Spironolactone vs. bicalutamide in female pattern hair loss: a randomized clinical trial

Antiandrogen therapy is a cornerstone in managing female pattern hair loss (FPHL), yet comparative efficacy data between commonly used agents such as spironolactone and bicalutamide are limited.

To compare the efficacy and safety of bicalutamide (50 mg day-1) vs. spironolactone (100 mg day-1) monotherapy in women with FPHL.

This randomized, double-blind, parallel-group clinical trial was conducted at a tertiary care centre in India between February 2024 and March 2025. In total, 204 women aged 18-50 years with Sinclair grade II-V FPHL were randomized. Participants received either spironolactone 100 mg day-1 or bicalutamide 50 mg day-1 orally for 24 weeks. Trichoscopic assessments were performed at baseline and 24 weeks. Primary outcomes were changes in hair density and shaft diameter at two fixed scalp points [12 cm (frontal) and 24 cm (vertex) from the glabella]. Secondary outcomes included global photographic assessment, reduction in Sinclair hair shedding score and safety profile. The trial was registered with the Clinical Trials Registry of India (CTRI/2024/01/062101).

Of 204 randomized participants, 188 (92.2%) completed the trial. The mean (SD) increase in hair count at the frontal site was 5.05 (3.61) hairs cm-2 in the bicalutamide group vs. 3.13 (2.62) hairs cm-2 in the spironolactone group [mean difference 1.92; 95% confidence interval (CI) 1.01-2.62; P < 0.001]. At the vertex site, the increase was 6.32 (9.38) vs. 3.06 (10.76) hairs cm-2, respectively (mean difference 3.26; 95% CI 0.35-6.08; P = 0.028). Hair shaft diameter increased more with bicalutamide at both sites [mean difference 2.87 μm; 95% CI 2.12-3.32 (frontal) and 2.10-3.36 μm (vertex); P < 0.001 for both]. Adverse events were reported in 18.6% of spironolactone-treated and 11.7% of bicalutamide-treated participants.

Bicalutamide produced greater trichoscopic improvements than spironolactone; however, no significant between-group differences were observed in clinical endpoints. Limitations include a short follow-up period, single-centre design and per-protocol analysis, which may limit generalizability.