SUN-050 Isolated Hyperprolactinemia Caused by Chest Binding in a Transgender Male

Background: Prolactin levels are routinely measured in patients evaluated for PCOS. Compared with the general population, PCOS is more common among transgender men, with prevalence estimates as high as 30 to 50%1,2. Nipple stimulation is a recognized cause of hyperprolactinemia, and many transgender men engage in chest binding, which involves compressing the breast tissue to produce a more masculine appearance. Clinical Case: A 22-year old natal female with gender dysphoria, who presented to our clinic for initiation of masculinizing hormone therapy, revealed a history of irregular menstrual cycles, hirsutism, and moderate acne. The patient was on a combination OCP to regulate menstrual cycles but no other medications or supplements. Laboratory evaluation revealed normal TSH, creatinine, 24-hour urine cortisol, testosterone, 17 hydroxyprogesterone, and DHEA-S. LH was 2.4 mIU/mL, FSH was 6.0 mIU/mL, and prolactin was elevated at 55.6 ng/mL (4.8-23.3 ng/mL). Polycystic ovaries were not present on pelvic ultrasound. Pituitary MRI was ordered for further evaluation of hyperprolactinemia and no pituitary adenoma or other structural abnormality was seen. The patient denied nipple discharge and tenderness but endorsed chest binding. In the absence of another explanation, nipple stimulation through chest binding was hypothesized to be the cause of hyperprolactinemia. After withholding chest binding for one week, the patient’s prolactin level normalized to 13.95 ng/dL. The patient was diagnosed with PCOS according to Rotterdam criteria after exclusion of alternative etiologies. It was presumed that five years of consistent OCP use had normalized androgen levels and suppressed the appearance of polycystic ovaries on ultrasound. The patient was initiated on testosterone cypionate for gender affirmation. Prolactin increased again to 29.33 ng/mL one year later after resumption of continuous chest binding. Conclusion: This is the second reported case of hyperprolactinemia induced through chest binding.3 Transgender men are at increased risk for irregular periods due to underlying PCOS and therefore more likely to undergo an evaluation that includes prolactin measurement. By recognizing chest binding as a cause of isolated hyperprolactinemia, physicians can minimize unnecessary testing and anxiety in patients who engage in this practice.1. Baba, T. et al. Hum Reprod. 2007;22;1011-16. 2. Becerra-Fernandez, A. et al. Endorinol Nutr. 2014;61; 351-8.3. Patel, S., & Abramowitz, J. (2019, April). Hyperprolactinemia in a Transgender Male. Poster session presented at the Annual Scientific & Clinical Congress of the AACE, LA, CA.