Ovarian hyperstimulation syndrome (OHSS) usually occurs after induction of ovulation for in-vitro fertilization. It is rarely seen spontaneously in pregnant females. This syndrome is life threatening complication with a range of symptoms, including abdominal distention and discomfort, dyspnea, enlarged ovaries, ascites, hemoconcentration, hypercoagulability, electrolyte imbalances and oliguria.

This case report presents a unique case of spontaneous OHSS in a 13-year-old premenarchal female with primary hypothyroidism. The patient presented with abdominal pain, ascites, and a significant ovarian mass, along with laboratory findings including severe anemia, kidney dysfunction, and elevated thyroid-stimulating hormone levels and estradiol. Imaging revealed enlarged, multicystic ovaries. Following diagnosis, the patient was managed with thyroid replacement therapy, broad-spectrum antibiotics, and hemodialysis for acute kidney injury. Despite initial improvements, she developed cerebral venous sinus thrombosis, which was treated with anticoagulation. Over one month of treatment, her ovarian cysts reduced significantly with thyroxine therapy.

Therefore, it is essential for clinicians and radiologists to familiarize themselves with the clinical symptoms and imaging findings associated with spontaneous OHSS in the context of primary hypothyroidism. Understanding these aspects will enhance their ability to diagnose and manage this condition effectively and avoid life threatening complications and unnecessary surgery.