Neuroendocrine Disorders and Reproduction

HPO Axis Regulation - Brainy Ovary Chat

• Hypothalamus: Secretes GnRH in critical pulses; Kisspeptin is a key modulator.
• Anterior Pituitary: GnRH stimulates gonadotrophs to release FSH and LH.
• Ovary:
  • FSH: Drives follicular maturation; granulosa cells produce estrogen & inhibin.
  • LH: Theca cells (androgens); mid-cycle surge → ovulation; corpus luteum → progesterone.
• Feedback Control:
  • Negative: Estrogen, progesterone, inhibin (↓FSH) suppress hypothalamus & pituitary.
  • Positive: Sustained high estrogen (mid-cycle) induces pituitary LH surge → ovulation.
• Flowchart:

• Exam Highlight:

  ⭐ Pulsatile GnRH is essential. Continuous GnRH (agonists) causes pituitary desensitization, ↓FSH/LH. Used for endometriosis, fibroids, precocious puberty.

Hypothalamic Disorders - Stress & Scent Woes

• Functional Hypothalamic Amenorrhea (FHA): Reversible ↓GnRH pulsatility.
  • Causes: Stress (psychological, intense exercise), nutritional deficits (low body weight, eating disorders).
  • Pathophysiology: ↓GnRH pulsatility → ↓LH, ↓FSH → ↓$E_2$ → anovulation, amenorrhea.
  • Diagnosis: Low/normal FSH & LH, low $E_2$. Negative progestin challenge (no withdrawal bleed).
  • Management: Address underlying cause, HRT for bone protection if prolonged.
• Kallmann Syndrome: Genetic disorder; failed migration of GnRH & olfactory neurons.
  • Features: Hypogonadotropic hypogonadism (delayed/absent puberty) + Anosmia or Hyposmia.
  • 📌 Mnemonic: KALlmann = Kills Aroma (anosmia) & Lowers Life (gonads).
  • Diagnosis: ↓FSH, ↓LH, ↓sex steroids; MRI (olfactory bulb aplasia/hypoplasia).
  • Management: Pulsatile GnRH for fertility; HRT for secondary sexual characteristics.

⭐ Kallmann Syndrome: congenital GnRH deficiency with anosmia/hyposmia, often X-linked (KAL1 gene).

Pituitary Gland Disorders - Gland Gone Wild

• Hyperprolactinemia: Prolactin >25 ng/mL. Commonest pituitary hyperfunction.
  • Causes: Prolactinoma (PRL often >200 ng/mL), drugs (antipsychotics, metoclopramide), hypothyroidism, stalk compression.
  • Sx: Galactorrhea, amenorrhea, infertility.
  • Rx: Dopamine agonists (cabergoline, bromocriptine). Pituitary MRI for diagnosis.

  ⭐ Prolactinomas are the most common hormone-secreting pituitary adenomas.

• Sheehan's Syndrome: Postpartum pituitary necrosis from severe obstetric hemorrhage.
  • Leads to panhypopituitarism.
  • Sx: Agalactia (earliest), amenorrhea, fatigue.
  • Rx: Hormone replacement therapy.

• Pituitary Apoplexy: Sudden hemorrhage into a pituitary adenoma.
  • Sx: Severe headache, visual loss, ophthalmoplegia. ⚠️ Neurological emergency!
  • Rx: Steroids, ?surgery.
• Empty Sella Syndrome: CSF fills sella. Often incidental; can cause hypopituitarism.

Systemic Influences & Dx - Hormone Harmony Hunt

• Systemic Disruptors:
  • Thyroid: ↑/↓ TSH → anovulation.
  • Adrenal: ↑ Cortisol/Androgens (Cushing's, CAH) → cycle disruption.
  • Pituitary: ↑ Prolactin (Prolactinoma) → amenorrhea, galactorrhea.
  • Metabolic: PCOS, obesity → insulin resistance.
  • Stress, eating disorders, chronic illness.
• Diagnostic "Hormone Hunt":
  • History & Exam (menstrual, virilization signs, galactorrhea).
  • Labs:
    • Initial: FSH, LH, Estradiol, Prolactin, TSH.
    • Specific: Testosterone, DHEAS, 17-OHP.
  • Imaging: Pelvic USG, Pituitary MRI (if indicated).
  • 📌 Prolactin, Androgens, Thyroid, HPO axis - PATH to Dx.

⭐ Prolactin levels > 100 ng/mL strongly suggest prolactinoma; levels 20-100 ng/mL can be due to drugs, stress, or pituitary stalk compression (non-pathological hyperprolactinemia).

High‑Yield Points - ⚡ Biggest Takeaways

• Hypothalamic amenorrhea: Due to stress, weight loss, or excessive exercise; results in low GnRH, FSH, LH, and estrogen.
• Kallmann syndrome: Features anosmia & hypogonadotropic hypogonadism from defective GnRH neuron migration.
• Sheehan's syndrome: Postpartum pituitary necrosis causing panhypopituitarism; lactation failure is a key early sign.
• Hyperprolactinemia: A common cause of amenorrhea & infertility; prolactin inhibits GnRH. Often due to prolactinomas or drugs (e.g., antipsychotics).
• PCOS: Neuroendocrine aspects include ↑LH/FSH ratio, androgen excess, and insulin resistance, disrupting ovulation.
• Empty Sella Syndrome: CSF fills sella turcica, potentially compressing the pituitary; may cause hypopituitarism or be asymptomatic.