AKT · Endocrine/Pituitary & ADHlow yield

Hypopituitarism

Deficiency of one or more anterior pituitary hormones (tumour, surgery, Sheehan, apoplexy)

Overview

Deficiency of one or more anterior pituitary hormones, from a pituitary/parasellar tumour (and its treatment), Sheehan syndrome (postpartum pituitary infarction), pituitary apoplexy, infiltration or trauma. Hormones are typically lost in the order GH → gonadotrophins → TSH → ACTH. The ACTH/cortisol deficiency is the dangerous one. Replace the deficient axes — glucocorticoid first.

Recognise

Tiredness, weight change, loss of libido/amenorrhoea (gonadotrophins), cold intolerance (TSH), pallor (no hyperpigmentation)
Sheehan: failure of lactation + amenorrhoea after a postpartum haemorrhage; apoplexy: sudden headache, visual loss, ophthalmoplegia
Secondary adrenal insufficiency (low cortisol, low/normal ACTH) — no hyperkalaemia (aldosterone preserved)

Red flags

Pituitary APOPLEXY (sudden severe headache, visual loss, ophthalmoplegia, hypotension) → emergency (steroids + neurosurgery)
Secondary adrenal crisis under stress → IV hydrocortisone

Differentials & how to tell them apart

Primary end-organ failuree.g. primary hypothyroidism (high TSH) or primary adrenal failure (high ACTH, hyperkalaemia) — pituitary causes have LOW/normal trophic hormones

Sheehan syndromepostpartum context with failed lactation

Non-functioning pituitary adenomamass effect + hypopituitarism ± mild prolactin rise

Investigations

Baseline pituitary panel: 9 am cortisol/ACTH, free T4/TSH, LH/FSH/testosterone/oestradiol, IGF-1/GH, prolactin; dynamic tests as needed. MRI pituitary; visual fields.

Management

Replace deficient axes — glucocorticoid first, then thyroxine/sex steroids/GH

1Assess all axes and image the pituitary. Replace the deficient hormones — give GLUCOCORTICOID before levothyroxine.Gate: Always replace cortisol BEFORE thyroxine (thyroxine first can precipitate an adrenal crisis); pituitary apoplexy is a neurosurgical emergency needing immediate steroids
2Lifelong replacement with stress dosing and a steroid card; treat the underlying cause (tumour); monitor axes.

Hydrocortisone (replace cortisol FIRST) — the priority axis — sick-day rules apply

Levothyroxine, sex steroids, GH — replace the other deficient axes (after glucocorticoid)

Key points

Low trophic hormone + low target hormone = secondary (pituitary) failure. Replace cortisol first. Failed lactation + amenorrhoea after a postpartum bleed = Sheehan; sudden headache + visual loss = apoplexy.

Monitor & prognosis

Hormone levels; stress dosing; tumour surveillance.

Good on replacement; apoplexy can threaten sight/life.

Source: Society for Endocrinology