Ovarian hyperstimulation syndrome without gonadotropin stimulation: an unusual response to a GnRH agonist

Ovarian hyperstimulation syndrome (OHSS) is a well-known iatrogenic complication of ovarian stimulation with gonadotropins. We present the case of a woman in her 30s who developed OHSS without the administration of gonadotropins. She was due to undergo intracytoplasmic sperm injection (ICSI) for primary subfertility. After taking a gonadotropin-releasing hormone (GnRH) receptor agonist for 3 weeks, she presented with abdominal pain, nausea and bloating. She was diagnosed with moderate to severe OHSS, requiring management as an inpatient.Investigations included a pelvic ultrasound scan showing an enlarged ovary, serum oestradiol >30 000 pmol/L and an MRI of the brain with an incidental finding of a 5 mm pituitary microadenoma.She recovered rapidly and was referred for endocrinology evaluation and multidisciplinary team discussion. The OHSS was felt to be explained by an unusual 'flare' response to a GnRH agonist. A further ICSI cycle with an antagonist protocol is planned.