PURPOSE: Gonadotroph adenomas are pituitary adenomas with inefficient and variable secretory characteristics, that is why they are usually considered as a subgroup of nonfunctioning pituitary adenomas (NFPA) and are recognized only at immunohistochemistry. When gonadotroph adenomas secrete active hormones, they may cause spontaneous ovarian hyperstimulation syndrome (OHSS) in premenopausal women. Aim of our study is to describe three women with OHSS diagnosed before the removal of the adenoma and to calculate the prevalence of OHSS in premenopausal women with a clinical diagnosis of NFPA. METHODS: We reviewed clinical records of premenopausal women that underwent neurosurgery for NFPA at our centre between 1993 and 2014. OHSS was diagnosed in patients with high levels of FSH, suppressed LH, hyperestrogenism, abdominal symptoms, polymenorrhea, enlarged ovaries with cysts or previous surgery for ovarian cysts. RESULTS: 171 women were included into the study; 62 (36.6%) had a gonadotroph adenoma diagnosed at immunohistochemistry. Two patients were retrospectively diagnosed as having OHSS due to gonadotroph adenoma and three had OHSS diagnosed before neurosurgery. The prevalence of OHSS was 2.9% in the overall group of patients with NFPA and 8.1% among patients with a gonadotroph adenoma detected at immunohistochemistry. CONCLUSIONS: Frequency of OHSS due to a gonadotroph adenoma is not negligible. Increased awareness of the characteristic clinical and hormonal picture should permit an early detection of this condition in premenopausal women with a pituitary adenoma.