Many people have claimed positive outcomes when using melatonin for inducing sleep. Melatonin is a substance that your brain's pineal gland secretes, producing the effect of sleepiness. It has been used as a supplement for those who work irregular hours and by some recovering from jet lag. While the effects of melatonin can be beneficial for sleep cycles, it has many side effects that influence various body systems.
Melatonin produces side effects in men that affect reproductive functions. It has been shown to decrease the amount of sperm in men and affect sperm motility, according to the Mayo Clinic. These side effects disrupt reproduction as lower numbers of sperm decrease the chance of conception. Slow motility affects how sperm swim, preventing them from reaching an egg for fertilization.
Melatonin may produce side effects that affect hormone levels in women, including changes in the levels of progesterone, estradiol, luteinizing hormone and thyroid levels. The Mayo Clinic reports that alterations in the levels of these hormones affect the process of ovulation and menstruation, which can cause problems with conceiving or maintaining a pregnancy.
While melatonin is helpful for inducing sleep, it can inhibit the sex drive, according to Newsweek. People who take high doses of melatonin as a supplement may find they have less interest in sex—a situation that affects reproductive function simply by lack of activity.
According to the University of Maryland Medical Center, melatonin affects a woman's menstrual cycle, including the onset of menstruation, the regularity of menstrual cycles and the start of menopause. Melatonin side effects can influence the balance of the menstrual cycle, affecting ovulation. The result can be difficulty determining ovulation when trying to conceive, causing problems with fertility.