TSH-induced post thyroidectomy spontaneous ovarian hyperstimulation syndrome: a rare case report of molecular mimicry

Background: Spontaneous ovarian hyperstimulation syndrome (sOHSS) is an exceptionally rare condition, particularly when associated with profound primary hypothyroidism (Type III sOHSS). Unlike the common iatrogenic form, it occurs without exogenous ovulation induction. Case Presentation : We report a 26-year-old female with a history of total thyroidectomy for papillary carcinoma who presented to the emergency department with severe abdominal pain, diarrhea and tense ascites. Laboratory evaluation revealed a critical elevation of thyroid-stimulating hormone (TSH) and normal follicle-stimulating hormone (FSH) levels. Imaging confirmed bilateral multicystic ovarian enlargement and massive ascites. The clinical presentation was consistent with OHSS triggered by "specificity spillover," where extreme TSH levels cross-activate FSH receptors. Conclusion: Prompt recognition of severe hypothyroidism as a cause of sOHSS is vital to avoid unnecessary surgical interventions. Management centered on levothyroxine replacement and supportive care resulted in the complete resolution of symptoms and radiologic findings, with a satisfactory clinical evolution.