A 24-year-old woman delivers vaginally after a delivery complicated by massive postpartum hemorrhage and hypotension requiring transfusion. Postpartum she fails to lactate despite regular suckling, then develops fatigue, pallor and loss of pubic hair. Serum prolactin is undetectable and cortisol response to hypoglycemia is blunted. Which mechanism explains her failure to lactate specifically?

• A Ischemic necrosis of pituitary lactotrophs, which enlarge greatly during pregnancy and have high metabolic demand ✓
• B Damage to the supraoptic nucleus preventing oxytocin release during feeding
• C Elevated dopamine tone from hypothalamic injury suppressing residual lactotrophs
• D Infarction of the posterior pituitary interrupting the portal venous drainage

Explanation

Sheehan syndrome arises when peripartum hemorrhage causes ischemic necrosis of the enlarged pituitary. Lactotrophs undergo marked hypertrophy and hyperplasia during pregnancy and are typically the earliest and most severely affected cells, so failure of lactation is often the presenting feature, followed later by gonadotropin, TSH and ACTH deficiency. Oxytocin deficiency impairs let-down but milk synthesis depends on prolactin, and the posterior pituitary has independent arterial supply, sparing it early.

Reference: Williams Obstetrics, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.