The effects of clomiphene in men are increased production of testosterone and therefore increased production of sperm. The drug works by disrupting the system which usually tells the pituitary gland to stop producing testosterone. This system involves the pituitary gland within the brain and the Leydig cells in the testes. Studies have shown that the use of clomiphene in men is not as effective as in women — but this is consistent with data that show that couples are less likely to get pregnant if the man has to use fertility drugs rather than the woman. Clomiphene is not approved by the United States Food and Drug Administration (FDA) for use in men.
Understanding the effects of clomiphene in men requires general knowledge about the process of testosterone production. The pituitary gland releases a hormone called luteinizing hormone (LH), which is transported to the Leydig cells in the testicles and serves as a chemical messenger. Leydig cells receive the LH and begin to make testosterone, pumping it out into the body. The testosterone released into the body is converted into estrogen, which makes its way back up to the pituitary gland. The pituitary takes the excess of estrogen as a signal to reduce output of LH and therefore of testosterone.
The use of clomiphene in men disrupts this process. The drug stops the estrogen from reaching the pituitary gland, which makes the pituitary gland think that there is not enough testosterone in the body. The pituitary sends more LH down to the Leydig cells in the testes, which respond by making yet more testosterone.
A by-product of this hormonal process has lead to the use of clomiphene to raise the sperm count in men and improve the quality of the sperm. This can occur as a result of the excess testosterone produced by the Leydig cells. The extra testosterone corrects hormone levels, which can lead to healthier sperm.
Despite the positive results of tests into the effects of clomiphene in men, the drug is still not FDA approved for use in men. This is because the company who originally applied for approval did so specifically for the use of the drug in women. Research has shown that couples where the man needs fertility treatments only get pregnant 20 to 25 percent of the time, compared with 20 to 60 percent when the woman is taking the treatments.