeletal growth. Androgens and Antiandrogens such as DHEA, resulting in the characteristics of adrenarche. Zona reticularis functions separately from the hypothalamic-pituitary-gonadal axis.
  • Hormonal changes in girls:
    • LH acts on the theca cells of the ovary to convert cholesterol into androgens Androgens Androgens are naturally occurring steroid hormones responsible for development and maintenance of the male sex characteristics, including penile, scrotal, and clitoral growth, development of sexual hair, deepening of the voice, and musculoskeletal growth. Androgens and Antiandrogens.
    • Granulosa cell converts the androgens Androgens Androgens are naturally occurring steroid hormones responsible for development and maintenance of the male sex characteristics, including penile, scrotal, and clitoral growth, development of sexual hair, deepening of the voice, and musculoskeletal growth. Androgens and Antiandrogens to estradiol under the control of FSH signaling. 
    • Estradiol acts on various organs until the completion of puberty.
  • Hormonal changes in boys:
    • LH acts on Leydig cells to convert cholesterol into testosterone.
Development of the normal hypothalamic–pituitary–gonadal (hpg) axis in females

Normal hypothalamic–pituitary–gonadal (HPG) axis in females

GnRH: gonadotropin-releasing hormone
FSH: follicle-stimulating hormone
LH: leutinizing hormone
Image by Lecturio. License: CC BY-NC-SA 4.0

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Physical Changes During Puberty

Puberty can be divided into 4 different consecutive stages, namely, thelarche, pubarche, growth spurt, and menarche.

Thelarche

  • Breast development with formation of the breast bud and proliferation of the duct and gland epithelium Epithelium The epithelium is a complex of specialized cellular organizations arranged into sheets and lining cavities and covering the surfaces of the body. The cells exhibit polarity, having an apical and a basal pole. Structures important for the epithelial integrity and function involve the basement membrane, the semipermeable sheet on which the cells rest, and interdigitations, as well as cellular junctions. Surface Epithelium
  • 1st sign of puberty in girls
  • Participating 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: estrogen, estradiol, prolactin
  • Onset: 7–14 years of age

Pubarche

  • Growth of pubic and armpit hair
  • Participating 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: testosterone, 5α-dihydrotestosterone
  • Onset: 8–15 years of age

Growth spurt

  • Onset:
    • On average, 2 years earlier in girls than boys 
    • Approximately 1 year after the 1st indicators of puberty
  • 3–10 cm of growth per year
  • Participating 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:
    • Release of sex steroids leads to the production of growth 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.
    • Leads to production 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-like growth factor-1 in 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

Menarche

  • 1st menstrual bleeding
  • Due to estrogen withdrawal without preceding ovulation
  • Onset:
    • Between 9 and 16 years of age
    • Approximately 1 year after a growth spurt
  • Normally occurs later than other signs of puberty.

Tanner Stages of Development

“Tanner staging Staging Cancer is the 2nd leading cause of death in the US after cardiovascular disease. Many malignancies are treatable or curable, but some may recur. Thus, all malignancies must be assigned a grade and stage in order to guide management and determine prognosis. Grading, Staging, and Metastasis” is a scale that measures the physical/sexual development in children and adolescents. This staging Staging Cancer is the 2nd leading cause of death in the US after cardiovascular disease. Many malignancies are treatable or curable, but some may recur. Thus, all malignancies must be assigned a grade and stage in order to guide management and determine prognosis. Grading, Staging, and Metastasis technique involves the evaluation of genitalia in males, breast in females, and pubic hair in both.

