SUN-118 A Case of Anastrozole Induced Hyperandrogenism

Abstract Disclosure: R. Anil: None. T. Khoo: None. We report a rare case of hyperandrogenism in a 74-year-old post-menopausal woman on Anastrozole for treatment of ER +ve, grade 1, invasive breast cancer. Case: 74-year-old woman with type 2 diabetes, after being diagnosed with Stage 1, invasive, ER +ve, left breast cancer in 2021, underwent lumpectomy as well as adjuvant radiation and was placed on anastrozole. She presented to endocrinology office in 2023 with 6 month history of hirsutism, requiring regular shaving and scalp hair thinning. She was also found to have elevated hemoglobin levels at PCP office. On work up she was found to have elevated total testosterone (843), with normal PM cortisol, 24-hour free urine cortisol and adrenal androgens. Pelvic US was normal, excluding ovarian hyperthecosis as well as ovarian masses. CT abdomen was negative for any adrenal lesions. Testosterone levels were found to be 200 points lower when repeated after holding anastrozole for 2 weeks. After exclusion of other causes, it was concluded that her symptoms and elevation in testosterone levels were likely secondary to anastrozole. Oncology recommended that the patient continue an aromatase inhibitor. Patient was switched from anastrozole to exemestane by her oncologist and was started on spironolactone for persisting hirsutism and scalp hair thinning. Discussion: Anastrozole, being a selective non-steroidal aromatase inhibitor, inhibits the conversion of testosterone to estradiol and has the potential to cause testosterone excess. Anastrozole has been reported to increase testosterone levels, with studies done mostly in men, however the degree of elevation is not well described. Hyperandrogenism, which manifests as hirsutism, male-pattern baldness, acne, clitoromegaly and other virilizing features, in post-menopausal women, is usually concerning for ovarian hyperthecosis or androgen-secreting tumor. There is evidence in literature of concurrent use of anastrozole masking ovarian hyperthecosis. Hence in such cases it is imperative to rule out the serious causes of hyperandrogenism before attributing it to aromatase inhibitors. Conclusion: Anastrozole as a cause of hirsutism or hyperandrogenism has not been commonly described and may be considered after exclusion of more serious causes. References: Dias JP, Melvin D, Simonsick EM, Carlson O, Shardell MD, Ferrucci L, Chia CW, Basaria S, Egan JM. Effects of aromatase inhibition vs. testosterone in older men with low testosterone: randomized-controlled trial. Andrology. 2016 Jan;4(1):33-40. doi: 10.1111/andr.12126. Epub 2015 Nov 20. PMID: 26588809; PMCID: PMC5836312.Khan, Muhammad & Ahluwalia, Rupa & Shore, Susannah & Waghorn, Alison & Vora, Jiten. (2014). Hyperandrogenism secondary to ovarian hyperthecosis masked by concurrent use of an aromatase inhibitor: a case report. Endocrine Abstracts. 10.1530/endoabs.34.P339. Presentation: Sunday, July 13, 2025