A large study published in 2013 reveals a markedly reduced incidence of breast cancer in women treated with testosterone compared to women who received no hormone replacement therapy. (Glaser et al, Maturitas 2013)
1268 women were enrolled in the study, with average follow-up of five years. Treatment was provided with testosterone pellets implanted under the skin of the buttock or abdomen under local anesthesia, repeated every 3-4 months. About half of the implants contained testosterone alone, while the rest included anastrozole as well. Anastrozole blocks the conversion of testosterone into estrogen, offering added safety.
The incidence of breast cancer in the testosterone-treated group was only half that of women who did not receive hormones.