Pituitary Gland Disorders

Pituitary Essentials - Gland of Glory

• Location: Sella turcica of sphenoid bone.
• Lobes & Origin:
  • Anterior (Adenohypophysis): Ectoderm (Rathke's pouch).
  • Posterior (Neurohypophysis): Neuroectoderm (diencephalon downgrowth).
• Key Hormones:
  • Anterior: GH, PRL, ACTH, TSH, FSH, LH. (📌 FLAT PiG)
  • Posterior: ADH (vasopressin), Oxytocin (produced in hypothalamus, stored here).
• Blood Supply: Hypophyseal portal system (anterior); direct arterial (posterior).

⭐ The anterior pituitary is functionally linked to the hypothalamus by the hypophyseal portal system, crucial for hormone regulation.

Anterior Pituitary Overdrive - Hyperhormone Havoc

• Primarily due to functional pituitary adenomas; classified by hormone produced. Microadenoma <10 mm, Macroadenoma ≥10 mm.
• Prolactinoma (Most Common):
  • Symptoms: Galactorrhea, amenorrhea, infertility (females); ↓libido, impotence (males).
  • Dx: ↑Serum prolactin (>200 ng/mL highly suggestive).
  • Rx: Dopamine agonists (e.g., cabergoline).
• Somatotroph Adenoma (GH):
  • Gigantism (children); Acromegaly (adults: coarse features, large hands/feet, prognathism).
  • Dx: ↑GH, ↑IGF-1; no GH suppression with Oral Glucose Tolerance Test (OGTT).
  • Rx: Transsphenoidal surgery, somatostatin analogs (octreotide).
• Corticotroph Adenoma (ACTH) - Cushing's Disease:
  • Features: Central obesity, moon facies, purple striae, HTN, hyperglycemia.
  • Dx: ↑Cortisol, ↑ACTH; suppression with high-dose dexamethasone test.
  • Rx: Transsphenoidal surgery.

⭐ Prolactinomas are the most common type of hormone-secreting pituitary adenoma.

Anterior Pituitary Shutdown - Hormone Lowdown

• Causes (Panhypopituitarism):
  • Pituitary adenoma (esp. non-functioning), craniopharyngioma.
  • Sheehan's syndrome (postpartum necrosis after hemorrhage).
  • Pituitary apoplexy (sudden hemorrhage/infarction).
  • Iatrogenic (surgery, radiation).
  • Infiltrative (sarcoidosis, hemochromatosis), trauma.
• Hormone Deficiencies & Key Manifestations:
  • GH ↓: Dwarfism (children); Adults: ↓muscle mass, ↑fat, ↓QoL.
  • LH/FSH ↓: Hypogonadism (↓libido, infertility; amenorrhea, testicular atrophy).
  • TSH ↓: Secondary hypothyroidism (fatigue, cold intolerance, constipation).
  • ACTH ↓: Secondary adrenal insufficiency (weakness, hypotension, pallor). No hyperpigmentation. Aldosterone normal.
  • PRL ↓: Failure of postpartum lactation.

  ⭐ Sheehan's syndrome: Postpartum pituitary necrosis after obstetric hemorrhage. Presents with failure to lactate and amenorrhea.

Posterior Pituitary & Mass - Back & Bulk Issues

• Posterior Pituitary Disorders:

  • Diabetes Insipidus (DI): ↓ADH effect → polyuria, polydipsia, hyperNa+, dilute urine (SG < 1.005, UOsm < 200 mOsm/kg).
    • Central DI: ↓ADH secretion. Rx: Desmopressin.
    • Nephrogenic DI: Kidneys unresponsive to ADH. Rx: Thiazides.
  • SIADH: ↑ADH → euvolemic hyponatremia, conc. urine (UOsm > 100 mOsm/kg, UNa > 40 mEq/L). Rx: Fluid restriction.
    • 📌 SIADH: Serum Osm ↓, Urine Osm ↑, Hyponatremia.

• Mass Effects (e.g., Non-functioning adenoma):

  • Headache.
  • Visual: Bitemporal hemianopia (optic chiasm compression).
  • Hypopituitarism (compression).
  • Pituitary Apoplexy: Sudden bleed → severe headache, vision loss, ↓LOC. Emergency!

⭐ Bitemporal hemianopia is the commonest visual defect from a pituitary mass compressing the optic chiasm.

High‑Yield Points - ⚡ Biggest Takeaways

• Prolactinoma: Most common pituitary adenoma; causes galactorrhea, amenorrhea.
• GH adenoma: Gigantism (children), acromegaly (adults); ↑IGF-1 levels.
• ACTH adenoma: Leads to Cushing's disease (hypercortisolism, central obesity).
• Craniopharyngioma: Suprasellar tumor from Rathke's pouch; often calcified, visual field defects.
• Sheehan's syndrome: Postpartum pituitary necrosis due to obstetric hemorrhage and hypotension.
• Central Diabetes Insipidus: ADH deficiency causing polyuria, polydipsia, dilute urine.
• Empty Sella Syndrome: Often an incidental finding; herniation of arachnoid into sella turcica.