Acute Sheehan Syndrome Presenting with Hyponatremia

Introduction: Sheehan’s syndrome (SS) presents in months to years with lactation failure, amenorrhea, hypothyroidism and adrenal insufficiency. In cases of mild hypopituitarism, diagnosis can be delayed by decades. Acute manifestations of SS are unusual as well as hyponatremia as the initial manifestation. Case Description: A 39-year-old woman 35w5d gestation underwent C-section, hysterectomy and salpingectomy for placenta accreta. Course was complicated by hemorrhagic shock requiring massive transfusion of blood products and brief vasopressor support. A day after surgery she had mild hyponatremia of 134mmol/L. Serum sodium (sNa) ranged from 137-140. By post-op day 6 sNa was 120 despite fluid restriction and potassium was 5.7. She was asymptomatic, euvolemic with stable vital signs, no neurologic deficits but reports fatigue and reduced milk supply. Work-up showed low serum osmolality, elevated urine osmolality and low serum uric acid. SNa failed to improve (nadir 119) with salt tablets and furosemide. Suspecting SS, hydrocortisone and levothyroxine were started. Hormonal testing was suggestive of hypopituitarism. Pituitary MRI showed absent enhancement throughout majority of the gland centrally. 2 days later, sNa had normalized and she was discharged. 2 months later, sNa, prolactin and thyroxine were normal (on replacement). All other pituitary hormones were depressed, consistent with panhypopituitarism. She remains on hydrocortisone, levothyroxine and estrogen replacement 8 months after delivery. Discussion: SS's reported in 1%-3% of postpartum women in developed countries. It presents with chronic nonspecific symptoms over months to years. Acute SS is rare, with <30 cases reported and 17 with hyponatremia as initial presentation. The mechanism is thought to be from unsuppressed vasopressin release, decreasing free water excretion in absence of cortisol. This mimics SIADH clinically and biochemically. In setting of postpartum hemorrhage, SS should be suspected, especially with symptoms suggestive of hypopituitarism. Prompt evaluation and hormone replacement are crucial in preventing both short and long-term complications.