A 29-year-old woman who delivered her first child 18 months ago has failed lactation since delivery, with amenorrhoea and cold intolerance. MRI shows a partially empty sella. The mechanism of her pituitary lesion is:

• A Autoimmune lymphocytic destruction of the anterior pituitary
• B Ischaemic necrosis of the hyperplastic pregnant pituitary after obstetric haemorrhage ✓
• C Apoplexy within a pre-existing prolactin-secreting macroadenoma
• D Granulomatous infiltration by sarcoidosis

Explanation

Sheehan syndrome is postpartum pituitary necrosis. During pregnancy the anterior pituitary enlarges physiologically with lactotroph hyperplasia outstripping its blood supply, making it vulnerable to infarction when major obstetric haemorrhage causes hypovolaemic shock. Failure of lactation is the earliest sign, followed by loss of other trophic hormones. Lymphocytic hypophysitis also occurs postpartum but is inflammatory rather than ischaemic, and apoplexy implies a pre-existing adenoma.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.