Ovarian hyperstimulation syndrome is characterized by enlarged ovaries, multiple follicular cysts, and fluid leakage into the extravascular space caused by increased vascular permeability. Although controlled ovarian stimulation is often the main cause, spontaneous ovarian hyperstimulation syndrome is rare.

We present a seventeen-year-old patient with ovarian hyperstimulation syndrome and primary hypothyroidism due to autoimmune thyroiditis, who presented with galactorrhea and severe abdominal pain. The thyroid-stimulating hormone level was 713 uIU/ml. Ultrasonography and magnetic resonance imaging showed ovarian enlargement and multiple cysts. Our patient, who also had galactorrhea and hyperprolactinemia, was treated with levothyroxine and cabergoline. The ovaries, which were very large and multicystic before treatment, showed significant improvement after treatment.

Spontaneous ovarian hyperstimulation syndrome, although rare in childhood, should be considered in patients with primary hypothyroidism. Abdominal pain is an important symptom for diagnosis.