SAT-269 A Rare Case of Functioning Gonadotroph Producing Pituitary Macroadenoma in Teenage Male

Background: Unlike nonfunctioning gonadotroph pituitary adenomas, functioning gonadotroph pituitary adenomas (FGA) are an uncommon type of pituitary tumors that secrete biologically active gonadotropins (LH, FSH, or both). Clinical Case: A 23-year-old man with no previous medical history presented to the emergency department with three months history of progressive decreased vision and decreased libido. He denied headache, seizure, erectile dysfunction, or weakness. On physical examination, his visual acuity was significantly reduced on the right eye and was only able to perceive light. He had a visual field narrowing on the left eye. Gynecomastia was noted bilaterally and testicles were found to be enlarged (Orchidometer >25 mL). Complete blood count was significant for hemoglobin of 19.2 g/dL (N, 13.7-17.5 g/dL), and hematocrit of 57.0% (N, 40.1-51.0%). Pituitary function tests were as follow: FSH >200.0 mIU/mL (N, 1.5-12.4 mIU/mL), LH 17.0 mIU/mL (N, 1.7-8.6 mIU/mL), total testosterone 41.3 nmol/L (N, 8.6-29.0 nmol/L), free testosterone 1.263 nmol/L (N, 0.148-0.718 nmol/L), and bioavailable testosterone 29.609 (N, 2.110-8.920 nmol/L). Prolactin, TSH, GH, and ACTH were all within the normal range. Magnetic resonance imaging (MRI) showed a sellar mass involving the planum sphenoidal measuring 5.8 x 5.2 x 5.6 cm with optic chiasm displaced superiorly, in addition, subfalcine herniation with mild hydrocephalus was also noted. The patient underwent orbitozygomatic approach resection of the pituitary tumor. Histological examination was consistent with a pituitary adenoma. Cells stained positive for transcription factor steroidogenic factor 1 (SF 1), FSH, LH, and alpha-subunit consistent with a gonadotroph adenoma. They were negative for transcription factor Pit 1 stain and the remaining pituitary hormones including ACTH, GH, prolactin, and TSH stain. Postsurgical hormone assessment showed a significant decline in FSH and LH to 2.3 and 0.4 mIU/mL, respectively and testosterone level decreased to < 0.087 nmol/L on postoperative day 18. The patient’s vision improved postoperatively prior to discharge but he lost follow up thereafter. Conclusion: Most patients with functioning gonadotroph pituitary adenoma present with large tumors that are detected based on the occurrence of symptoms of compression that result from the enlarging sellar mass. Most patients, particularly men and postmenopausal women, do not develop symptoms of hormone excess and the lack of symptomatology results in delay in diagnosis. Our patients presented with significant polycythemia which resulted from excess testosterone and could have prompted earlier tumor detection if he had presented in an earlier stage. The incidence of polycythemia in male patients with functioning gonadotroph pituitary adenoma has previously been described in the literature in a few case reports.