OP07.03: FSH-secreting pituitary adenoma: a rare cause of ovarian hyperstimulation syndrome

We present two cases of ovarian hyperstimulation syndrome (OHSS) secondary to a follicle-stimulating-hormone (FSH) secreting pituitary adenoma. Case 1: A 36-year-old women presented with acute abdominal pain, nausea and vomiting. Ultrasound revealed enlarged multi-cystic ovaries (right ovary 116x90x80 mm, left ovary 90x60x45 mm) of unknown etiology which on review at a tertiary centre were consistent with hyper-stimulation. Endocrine investigations revealed high estradiol (6992 pmol/L), normal LH (2.4 iu/L) and FSH (10.8 iu/L). MRI pituitary demonstrated a 41mm mass in keeping with a gonadotrophin secreting pituitary adenoma. Trans-sphenoidal resection of the pituitary tumour is planned after endocrine and neurosurgical referral. Case 2: A 31-year-old women was diagnosed with a large pituitary adenoma presenting with symptoms of atrial fibrillation and thyrotoxicosis (T4 30.9 pmol/L, TSH 1.96 mu/L). Further endocrine investigations demonstrated raised estradiol (5738 pmol/L) and FSH (26.7 iu/L) and low LH (<0.5 iu/L). Prior to pituitary adenoma debulking and radiotherapy, pelvic ultrasound revealed a 168x146x94 mm multi-cystic ovarian mass, following treatment the size of the ovaries reduced but continue to appear multi-cystic. FSH secreting pituitary adenomas are a rare cause of OHSS. To date there are only 50 cases reported within the literature. Menstrual disturbance or abdominal symptoms are the most common presentation, leading to a diagnostic challenge for the gynecologist. It is key to consider this diagnosis in women presenting with symptoms and ultrasound images consistent with OHSS in the absence of fertility treatment and pregnancy. Investigations demonstrating the hallmark of raised estradiol, unsuppressed normal high FSH and normal LH should prompt MRI pituitary. Failure to do so could result in delayed or misdiagnosis, inappropriate abdominal ovarian cystectomies or oophorectomies and growth of the underlying pituitary adenoma.