Testosterone is one of the hormones needed for sexual development and is present in both males and females. Testosterone is considered an androgen, which is a male sex hormone, because it is made in much higher amounts in men than in women.

Testosterone helps strengthen bones and muscles in both men and women. In young men, testosterone signals the body to lower the voice, grow facial hair, and develop sexual characteristics. This hormone is also needed for sperm production.

In a lactating woman, more prolactin is produced when her breasts are emptied frequently, resulting in more milk production. Less frequent emptying of the breasts reduces the amount of prolactin produced, which in turn reduces the milk supply. Above-normal prolactin levels in women can cause ovulation to stop.

Above-normal levels of prolactin can indicate a problem with the pituitary gland that may affect reproductive functions.