Table: Tanner stages in females
Tanner 1 Tanner 2 Tanner 3 Tanner 4 Tanner 5
Age Prepubertal 8–11.5 years 11.5–13 years 12–15 years > 15 years
Pubic hair Villus hair only Sparse hair along the labia Coarse and curly hair covers the pubis. Adult hair that does not spread to the thigh Thigh The thigh is the region of the lower limb found between the hip and the knee joint. There is a single bone in the thigh called the femur, which is surrounded by large muscles grouped into 3 fascial compartments. Thigh Adult hair reaching the thigh Thigh The thigh is the region of the lower limb found between the hip and the knee joint. There is a single bone in the thigh called the femur, which is surrounded by large muscles grouped into 3 fascial compartments. Thigh
Breasts Breasts The breasts are found on the anterior thoracic wall and consist of mammary glands surrounded by connective tissue. The mammary glands are modified apocrine sweat glands that produce milk, which serves as nutrition for infants. Breasts are rudimentary and usually nonfunctioning in men. Breasts Elevation of papilla only Breast buds are palpable (1st sign of puberty in females) and areolae are enlarged. Breast tissue grows with no contour or separation. Breasts Breasts The breasts are found on the anterior thoracic wall and consist of mammary glands surrounded by connective tissue. The mammary glands are modified apocrine sweat glands that produce milk, which serves as nutrition for infants. Breasts are rudimentary and usually nonfunctioning in men. Breasts enlarge and areolae form secondary mound on the breast. Adult breast contours are present. Only the papilla is raised.
Other observations Adrenarche and ovarian growth Clitoral enlargement, labial pigmentation, growth of uterus Axillary hair, acne Menarche and development of menses Adult genitalia
Table: Tanner stages in males
Tanner 1 Tanner 2 Tanner 3 Tanner 4 Tanner 5
Age Prepubertal 8–11.5 years 11.5–13 years 12–15 years > 15 years
Pubic hair Villus hair only Sparse hair at base of the penis Penis The penis is the male organ of copulation and micturition. The organ is composed of a root, body, and glans. The root is attached to the pubic bone by the crura penis. The body consists of the 2 parallel corpora cavernosa and the corpus spongiosum. The glans is ensheathed by the prepuce or foreskin. Penis Coarse and curly hair appears over the pubis. Adult-quality hair in the pubic area, sparing the thigh Thigh The thigh is the region of the lower limb found between the hip and the knee joint. There is a single bone in the thigh called the femur, which is surrounded by large muscles grouped into 3 fascial compartments. Thigh Adult-quality hair in the pubic area, reaching the thigh Thigh The thigh is the region of the lower limb found between the hip and the knee joint. There is a single bone in the thigh called the femur, which is surrounded by large muscles grouped into 3 fascial compartments. Thigh
Genitalia
  • Testes < 2 cm
  • No growth of the penis Penis The penis is the male organ of copulation and micturition. The organ is composed of a root, body, and glans. The root is attached to the pubic bone by the crura penis. The body consists of the 2 parallel corpora cavernosa and the corpus spongiosum. The glans is ensheathed by the prepuce or foreskin. Penis
  • Testes: 2.5–3.2 cm
  • Thinning and reddening of the scrotum
  • Testes: 3.3–4 cm
  • Increase in length of the penis Penis The penis is the male organ of copulation and micturition. The organ is composed of a root, body, and glans. The root is attached to the pubic bone by the crura penis. The body consists of the 2 parallel corpora cavernosa and the corpus spongiosum. The glans is ensheathed by the prepuce or foreskin. Penis
  • Testes: 4.1–4.5 cm
  • Growth of the penis Penis The penis is the male organ of copulation and micturition. The organ is composed of a root, body, and glans. The root is attached to the pubic bone by the crura penis. The body consists of the 2 parallel corpora cavernosa and the corpus spongiosum. The glans is ensheathed by the prepuce or foreskin. Penis, darkening of the scrotum
  • Testes > 4.5 cm
  • Adult genital size
Other observations Adrenarche Decrease in body fat Gynecomastia Gynecomastia Gynecomastia is a benign proliferation of male breast glandular ductal tissue, usually bilateral, caused by increased estrogen activity, decreased testosterone activity, or medications. The condition is common and physiological in neonates, adolescent boys, and elderly men. Gynecomastia, breaking of voice, increased muscle mass Axillary hair, voice change, acne Facial hair, increase in muscle mass

