Antiestrogens (or so-called "estrogen blockers") like aromatase inhibitors (AIs) (e.g., anastrozole) or selective estrogen receptor modulators (SERMs) (e.g., tamoxifen) can be used to reduce the effects of high levels of endogenous estrogen (e.g., breast development, feminine fat distribution) in transgender men.
5α-Reductase inhibitors like finasteride and dutasteride can be used to slow or prevent androgenic alopecia (pattern hair loss) and various other adverse androgenic symptoms (e.g., acne) in transgender men taking testosterone.