by Christine Haran
Certain men worry about their sperm count, whether or not they are in the process of trying to have a child. Other men might find a low sperm count unimaginable. In reality, a low sperm count is the most common reason for male infertility.
A study published this fall in the journal Fertility and Sterility found that men who were very overweight or underweight had lower sperm counts than men who were at an ideal weight. The good news that can be taken from this study is that while low sperm count is sometimes genetic, some manageable factors can contribute to sperm count. And even people with genetic problems may achieve conception with the help of technology.
Sperm is manufactured in the testicles, which are organs that are suspended in the scrotum. As you probably know, sperm is the component in semen that has the potential to fertilize a woman's egg and lead to pregnancy. According to the World Health Organization, a sperm count of more than 20 million sperm per milliliter of semen is considered normal.
"If you have no sperm, you're not going to be able to conceive," says Jon Pryor, MD, chair of the department of urologic surgery at the University of Minnesota. "When you have a sperm count of less than 5 million, it's going to be very difficult. But does someone who has a sperm count of 20 have more difficulty conceiving than someone at 50 or 60? Probably not."
Of course, sheer numbers are not the only consideration. Quality counts, too. For example, sperm shape, as well as sperm motility, or movement, also play important roles in conception. Reproductive specialists suspect that other factors unrelated to sperm health are also at work in fertility, but these are not yet understood.
"We're in our infancy in figuring out why people have trouble conceiving," Dr. Pryor says. "The first things that hit you over the head are the number, movement and shape of the sperm, but there are probably hundreds of different biochemical and molecular reactions that happen for fertilization and a successful pregnancy to occur."
Still, there is no doubt that sperm count is important, so men who are interested in fatherhood should do what they can to keep counts high. The most common identifiable cause of low sperm count is variococles, which are dilated, or expanded, veins in the scrotum. Varicocles are seen in about 15 percent of all men and 40 percent of men with infertility.
It's theorized that variococles hurt sperm production by heating up the testicles, but this effect is not completely understood. Dr. Pryor says that surgically blocking the dilated blood vessels so the blood is re-routed improves sperm counts about two-thirds of the time.
Another 15 percent of men have no sperm in their semen, a condition called azoospermia. In some cases, this may be the result of a genetic problem. In others, a blockage has occurred somewhere along the sperm's pathway. This includes the testicles, the epididymis, a structure behind the testicle, the vas deferens, a tube that takes the sperm behind the bladder to the prostate, and a gland called the seminal vesicle. Such blockages can result from an injury or infection. In these men, surgery to undo or bypass the blockages solves the problem.
Other men may have hormone irregularities that affect stimulation of the testicles and inhibit sperm production; adjusting hormone levels usually normalizes their sperm counts.
Aside from these medical problems, "the overall health of men is the only thing that is critically important," says Peter N. Schlegel, MD, chair of the department of urology at the Weill Medical College of Cornell University in New York.
In the Fertility and Sterility study of 1,558 Danish men, a high or low weight, as measured by body-mass-index (BMI), influenced sperm count, but not sperm motility or shape. While it was not clear why the men with low BMI had low sperm counts, the researchers wrote that hormone imbalance might be a factor, and that some of these men might have suffered from malnutrition or other health problems.
The study did show that testosterone levels were lower in obese men than men of ideal weight, and indicated this change was a probable cause for the decrease in sperm count.