Transgender hormone therapy (male-to-female) males is associated with higher serum estrogen. Both estrogen and testosterone help to stimulate bone formation, especially during puberty. Estrogen is the predominant sex hormone that slows bone loss, even in men. In spite of the induction of breast development, transgender women who undergo HRT do not have an increased risk of breast cancer. Only a handful of cases of breast cancer have ever been described in transgender women who have undergone male-to-female HRT. This is in accordance with research in cisgender men in which gynecomastia has been found not to be associated with an increased risk of breast cancer,
Transgender hormone therapy (male-to-female) voice deepens in pitch and becomes more resonant. These changes are permanent and are not affected by HRT. Voice therapy and/or surgery may be used instead to achieve a more female-sounding voice. Facial hair develops during puberty and is only slightly affected by HRT. It may, however, be eliminated nearly permanently with laser hair removal, or permanently with electrolysis. The psychological effects of feminizing hormone therapy are harder to define than physical changes. Because hormone therapy is usually the first physical step taken to transition, the act of beginning it has a significant psychological effect, which is difficult to distinguish