Pituitary Disorders

Pituitary Anatomy & Hormones - Gland Central

• Anatomy: Sella turcica. Lobes:
  • Anterior (Adenohypophysis): Rathke's pouch origin.
  • Posterior (Neurohypophysis): Neural ectoderm.
• Hypothalamic Control: Via infundibulum.
  • Anterior: Portal system (releasing/inhibiting hormones).
  • Posterior: Neural; stores ADH (supraoptic), Oxytocin (paraventricular) made in hypothalamus.
• Hormones (Anterior): GH, PRL, ACTH, TSH, FSH, LH. 📌 (FLAT PEG)

⭐ Craniopharyngioma, from Rathke's pouch remnants, is a common pediatric suprasellar tumor causing visual field defects.

Growth Hormone Disorders - Ups & Downs

Growth Hormone (GH) from anterior pituitary, regulated by GHRH & Somatostatin, is vital for linear growth via IGF-1. Imbalances lead to significant disorders.

GH Deficiency (GHD) vs. GH Excess

⭐ Laron Syndrome: GH receptor defect → GH insensitivity. Features: Dwarfism, high GH, low IGF-1. Autosomal Recessive.

📌 Mnemonic for common GH stimulation tests: "CLAG" (Clonidine, L-DOPA, Arginine, Glucagon/Insulin).

Other Anterior Pituitary Issues - Command Crisis

• Panhypopituitarism: Deficiency of ≥1 anterior pituitary hormones.
  • Causes: Tumors (craniopharyngioma), Sheehan's syndrome, trauma, radiation, infiltrative disease.
  • 📌 Hormone loss sequence: GH → LH/FSH → TSH → ACTH (Mnemonic: "Go Look For The Adenoma").
  • Dx: Low basal hormones, dynamic stimulation tests (e.g., Insulin Tolerance Test). Rx: Hormone replacement.
• Cushing's Disease: ACTH-secreting pituitary adenoma → ↑cortisol.
  • Features: Central obesity, moon facies, purple striae, hypertension, glucose intolerance.
  • Dx: ↑24h UFC, no suppression on LDDST (Low-Dose Dexamethasone Suppression Test), suppression on HDDST (High-Dose Dexamethasone Suppression Test), ↑ACTH.
  • Rx: Transsphenoidal surgery.

⭐ Nelson's Syndrome: Pituitary adenoma growth, ↑ACTH & hyperpigmentation post-bilateral adrenalectomy for Cushing's disease treatment.

Posterior Pituitary Disorders - Water Works

• Diabetes Insipidus (DI): "Dry Inside" - ↓ADH action.
  • Symptoms: Polyuria (often > 3L/day), polydipsia, dilute urine (Osm < 200 mOsm/kg, SG < 1.005), potential hypernatremia.
  • Central DI: ↓ADH secretion. Dx: Water deprivation test followed by Desmopressin (Urine Osm ↑ by >50%). Tx: Desmopressin.
  • Nephrogenic DI: Kidney unresponsive to ADH. Dx: No/minimal Urine Osm response to Desmopressin. Tx: Thiazides, Amiloride.
• SIADH (Syndrome of Inappropriate ADH): "Soaked Inside" - Excessive ADH effect. 📌 Soaked Inside.
  • Symptoms: Euvolemic hyponatremia (Na+ < 135 mEq/L), inappropriately concentrated urine (Osm > 100 mOsm/kg & often > serum Osm), ↓serum Osm (< 275 mOsm/kg).
  • Tx: Fluid restriction, demeclocycline, vaptans. Correct Na+ slowly.

⭐ In SIADH, urine sodium is typically elevated (e.g., > 40 mEq/L) despite hyponatremia, reflecting euvolemic or slightly hypervolemic state with ongoing natriuresis.

High‑Yield Points - ⚡ Biggest Takeaways

• Craniopharyngioma: Most common pediatric suprasellar tumor; causes growth failure, bitemporal hemianopia.
• GH Deficiency: Presents as short stature, delayed bone age; GH stimulation tests are diagnostic.
• Central Diabetes Insipidus: Features polyuria, polydipsia, hypernatremia; use water deprivation test.
• SIADH: Causes euvolemic/hypervolemic hyponatremia and concentrated urine.
• Cushing's Disease: Leads to growth failure, central obesity, hypertension from pituitary ACTH.
• Congenital Hypopituitarism: Neonatal signs include hypoglycemia, micropenis, prolonged jaundice.