Isolated FSH deficiency revealing a granulosa cell tumor

We report a case of a 41-year-old woman with a recent secondary amenorrhea and infertility. The initial assessment ruled out premature ovarian failure, polycystic ovary syndrome and led to suspect a hypothalamo-pituitary cause. However, the unusual hormone pattern with a very low level of FSH, normal levels of LH and estradiol, associated with a positive progesterone test suggested the presence of a FSH inhibiting factor: the unexpectedly high levels of inhibin B and AMH were suggestive of a granulosa cell tumor as showed by the radiologic findings. This prompted a surgical exploration, which confirmed the putative diagnosis. This case report illustrates the inhibin B and AMH values and the modern-day pelvic imaging data encountered in menstrual irregularities caused by a granulosa cell tumor.