SAT378 Unusual Case of Hirsutism From Prolactinoma Induced Dihydrotestosterone Elevation

Disclosure: J. Ambalavanan: None. K. Alkwatli: None. L. Tranchito: None. D. Yogi-Morren: None. P.P. Rao: None. Introduction: Hirsutism, in women of reproductive age, is a clinical marker of hyperandrogenism. PCOS is the most common cause while non-classic congenital adrenal hyperplasia, adrenal/ovarian tumors are other causes. While various biomarkers of hyperandrogenism like total testosterone(T), 17-Hydroxyprogesterone(17-OHP), DHEA-S are obtained during evaluation, isolated elevation in dihydrotestosterone (DHT) is rarely seen. We present a unique case of hirsutism where elevated prolactin (PRL) levels from a prolactinoma led to an increase in DHT levels resulting in hirsutism. Case Report: A 31-year-old female presented to the endocrine clinic for hirsutism. Her symptoms included increased chin hair and loss of scalp hair. Symptoms were progressively worsening for a year. Initial biochemical evaluation by an endocrinologist in her home country was significant for subclinical hypothyroidism (SCH) with TSH of 8 mIU/ml (0.35-4.94), elevated PRL of 49 ng/ml(2.8-29.2) and elevated DHT of 871 pg/ml (24-368). T, 17-OHP, DHEA-S were normal. It was believed that her SCH was driving her high PRL and she was started on levothyroxine 12.5 mcg daily along with finasteride 2.5mg daily for high DHT. She denied galactorrhea, breast tenderness headache, vision changes, and menstrual abnormalities. Repeat biochemical testing was performed during the follicular phase of menstrual cycle, after stopping all her pills for 2 weeks. Labs were significant for PRL-102 ng/mL (4.5-26.8), TSH-3.49 mIU/mL (0.27-4.2), total T- 47 ng/dL (8-60), free testosterone - 0.9 ng/dL (0.13-1.03), 17- OHP-70.3 ng/dL (<206), androstenedione-1.7 ng/mL (0.3-3.3), DHT-272 pg/mL (24-208), DHEA-S-386.8 ug/dL (98.8-340), LH-9 mIU/mL, FSH-7.2 mIU/mL. Due to the high prolactin, MRI of the pituitary was obtained and showed a 1.1 cm pituitary adenoma with extension towards optic chiasm. Due to the macroadenoma, we started the patient on cabergoline 0.25 mg p.o. weekly. On repeat testing 1 month after cabergoline, her prolactin normalized to 2 ng/mL (4.5-26.8), dihydrotestosterone normalized to 175.2 pg/mL (24-208), DHEA-S normalized to 220.2 mcg/dL (98.8-340). Conclusion: Elevated DHT is a very rare cause of hirsutism. In our patient, the elevated PRL levels were associated with high DHT and DHEA-S level. Though the exact mechanism of is unclear, studies in rats have shown that prolactin has an activating effect on the 5 alpha reductase enzyme and increases DHT levels. Additionally, treatment of the high PRL levels resulted in normalization of DHT levels. The high DHEA-S was not thought to be a cause of hirsutism as it was normal in the initial labs. Moreover, peripheral conversion would have resulted in high T and androstenedione levels which were normal in our patient. In our review of literature, we could not find any similar reports in human beings and would like to educate the endocrine community of this possible association. Presentation Date: Saturday, June 17, 2023