Abstract #1401779: Rare Case of Functional Gonadotroph Adenoma

Abstract

Of all pituitary adenomas, approximately 25-35% are clinically nonfunctioning or "silent" and of those approximately 70-90% are gonadotropin adenomas making them the most common nonfunctional pituitary macroadenoma. However, it is important to know that gonadotropin adenomas can be functional and that gonadotropin excess can result in clinical symptoms and lab abnormalities. This case demonstrates an example of a functional gonadotropin pituitary adenoma overproducing FSH resulting in high-normal testosterone level in addition to compressive symptoms of the optic chiasm. 57-year-old African-American male with pre-diabetes mellitus and gout (only home meds are allopurinoL 300 MG once daily and indomethacin 50 MG three times daily) presented for evaluation of vision loss and large sellar mass on MRI. Vision loss first noted January 2022 along with occasional headaches for 3-4 months (no headaches prior). Patient eventually saw a neuro-ophthalmologist for visual field testing demonstrating left field deficits concerning for optic nerve compression. He then underwent orbital MRI which demonstrated a large sellar mass extending into bilateral cavernous sinus and effacing and displacing the optic chiasm. During visit, patient admitted to fatigue, constipation, polyuria, and nocturia. He denied‌ breast tenderness, nipple discharge, weight change, temp intolerance, skin/hair change, palpitations, tremors, increase hand/foot size, teeth spacing change, worse glycemic control, hypertension, joint pain, acne, hirsutism, striae, clotting disorders, fractures, decreased libido, or erectile dysfunction. He had no known allergies. Blood pressure109/83 | Pulse 101 | Ht 5' 10" (1.778 m) | Wt 88.2 kg (194 lb 7.1 oz) | SpO2 97% | BMI 27.90 kg/m2. Physical exam: Visual fields intact to confrontation but with some patchy deficits in the left eye only. No other notable findings. Subsequent labs demonstrated appropriate cortisol 11.8 ng/dL with normal ACTH of 17 pg/mL, normal IGF-1 of 95 ng/mL, normal TSH of 1.6 uIU/mL with normal free T4 of 0.8 ng/dL. However, prolactin was mildly elevated at 36.5 ng/mL (presumably from stalk effect given size of tumor) and FSH was impressively elevated at 70.3 mIU/mL with a normal LH of 6.5 mIU/mL and a high-normal total testosterone level of 890 ng/dL which was highly suggestive an FSH-producing functional gonadotropin adenoma. It is important to realize the efficacy of surgical resection of functional non-prolactinoma pituitary tumors, especially when the optic chiasm is involved. Patient underwent transsphenoidal resection of pituitary adenoma and indeed pathology revealed a gonadotroph adenoma with SF1 and alpha subunit. He reported slightly improved vision in left eye and had some residual occasional headaches. Awaiting post-operative labs but anticipate normalization of prolactin and FSH and a likely decrease in testosterone level. Awaiting post-operative visual field testing to demonstrate objective improvement. These should be available by the time of the conference.