In men with idiopathic infertility, baseline age, body mass index, treatment duration, and levels of testosterone, FSH, LH, estradiol, and 17-hydroxyprogesterone do not reliably predict changes in total motile sperm count following clomiphene citrate therapy.

Clomiphene blocks estrogen from signaling the brain to stop producing hormones that tell the testes to make sperm and testosterone. This causes the brain to release more of those hormones, which then boost testosterone inside the testes and activate sperm production, leading to more motile sperm. But the amount of sperm each man makes in response depends on unknown factors in his testes, not on his age, weight, or initial hormone levels.