A woman develops failure of lactation after a delivery complicated by massive postpartum haemorrhage requiring transfusion. Subsequent evaluation shows low cortisol, low TSH, low LH and FSH, but normal ADH function. The reason the anterior pituitary is selectively vulnerable in this condition is:

• A Pregnancy-specific antibodies occlude the superior hypophyseal arteries
• B Anterior pituitary cells have the highest metabolic rate of any endocrine tissue and cannot survive hypoxia
• C The posterior pituitary receives blood from the same portal vessels but has lower oxygen demand
• D The anterior pituitary lacks direct arterial supply and depends entirely on the low-pressure hypophyseal portal system ✓

Explanation

Sheehan syndrome is ischemic necrosis of the anterior pituitary after obstetric haemorrhage. The adenohypophysis has no direct arterial inflow and depends on the long portal veins carrying blood from the median eminence, making it vulnerable to the fall in perfusion pressure during shock. The posterior pituitary is spared because it is supplied directly by the inferior hypophyseal artery, which explains preserved ADH function and kills option C.

Reference: Williams Textbook of Endocrinology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.