Hypopituitarism (Panhypopituitarism, Sheehan Syndrome)

Why Sheehan postpartum necrosis is correct

• Postpartum pituitary necrosis follows severe peripartum hemorrhage and hypotension, which infarcts the enlarged, metabolically demanding pregnancy gland.
• The picture is classic central (secondary) panhypopituitarism: failure to lactate is the earliest, most specific sign, followed by failure to resume menses and insidious fatigue.
• The labs confirm a central pattern: low free T4 with an inappropriately normal/low TSH, low cortisol, and low gonadotropins with low estradiol — multiple trophic hormones are low, pointing to pituitary failure rather than a single end-organ.
• Hyponatremia reflects glucocorticoid deficiency, and the absence of hyperpigmentation and hyperkalemia argues against a primary adrenal process.

Why the others are wrong

• Hereditary hemochromatosis — iron deposition can cause hypopituitarism, but it presents with elevated ferritin/transferrin saturation and features such as arthropathy, diabetes, and hepatic disease, not an acute postpartum-hemorrhage trigger with failure to lactate.
• Severe primary hypothyroidism — would show an ELEVATED TSH with low free T4, not the low/inappropriately normal TSH in this patient, and does not produce combined cortisol and gonadotropin deficiency.
• Primary adrenal insufficiency — Addison disease causes hyperpigmentation, hyperkalemia, and an ELEVATED ACTH; she has neither hyperpigmentation nor hyperkalemia (potassium 4.2 mEq/L), and it would not explain the simultaneous central hypothyroidism and hypogonadism seen here.
• Lymphocytic hypophysitis — autoimmune hypophysitis is the other classic cause of hypopituitarism in late pregnancy and the postpartum period, but it is not triggered by hemorrhage and typically presents with headache, frequently with visual disturbance, from an enlarged gland, and ACTH deficiency is often the earliest loss; severe peripartum hemorrhage with hypotension followed by inability to breastfeed and failure to resume menses points to ischemic necrosis.

Why Apoplexy of a pituitary adenoma is correct

• Pituitary apoplexy is hemorrhagic infarction of the pituitary, almost always within an adenoma and in most patients an adenoma that had never been diagnosed, and it announces itself exactly this way: thunderclap retro-orbital or frontal headache, vomiting, depressed consciousness, and a cranial neuropathy, with the third nerve hit most often because it runs in the lateral wall of the cavernous sinus next to the sella.
• The year of fatigue, low libido, and reduced shaving is the footprint of a macroadenoma that had been compressing the normal gonadotrophs, so the gland was already abnormal before the acute event.
• Loss of both temporal fields localizes the lesion to the optic chiasm, which sits directly above the sella; an expanding sellar mass compresses the decussating nasal retinal fibers.
• Fluid-unresponsive hypotension, hyponatremia, and hypoglycemia are acute ACTH deficiency from destruction of the corticotrophs. That triad is what converts a headache into an endocrine emergency and is the reason empiric stress-dose IV hydrocortisone is given immediately, after a random cortisol is drawn but without waiting for the result.
• A scan showing no subarachnoid blood does not argue against this diagnosis. Non-contrast CT demonstrates hemorrhage within the sella in only about 21 to 28 percent of apoplexy cases, and a study obtained to exclude subarachnoid hemorrhage is frequently reported on the subarachnoid spaces and ventricles without any comment on the sellar contents, so the sellar mass is easy to miss even when it is large enough to lift the chiasm. Urgent dedicated sellar MRI is the confirmatory study, and lumbar puncture is nondiagnostic here and only delays the glucocorticoid these patients need.

Why the others are wrong

• Aneurysmal subarachnoid hemorrhage - a ruptured posterior communicating artery aneurysm is the right first thought for thunderclap headache with a painful third-nerve palsy, but non-contrast CT is roughly 95 percent or better for aneurysmal blood through the first 24 hours, so a clean subarachnoid space on a scan done at 10 hours makes it unlikely, and it would still explain neither the bitemporal field cut nor the fluid-refractory hypotension with hyponatremia and hypoglycemia (the trap is stopping at the thunderclap headache and reaching for a lumbar puncture).
• Adrenal crisis in Addison disease - the shock that does not answer 2 L of saline, the sodium of 126, and the glucose of 58 genuinely are an adrenal crisis, but primary adrenal failure cannot produce a headache that peaks in seconds, a third-nerve palsy, or bitemporal field loss, and destruction of the whole cortex also costs aldosterone, so hyperkalemia, hyperpigmentation, and salt craving would be expected (the trap is stopping at the crisis and never asking why the eye and the visual fields are involved).
• Cavernous sinus venous thrombosis - painful ophthalmoplegia involving the third nerve fits, but it evolves over days out of a facial, dental, or sinus infection and brings proptosis, chemosis, and periorbital edema, usually with fever and with V1 to V2 sensory loss or a sixth-nerve palsy; it spares the chiasm and does not cause adrenal crisis.
• Suprasellar craniopharyngioma - a craniopharyngioma can compress the chiasm and the pituitary to cause bitemporal field loss and slowly progressive hypopituitarism like his year of fatigue and low libido, but it grows over months to years and does not typically produce a headache that peaks in seconds, an acute pupil-involving third-nerve palsy, or a sudden adrenal crisis (the trap is explaining the chronic picture and missing the acute event).

Additional high-yield points

• Classic precipitants: anticoagulation or antiplatelet therapy, major surgery and cardiopulmonary bypass, hypertensive surges, head trauma, pituitary dynamic testing, starting or stopping a dopamine agonist, and pregnancy. Sheehan syndrome is the postpartum ischemic analogue occurring in a normal, non-adenomatous gland.
• Give hydrocortisone 100 mg IV followed by 50 mg every 6 hours (or a continuous infusion) plus isotonic fluids; hold levothyroxine until glucocorticoid is on board, because thyroid hormone first can precipitate adrenal crisis.
• Emergency transsphenoidal decompression is reserved for severely reduced visual acuity, severe or deteriorating visual field defects, or a declining level of consciousness; an isolated ocular palsy without visual involvement is not by itself an indication, because ophthalmoplegia resolves with glucocorticoids and supportive care in most patients.
• The hyponatremia here is cortisol deficiency plus SIADH, not mineralocorticoid loss: aldosterone is renin-angiotensin driven and is preserved in secondary adrenal insufficiency, so hyperkalemia is typically absent, unlike primary (Addison) disease.
• Fever with meningismus would move bacterial meningitis to the front of this differential, and a stiff neck with a scan free of blood is the classic trigger for lumbar puncture; this man is afebrile with no meningismus, so tapping him only postpones the steroid he needs.
• Send a full anterior pituitary panel at presentation (cortisol, ACTH, free T4, TSH, LH, FSH, testosterone or estradiol, IGF-1, prolactin) and watch for delayed diabetes insipidus, which is uncommon because the posterior lobe is usually spared.