Testosterone also affects various other tissues in the male. Testosterone causes pubic and underarm hair growth, causes changes in body propor- tions, increases muscle tissue, and deepens the voice. Testosterone may influence the development of acne and the beginning of body odors from bacteria attracted to sweat glands. Because none of these characteristics are directly related to sexual reproduction, they are called secondary sex characteristics. In males, the level of testosterone in the body remains much the same for about 40 years after puberty. After that time, the level of testosterone gradually begins to decrease
