A testosterone test measures the amount of the male hormone, testosterone, in the blood. Both men and women produce this hormone. In males, the testicles produce most of the testosterone in the body. Levels are most often checked to evaluate signs of low testosterone: In boys -- early or late puberty and in men -- impotence, low level of sexual interest, infertility, thinning of the bones
In females, the ovaries produce most of the testosterone and levels are most often checked to evaluate signs of higher testosterone levels, such as: decreased breast size, excess hair growth, increased size of the clitoris. irregular or absent menstrual periods and male-pattern baldness or hair thinning.