However, the oxidized form of the hormone, testosterone, promotes secondary sex characteristics. Thus, an XY child without functioning 5α-reductase cannot convert testosterone into the form that develops primary sex characteristics and will have the appearance of female genitalia. At puberty, when large amounts of testosterone are produced, secondary sex characteristics (e.g., deepening voice, hair pattern changes, muscle anabolism, etc.) develop, thus producing a phenotypic male.