Epidemic of gynecomastia among Haitian refugees: Exposure to an environmental antiandrogen

Objective: To investigate an observed epidemic of gynecomastia among Haitian refugees in US detention centers in 1981 and 1982. Methods: All identifiable environmental exposures were investigated for estrogenic and antiandrogenic activity. Results: A high incidence of gynecomastia was observed among Haitian refugees in five detention centers in the United States. Of 284 men screened, 20 (from 18 to 53 years old) demonstrated new-onset gynecomastia (Tanner stages 2 to 5) in June 1982. The mean onset of gynecomastia was 130 ± 12 days after arrival in the United States. Other symptoms included loss of libido (in all 20 patients) and decreased beard growth (in 10). Plasma concentrations of luteinizing hormone, follicle-stimulating hormone, prolactin, testosterone, and estradiol were not significantly different from those in 20 age-matched control subjects. Environmental substances, including tap water and the delousing agents Kwell shampoo and R&C Spray (applied to bedding and clothing), were tested for estrogenicity and androgenicity. None of these substances bound to cytosol estrogen receptors. The delousing agents were assayed for androgen binding by using genital skin fibroblasts. R&C Spray competed equally with testosterone for androgen-binding sites. Phenothrin, the "multicide" component of R&C Spray, reproduced this competitive binding result. When tested for antiandrogenic effects on prostate growth by using immature male rats treated with testosterone-filled Silastic capsules, phenothrin antagonized androgen action, as demonstrated by decreased prostate weights. Conclusion: The antiandrogenic activity of phenothrin may explain this unusual epidemic of gynecomastia.