Puberty

Puberty

• Is the process of reproductive and sexual development and maturation that changes a child into an adult.

• During childhood, the HPO axis is suppressed and levels of GnRH, FSH and LH are very low.RR

• From the age of 8–9 years GnRH is secreted in pulsations of increasing amplitude and frequency.

• These are initially sleep-related, but as puberty progresses, these extend throughout the day. This stimulates secretion of FSH and LH by the pituitary glands, which in turn triggers follicular growth and steroidogenesis in the ovary.

• The oestrogen produced by the ovary then initiates the physical changes of puberty. The exact mechanism of onset of puberty is still unknown, but it is influenced by many factors including race, heredity, body weight and exercise.

• Leptin plays a permissive role in the onset of puberty.

Physical Changes in Puberty

1. breast development (thelache), first physical signs of puberty are breast budding 2–3 years before menarche
2. pubic (adrenarche), dependent on the secretion of adrenal androgens and is usually after thelarche
3. axillary hair growth
4. growth spurt (growth hormone secretion +GRH & androgens)
5. onset of menstruation (menarche).

• Leptin (metabolic hormones produced by adipose tissue in response to fat deposition) plays a role in puberty.
• The mean age of menarche is 12.8 years.
• Initial cycles are usually anovulatory and can be irregular (may take over 3 years to be regular).
• Pubertal development was described by Tanner, and the stages of breast and pubic hair development are often referred to as Tanner stages 1–5.
• The absence of menstruation is called amenorrhoea and may be primary or secondary.

Tanner Stages

Breast Development

1. Prepubertal
2. Breast and papilla are elevated as a small mound. Areolar diameter increases.
3. Further enlargement of the breast bud with loss of the contour separation between breast and areola.
4. Areola and papilla form a secondary mound.
5. Mature areola is part of the general breast contour.

Pubic Hair Development

1. Prepubertal
2. Sparse, lightly pigmented, chiefly along the medial border of the labia majora.
3. Darker, beginning to curl, increased amount spreading over the mons.
4. Increased amount of coarse, curly but limited to the mons.
5. Adult feminine triangle with spread to the medial surface of the thighs.

Puberty Disorders

Precocious Puberty

Onset of puberty before the age of 8 in a girl or 9 in a boy. It is classified as either central or peripheral.

1. Central Precocious Puberty (True Precocious)

Gonadotrophin dependent. The aetiology is often unknown (75% idiopathic), up to 25% are due to central nervous system (CNS) malformations or brain tumours.

2. Peripheral Precocious Puberty (Pseudopuberty)

Gonadotrophin independent, is always pathological and can be caused by

oestrogen secretion:

• ✓ Exogenous oestrogen ingestion.
• ✓ Hormone-producing tumour.
• ✓ McCune Albright syndrome.

McCune-Albright Syndrome

• Polystostotic fibrous dysplasia.
• Café au lait skin lesions.
• Precocious puberty. McCune-Albright syndrome involves the GNAS gene at locus 20q13 (p, q). More information: genetics4medics.com/mccune-albright-syndrome.html

Investigations and Treatment

Investigations

• ✓ Serum gonadotrophin (elevated in central and low in peripheral).
• ✓ Brain images.
• ✓ Pelvic US.

Treatment

• ✓ GNRH analoge.
• ✓ Surgery.

Delayed Puberty

When there are no signs of secondary sexual characteristics by the age of 14 years.

Causes

• Central defect (hypogonadotropic hypogonadism).
• Failure of gonadal function (hypergonadotropic hypogonadism).

Hypogonadotropic Hypogonadism (Central)

Gonadotrophins are:

• Constitutional.
• Anorexia nervosa.
• Excessive exercise.
• Chronic illness (diabetes or renal failure).
• Pituitary tumour.
• Kallman’s syndrome.

Associated with delayed puberty and primary amenorrhoea.

Hypergonadotropic Hypogonadism (Gonadal Failure)

Gonadotrophins are: The gonad does not function.

Causes:

• Turner syndrome.- XO
• XX gonadal dysgenesis.
• Premature ovarian failure at any age (including prior to pubertal age):
  • Idiopathic.
  • Autoimmune.
  • Metabolic disorder.
  • Following chemo- or radiotherapy for childhood cancer.

Associated with delayed puberty and primary amenorrhoea.

Hypergonadotropic hypogonadism can also occur later in life and will cause secondary amenorrhoea after normal sexual development.