MON-611 - Resolution of Estrogen-Mediated Hypoglycemia Following Oophorectomy in A Post-Bariatric Surgery Patient with Insulin Autoantibodies

Background
Post-bariatric surgery hypoglycemia usually presents as postprandial hypoglycemia within 1-5 years of surgery. Atypical features including late onset hypoglycemia, cyclical patterns, or rare lab findings should prompt evaluation for alternative etiologies. Insulin autoimmune syndrome (IAS) is a rare cause of hypoglycemia characterized by insulin autoantibodies and may be hormonally modulated.

Case Presentation
A 45-year-old woman with prior biliopancreatic diversion with duodenal switch in 2007 presented with symptomatic hypoglycemia beginning in 2022, including syncope. Although she endorsed daily hypoglycemia that fulfilled Whipple’s triad, she noted that the symptoms worsened cyclically, approximately every two weeks. She had no history of prediabetes, diabetes or use of hypoglycemic medications.

Due to family circumstances, she was unable to undergo a 72-hour fast to obtain a hypoglycemic critical sample. However, continuous glucose monitor (CGM) with fingerstick calibrations showed hypoglycemia 50% of the time, with 22% being severe hypoglycemia. As part of the non-hypoglycemia-dependent evaluation, insulin autoantibodies were measured and found to be markedly elevated at 12.3 U/mL (RR < 0.4 U/mL).

Review of systems revealed a complex gynecologic history, including endometrial ablation resulting in amenorrhea. Estradiol levels were monitored to assess for perimenopause. However, estradiol was markedly elevated at 866 pg/mL (follicular RR 30–120 pg/mL; luteal RR 60–350 pg/mL). Pelvic MRI identified bilateral ovarian masses. She underwent bilateral salpingo-oophorectomy with pathology demonstrating benign ovarian fibroma and serous cystadenomas.

Following surgery, estradiol normalized ( < 15 pg/mL). Hypoglycemia also resolved at time of follow-up, with post-oophorectomy CGM showing >93% time in range (RR 70–180 mg/dL). Insulin autoantibodies became undetectable and remained negative at 12-month follow-up.

Conclusion
This case highlights hormonally mediated IAS as a rare cause of hypoglycemia in nondiabetic patients. Insulin autoantibodies can bind circulating insulin and release it unpredictably. Estrogen enhances insulin sensitivity, and the cyclical symptom pattern with sustained biochemical remission after oophorectomy supports hormonal modulation of autoantibody activity. The 15-year latency from bariatric surgery was atypical for post-bariatric hypoglycemia, underscoring the importance of a broad differential in complex hypoglycemia.

*Unless otherwise noted, all abstracts presented at ENDO must not be released to the press or the public until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.*