Pituitary and Adrenal Disorders
Pituitary disease
Pituitary evaluation requires understanding the hormone axis: low target-hormone levels with low or inappropriately normal pituitary hormones suggest central deficiency. Prolactinomas cause galactorrhea, amenorrhea, or hypogonadism; prolactin >200 ng/mL strongly suggests a macroadenoma, while mild elevations can reflect stalk effect or medications. Acromegaly is screened with IGF-1 and confirmed by failure of GH suppression during an oral glucose tolerance test. Pituitary apoplexy presents with sudden headache, visual field loss, ophthalmoplegia, and hypotension; give glucocorticoids urgently and obtain imaging.
Adrenal disease
Primary adrenal insufficiency causes low cortisol, high ACTH, hyperpigmentation, hyperkalemia, and hyponatremia; secondary insufficiency has low ACTH and normal aldosterone. Draw cortisol and ACTH before giving dexamethasone in suspected adrenal crisis, then treat empirically. Cosyntropin stimulation can be normal in acute secondary insufficiency because the adrenal glands have not yet atrophied. Cushing syndrome is screened with late-night salivary cortisol, 24-hour urine free cortisol, or a 1-mg overnight dexamethasone suppression test. Primary hyperaldosteronism is screened with an aldosterone-to-renin ratio; confirm before adrenal vein sampling. Pheochromocytoma is screened with plasma free metanephrines, and alpha-blockade precedes beta-blockade.
Trap and worked example
A 62-year-old with euvolemic hyponatremia, urine osmolality 520 mOsm/kg, and low uric acid has SIADH after hypothyroidism and adrenal insufficiency are excluded. Rule of thumb: in suspected adrenal crisis, do not delay steroids for confirmatory testing.