Hypopituitarism

Deficiency of one or more pituitary hormones. See also Pituitary tumour / apoplexy for the mass/hypersecretion and apoplexy picture.

Anterior pituitary: ACTH, TSH, growth hormone, prolactin, FSH, LH. Posterior pituitary: arginine vasopressin (ADH) and oxytocin.

Causes

• Pituitary adenoma (commonest in adults)
• Prior cranial radiotherapy (often years later)
• Head injury; subarachnoid haemorrhage; major postpartum haemorrhage (Sheehan syndrome)
• Genetic causes (usually detected in childhood); childhood surgery/radiotherapy

Clinical features

Adults: amenorrhoea, sexual dysfunction, fatigue, depression, altered mental state, cold intolerance, postural light-headedness. Signs: marked pallor, loss of body hair, fine facial wrinkling, delayed reflexes, testicular atrophy, orthostatic hypotension.

Children: hypoglycaemia (combined ACTH + GH deficiency), prolonged neonatal jaundice (giant-cell hepatitis), micropenis, undescended testes, growth failure, delayed puberty.

Biochemistry: low T4 without an elevated TSH; low oestrogen/androgen without elevated LH/FSH (i.e. inappropriately non-elevated trophic hormones).

Management

Acute hypopituitarism — precipitated by intercurrent illness, infection or trauma, or from head injury, Sheehan syndrome, or pituitary apoplexy. Presents with altered mental state, orthostatic hypotension, fever, hyponatraemia and hypoglycaemia.

• Measure glucose and electrolytes before treatment, but for severe signs start glucocorticoid replacement without waiting for results: IV hydrocortisone (adults; IV/IM in children), switching to oral when tolerated.
• IV normal saline; correct hypoglycaemia.

Chronic hypopituitarism — specialist-managed replacement of deficient axes. Glucocorticoid and thyroid hormone replacement are usually lifelong; gonadal replacement indefinitely in men and to ~age 50 in women; growth hormone and vasopressin replacement individualised. A woman who is pregnant or planning pregnancy needs endocrine-led antenatal care with serial fetal-growth ultrasound.