Objective: To demonstrate the clinical course in a young female with gonadotroph adenoma causing ovarian stimulation. Patient and methods: Our patient was a 23-year-old woman with a history of oligomenorrhea who had previously undergone bilateral ovarian wedge resection owing to the clinical appearance of polycystic ovaries. Two years later, she sought treatment for headache, galactorrhea, history of spotting and lower abdominal distension. FSH, LH, b-LH, inhibin A and B, estradiol, prolactin (PRL), and bchorionic gonadotrophin (b-CG) were measured, and the responses of FSH, LH and b-LH to thyrotrophin-releasing hormone (TRH) were documented. Immunohistochemical analysis of the tumor tissue was performed after surgery. Five years after the trans-sphenoidal surgery, the patient again became oligomenorrheic. A large recurrent adenoma was diagnosed on CT one year later. Transvaginal ultrasound showed ovaries of normal size with multiple small cystic formations simulating a polycystic pattern, While the patient was awaiting surgery, a pituitary apoplexy occurred. Emergency decompressive surgery was performed and the patient fully recovered. Results: Enlarged ovaries were found on ultrasound examination simulating a hyperstimulationlike pattern. At that time, elevated levels of FSH (13.4 IU/l) and marginally elevated levels of b-LH (1.43 ng/ml) were found, whereas the level of LH (0.5 IU/l) was subnormal. Plasma estradiol was markedly supranormal (6150 pmol/l). Levels of inhibin A and B were elevated (326 pg/ml and 588 pg/ml respectively). The prolactin level (70 ng/ml) was increased, whereas b-chorionic gonadotrophin (b-CG) was normal. Signi®cantly increased FSH, LH, and b-LH responses to TRH stimulation were documented. Pituitary macroadenoma was found on MRI scan and removed by trans-sphenoidal surgery. Immunohistochemical examination showed high positivity for b-CG and LH, and slight positivity for FSH. Five years after the surgery, estradiol was elevated (1160 pmol/l), whereas basal levels of LH (4.65 IU/l) and FSH (3.98 IU/l) were not suppressed. After the second operation, immunostaining of the adenoma tissue con®rmed the previous ®ndings. Conclusions: Measurement of gonadotrophins in our case did not prove to be a method for identifying a large recurrent gonadotroph pituitary adenoma. The sonographic ovarian imaging varied from a polycystic-to an ovarian hyperstimulation-like pattern during the evolution of the tumour.