Bicalutamide, a new anti-androgen for trans women and girls

Disclaimer: I am not a doctor, and this is not medical advice. Do not take any medication without appropriate medical supervision.

Previously I’ve looked at low-cost alternatives to GnRH analogue puberty blockers for trans adolescents, including medroxyprogesterone acetate, spironolactone, cyproterone acetate, and norethindrone. One new option for trans girls has recently been studied: bicalutamide (Casodex), an oral nonsteroidal anti-androgen used to block testosterone in cases of prostate cancer.

Bicalutamide works by directly blocking the action of androgens at the androgen receptor. It is not an antimineralocorticoid like spironolactone, a glucocorticoid and synthetic progestin like cyproterone acetate, or a DHT blocker like finasteride or dutasteride. For this reason, bicalutamide may be an option for trans women who can’t tolerate the side effects of other anti-androgens, and past publications on hormonal treatment have listed bicalutamide as having a potential role in HRT.

The newest study by a team at the Indiana University School of Medicine and Riley Hospital for Children is the first to look at bicalutamide as a puberty blocker and feminizing medication in adolescent trans girls. The authors found that bicalutamide at 50mg a day produced suppression of testosterone as well as development of breast tissue:

Results: Of 77 patients with GD identified, 29 were MTF, of whom 14 (48%) aged 15.8 ± 1.9 years (range 12-18.4yr) were treated with bicalutamide 50 mg daily between 2013 and 2017. Of these, 3 were started on estrogen concurrently whereas 11 received bicalutamide alone, 7 of whom have returned for follow up thus far. After an average of 5.7±1.5 months, 86% of the patients (n=6) had breast development consisting of Tanner stage III in 4, Tanner stage II in 1, and Tanner stage III/II of the right and left breast in 1. The 7th patient was noted to have Tanner III breasts at her 2nd follow-up clinic visit 12.5 months after starting bicalutamide. LFTs were obtained on 4 patients, estradiol on 3 patients and testosterone on 2 patients while exclusively taking bicalutamide. LFTs were unremarkable and concentrations of estradiol and testosterone were 26-61 pg/mL and 524-619 ng/dL, respectively.

Bicalutamide is available as a generic medication for less than $20 a month. Given that GnRH analogue puberty blockers can cost thousands of dollars and may not be covered by insurance, this lesser-known anti-androgen may be an economical option for adolescent trans girls. ■