An Unusual Cause of Secondary Amenorrhea in an Adolescent: Expanding the Differential

Secondary amenorrhea is not uncommon in the adolescent female population. There are multiple etiologies to consider, and a comprehensive evaluation is often pursued. Sometimes, however, despite a thorough workup, the diagnosis remains unclear. Here, we report an unusual cause of secondary amenorrhea in a 15-year-old girl. Our patient presented with secondary amenorrhea after a 4-year history of regular menstrual cycles. Her evaluation was notable for very low FSH and low estradiol but normal LH; pregnancy, adrenal, thyroid, prolactin studies, and brain magnetic resonance imaging scan did not reveal a cause of her amenorrhea. Her transabdominal ultrasound showed an enlarged right ovary, initially suggestive of a hemorrhagic cyst. Inhibin A and B were measured because of the persistently low FSH; these were found to be very elevated, concerning for an inhibin-producing tumor. The patient had surgical removal of her right ovary; pathology revealed a juvenile granulosa-cell tumor. Postoperatively, the patient had normalization of serum inhibin A and B and resumption of normal menstrual cycles. This report illustrates that careful consideration of laboratory findings and other studies is essential for correctly identifying the underlying cause of secondary amenorrhea, particularly when the results are not consistent with common causes of this condition.