Sheehan Syndrome
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Direct answer
Sheehan syndrome is ischaemic necrosis of the anterior pituitary after severe postpartum haemorrhage with hypotension, causing hypopituitarism. The pituitary enlarges in pregnancy and depends on a low-pressure portal supply, so shock injures the anterior lobe first. The earliest clinical clue is failure of lactation, followed by amenorrhoea, and management is lifelong replacement, beginning with hydrocortisone.
What you must remember
- Mechanism: the pituitary enlarges in pregnancy and is supplied by a low-pressure portal circulation, so hypotension during haemorrhage causes necrosis of the anterior lobe.
- Early sign: failure of lactation after delivery is the earliest and most typical clue to Sheehan syndrome.
- Menstrual failure: secondary amenorrhoea follows loss of gonadotrophin secretion, and pubic and axillary hair is often lost.
- Hormone pattern: low FSH and LH with low oestradiol, low TSH with low free thyroxine, low morning cortisol and low prolactin.
- Posterior pituitary: diabetes insipidus is uncommon because the posterior lobe is usually spared, so its presence argues against the diagnosis.
- Management: hydrocortisone first, then levothyroxine, then oestrogen and progestogen replacement where indicated, with fertility treated by specialist ovulation induction.
A stepwise diagnosis from failed lactation to replacement
A 28-year-old woman who had a severe postpartum haemorrhage with shock cannot breastfeed and has not had periods for six months. Her presentation suggests pituitary failure, and the diagnosis must be confirmed before treatment begins. Sheehan syndrome is still reported in India, where postpartum haemorrhage remains common and emergency care is uneven. The steps below show the usual sequence.
- Take the obstetric history: Look for massive postpartum haemorrhage, shock, transfusion or prolonged hypotension, which together form the setting for pituitary necrosis.
- Test the pituitary axes: Measure FSH, LH, oestradiol, prolactin, TSH with free thyroxine, morning cortisol and IGF-1 to define the pattern of hypopituitarism.
- Image the sella: MRI typically shows a small or empty sella with a reduced anterior pituitary, supporting but not replacing hormone testing.
- Replace cortisol first: Hydrocortisone is started before thyroxine, since thyroid replacement can precipitate adrenal crisis in a patient with untreated cortisol deficiency.
- Restore thyroid and sex steroids: Levothyroxine follows once cortisol cover is in place, and oestrogen with progestogen is given where the uterus is present, to restore secondary sexual characteristics and bone density.
- Plan fertility and follow-up: Ovulation induction is specialised care if pregnancy is wanted, and replacement and bone density are reviewed lifelong.
Where the exam tries to catch you
Examiners test whether you can recognise pituitary failure after delivery and order replacement safely.
- Trap: Start levothyroxine first because the thyroid picture looks obvious. Correct: Hydrocortisone must come first, because thyroid hormone increases cortisol turnover and can trigger adrenal crisis in untreated patients.
- Trap: Expect diabetes insipidus as a common feature. Correct: Posterior pituitary function is usually preserved in Sheehan syndrome, so diabetes insipidus argues against the diagnosis or suggests another cause.
- Trap: Attribute failed lactation to poor breastfeeding technique alone. Correct: Failed lactation after severe haemorrhage is a pituitary clue, and the other pituitary axes should be checked.
- Trap: Label every postpartum pituitary failure as Sheehan syndrome. Correct: Pituitary tumours, apoplexy and other causes must be excluded, and MRI with hormone testing helps separate them.
Frequently asked questions
What is the earliest clinical sign of Sheehan syndrome?
Failure of lactation after delivery is the earliest and most typical sign of Sheehan syndrome. It is followed by failure to resume menstruation, because gonadotrophin secretion from the anterior pituitary is lost after the haemorrhage.
Why is diabetes insipidus rare in Sheehan syndrome?
Diabetes insipidus is rare in Sheehan syndrome because the posterior pituitary receives its blood supply from the inferior hypophyseal artery, which is usually spared. The anterior lobe, supplied by the low-pressure portal system, is the part that necroses after haemorrhage.
Which hormone should be replaced first in Sheehan syndrome?
Hydrocortisone should be replaced first in Sheehan syndrome, before levothyroxine, to prevent precipitating an adrenal crisis. Once cortisol cover is in place, thyroid and sex steroid replacement follow according to the individual's needs.
Which laboratory pattern supports Sheehan syndrome?
Low FSH and LH with low oestradiol, low TSH with low free thyroxine and a low morning cortisol form the usual pattern in Sheehan syndrome. Low prolactin, together with failed lactation and a history of severe postpartum haemorrhage, supports the diagnosis.