Growing evidence indicates that androgens play a positive role in follicle proliferation and growth. Hence, many authors have assumed that androgen supplementation in women with poor ovarian reserve might improve the number of antral follicles available for ovarian stimulation. As androgen administration may become more frequently used in reproductive medicine, this study aimed at describing the histological changes observed in the genital tract and the breast of female-to-male (FTM) transsexuals. A pathological analysis of the genital tract of 112 FTM subjects who were given androgen for at least 6 months before hystero-salpingo-oophorectomy was performed. In addition, 100 bilateral mastectomies were performed, allowing a study of the breast tissue. Mean ovarian volume was increased, with histological characteristics of polycystic ovaries (PCO), defined as >12 antral follicles per ovary, observed in 89 patients (79.5%). Endometrial atrophy was observed in 45%. Breast examination revealed marked reduction of glandular tissue and increase of fibrous connective tissue in 93%, without atypical hyperplasia or carcinoma. The present data confirms and expands the putative associations between long-term androgen administration and abnormalities in ovarian architecture with macroscopic and microscopic characteristics of PCO, increased risk of endometrial atrophy and fibrotic breast tissue with marked glandular reduction.