Panhypopituitarism

Sheehan syndrome is postpartum pituitary infarction after massive obstetric hemorrhage, causing panhypopituitarism with failure of lactation and deficiencies of glucocorticoids, thyroid hormone, and sex hormones. First-line treatment is glucocorticoid replacement started before thyroid hormone, followed by levothyroxine and, when indicated, sex hormone and growth hormone replacement.

Pituitary apoplexy is sudden hemorrhage or infarction of a pituitary adenoma causing severe headache, visual loss, ophthalmoplegia, and acute adrenocorticotropic hormone (ACTH) deficiency, and is a medical emergency. First-line treatment is immediate IV hydrocortisone given empirically before confirmatory testing when adrenal insufficiency is suspected, with urgent pituitary MRI and surgical decompression reserved for progressive visual loss.

Secondary adrenal insufficiency is ACTH deficiency from pituitary or hypothalamic disease, or most commonly from withdrawal of prolonged exogenous glucocorticoid therapy, causing isolated cortisol deficiency without hyperpigmentation or hyperkalemia because aldosterone secretion is preserved. Lifelong glucocorticoid replacement with hydrocortisone, with dose increases during illness, prevents adrenal crisis.

Adrenal crisis is life-threatening acute glucocorticoid deficiency, most often precipitated by infection or another physiologic stress in a patient with known or unrecognized adrenal insufficiency, presenting with dehydration, hypotension, or shock out of proportion to the concurrent illness. Treatment is immediate intravenous hydrocortisone 100 mg followed by 50 mg every 6 hours plus isotonic saline with dextrose, without waiting for confirmatory labs.

Hypothyroidism is thyroid hormone deficiency, most commonly caused by autoimmune (Hashimoto) thyroid failure in iodine-sufficient countries, diagnosed by an elevated thyroid-stimulating hormone with a low or normal free thyroxine. First-line treatment is levothyroxine dosed at 1.6 mcg/kg lean body weight orally once daily, titrated using thyroid-stimulating hormone rechecked no sooner than 6 weeks after any dose change.

Central diabetes insipidus is inability of the posterior pituitary to produce adequate antidiuretic hormone, causing free water loss, polyuria, and hypernatremia; common causes include pituitary/hypothalamic tumor, surgery, trauma, and infiltrative disease. Diagnosis is confirmed with a water deprivation test followed by a desmopressin challenge, and treatment is desmopressin (DDAVP) 10-40 mcg intranasally or 0.1-0.4 mg orally, dosed once nightly or twice daily and titrated to control polyuria while avoiding dilutional hyponatremia from over-replacement.

A nonfunctioning pituitary adenoma is a benign pituitary tumor, usually of gonadotroph origin, that does not secrete a clinically excessive hormone and presents through mass effect (visual field loss, headache) or hypopituitarism rather than a hypersecretory syndrome. Diagnosis requires excluding hormone excess and screening for hypopituitarism; treatment is observation for a small asymptomatic incidentaloma or transsphenoidal surgery for mass effect, apoplexy, or growth on follow-up.

Growth hormone (GH) deficiency causes short stature in children and a nonspecific syndrome of fatigue, reduced muscle mass, and adverse body composition in adults, usually from hypothalamic-pituitary disease, surgery, irradiation, or head trauma. Diagnosis relies on a low age-adjusted IGF-1 with confirmatory provocative testing when needed, and treatment is daily subcutaneous somatropin titrated to a normal IGF-1, avoided in active malignancy or an untreated pituitary tumor.