Pituitary Disorders

Prolactinoma, acromegaly, SIADH, DI, Sheehan, hypopituitarism.

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◆Prolactinoma

•Most common functioning pituitary adenoma
•Women: amenorrhea + galactorrhea + infertility
•Men: ↓libido + ED + infertility; often present later when large (bitemporal hemianopsia)
•Rule out causes of secondary hyperprolactinemia: pregnancy, hypothyroidism (TRH stimulates prolactin), drugs (antipsychotics, metoclopramide, methyldopa, opioids), chronic kidney disease
•Treat: dopamine agonist (cabergoline or bromocriptine) shrinks tumor and ↓prolactin; surgery if refractory

•Excess GH from somatotroph adenoma
•Adults (closed growth plates): acromegaly — large hands/feet/jaw, frontal bossing, deepening voice, OSA, HTN, cardiomyopathy, DM, colon polyps
•Children (before closure): gigantism
•Screen: IGF-1 (single sample); confirm: GH not suppressed after oral glucose
•MRI pituitary
•Treat: transsphenoidal surgery; octreotide/lanreotide if persistent; cabergoline; pegvisomant

•Euvolemic hyponatremia + concentrated urine (osm >100, ofen >300) + ↑urine Na (>30) + normal/low BUN/Cr/uric acid
•Causes: CNS (stroke, tumor, infection), lung (small cell CA, pneumonia), drugs (SSRIs, carbamazepine, cyclophosphamide), surgery
•Treat: fluid restriction first; salt tabs; demeclocycline or vaptans (tolvaptan, conivaptan) for refractory
•Severe symptomatic (seizure): 3% hypertonic saline — correct <8–10 mEq/L per 24 hr

•Polyuria + polydipsia + dilute urine despite hypernatremia
•Central DI: ↓ ADH (head trauma, pituitary surgery, tumor, autoimmune)
•Nephrogenic DI: ADH-resistant kidney (lithium, hypercalcemia, hypokalemia, CKD)
•Water deprivation test: urine osm stays low; desmopressin challenge: central DI → urine osm rises >50%; nephrogenic → little response
•Treat: central → desmopressin; nephrogenic → low salt + thiazide (paradoxical) + amiloride; stop offending drugs

•Postpartum hemorrhage → pituitary infarction (hypertrophied during pregnancy)
•First sign: failure to lactate (prolactin)
•Other: amenorrhea, fatigue (TSH/cortisol deficiency), cold intolerance
•Treat: replace all deficient hormones (hydrocortisone FIRST, then levothyroxine)

◆Bitemporal hemianopsia + pituitary mass = compression of optic chiasm
◆Always treat cortisol deficiency BEFORE thyroid (giving thyroxine first can precipitate adrenal crisis)
◆Empty sella syndrome: enlarged sella with thin rim of pituitary; often asymptomatic
◆Acromegaly → screen for colonoscopy + sleep apnea

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