Clinical Relevance

  • Iron deficiency anemia Iron Deficiency Anemia Iron deficiency anemia is the most common type of anemia worldwide. This form of anemia is caused by insufficient iron due to a decreased supply, an increased loss, or an increased demand. Iron deficiency anemia is seen across all ages, sexes, and socioeconomic strata; however, children, women of childbearing age, and patients from lower socioeconomic strata are at higher risk. Iron Deficiency Anemia: a condition affecting adolescent girls due to menstrual bleeding and insufficient iron intake. Males are less prone to anemia because testosterone increases erythropoiesis Erythropoiesis Erythropoiesis starts with hematopoietic stem cells, which develop into lineage-committed progenitors and differentiate into mature RBCs. The process occurs in stages, and extrusion of the nuclei and organelles occurs prior to maturation. Thus, mature RBCs lack nuclei and have a biconcave shape. Erythrocytes.
  • Gynecomastia Gynecomastia Gynecomastia is a benign proliferation of male breast glandular ductal tissue, usually bilateral, caused by increased estrogen activity, decreased testosterone activity, or medications. The condition is common and physiological in neonates, adolescent boys, and elderly men. Gynecomastia: enlargement or swelling of the breast tissue in men. Gynecomastia Gynecomastia Gynecomastia is a benign proliferation of male breast glandular ductal tissue, usually bilateral, caused by increased estrogen activity, decreased testosterone activity, or medications. The condition is common and physiological in neonates, adolescent boys, and elderly men. Gynecomastia affects approximately 50% of teenage boys at an average age of 13 years. Gynecomastia Gynecomastia Gynecomastia is a benign proliferation of male breast glandular ductal tissue, usually bilateral, caused by increased estrogen activity, decreased testosterone activity, or medications. The condition is common and physiological in neonates, adolescent boys, and elderly men. Gynecomastia is caused by the increased production or action of estrogens, enhanced breast-tissue sensitivity to estrogens, or the decreased production or action of androgens Androgens Androgens are naturally occurring steroid hormones responsible for development and maintenance of the male sex characteristics, including penile, scrotal, and clitoral growth, development of sexual hair, deepening of the voice, and musculoskeletal growth. Androgens and Antiandrogens.
  • Acne vulgaris Acne vulgaris Acne vulgaris, also known as acne, is a common disorder of the pilosebaceous units in adolescents and young adults. The condition occurs due to follicular hyperkeratinization, excess sebum production, follicular colonization by Cutibacterium acnes, and inflammation. Acne Vulgaris: a disorder of the pilosebaceous unit due to follicular hyperkeratinization, excess sebum production, follicular colonization by Cutibacterium acnes, and inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body's defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation. Severity of acne is associated with high serum levels of dehydroepiandrosterone sulfate.
  • Dysfunctional uterine bleeding: excessive, prolonged, and/or irregular endometrial bleeding, often seen during the 1st year of menarche. Dysfunctional uterine bleeding occurs due to anovulatory cycles as a result of the immature hypothalamic-pituitary-ovarian (HPO) axis, which fails to produce gonadotropins (LH and FSH) in proper quantities and ratios to induce ovulation. 
  • Precocious puberty: the onset of puberty with the development of external sexual characteristics before 8 years of age. Precocious puberty may result from the early activation of the HPO axis or excess secretion of sex steroids from the ovaries Ovaries Ovaries are the paired gonads of the female reproductive system that contain haploid gametes known as oocytes. The ovaries are located intraperitoneally in the pelvis, just posterior to the broad ligament, and are connected to the pelvic sidewall and to the uterus by ligaments. These organs function to secrete hormones (estrogen and progesterone) and to produce the female germ cells (oocytes). Ovaries or when obtained from exogenous sources.
  • Delayed puberty: the lack of testicular enlargement in boys by 14 years of age, and the lack of breast development in girls by 13 years of age. The etiology of delayed puberty Delayed Puberty Delayed puberty (DP) is defined as the lack of testicular growth in boys past the age of 14 and the lack of thelarche in girls past the age of 13. Delayed puberty affects up to 5% of healthy boys and girls, and half of all cases are due to constitutional growth delay. Delayed Puberty varies and is generally classified as central or gonadal. Approximately 2.5% of healthy children experience delayed puberty Delayed Puberty Delayed puberty (DP) is defined as the lack of testicular growth in boys past the age of 14 and the lack of thelarche in girls past the age of 13. Delayed puberty affects up to 5% of healthy boys and girls, and half of all cases are due to constitutional growth delay. Delayed Puberty.

References

  1. Herman-Giddens M., et al. (1997). Secondary sexual characteristics and menses in young girls seen in office practice: A study from the Pediatric Research in Office Settings Network. Pediatrics. https://pubmed.ncbi.nlm.nih.gov/9093289/
  2. Tanner, J.M., Davies, P.S. (1985). Clinical longitudinal standards for height and height velocity for North American children. The Journal of Pediatrics. https://pubmed.ncbi.nlm.nih.gov/3875704/
  3. Karpati, A.M., Rubin, C.H., Kieszak, S.M., Marcus, M., Troiano, R.P. (2002). Stature and pubertal stage assessment in American boys: The 1988-1994 Third National Health and Nutrition Examination Survey. The Journal of Adolescent Health. https://pubmed.ncbi.nlm.nih.gov/11869928/ 
  4. Cutler, G.B. Jr, Loriaux, D.L. (1980). Andrenarche and its relationship to the onset of puberty. Federation proceedings. https://pubmed.ncbi.nlm.nih.gov/6445284/

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