The affect of the pituitary hormones, FSH and LH were shown to stimulate the production of androgens. The primary male androgen, testosterone was discussed first by comparing its structure to that of the female hormone estrogen. The nearly identical structural formulas was used to explain that some testosterone is converted to estrogen in the male. The main function of testosterone in the male was listed, including its effect on hair growth, muscle development, deeper voice, development of gonads, secondary sex organs, aggression, and libido.