Are the Sons of Infertile Men Also Infertile?

Is Infertility Genetic?
Believe you me: Nature is complex. (Photo: Annie Spratt, Unsplash.com)

There are certain questions in life that have never been answerable until now. For example, given that many human diseases are treatable, how long can we actually live?  It took the jet age for us to figure out just how much g-force the human body can handle. And it’s only been a hundred years or so since we could imagine life after cancer. Here’s another head-spinner that until recently would have seemed counterintuitive but is now a legitimate question to be addressed: Are the sons of infertile men also infertile?

Fertility from Sterility

Until about 25 years ago, the vast majority of infertile men did not have sons…or daughters. It just didn’t happen. Infertility tends to end things, heirs and all, unfair but square. But with the advent of high-level assisted reproduction like IVF and ICSI, even men with no ejaculated sperm can now be biodads. So, what about their sons? Does male infertility beget more infertility?

There’s a Gene for That

First, some background. Over the past quarter century, we’ve learned that dilated scrotal veins called varicoceles are the most common cause of low sperm counts. Luckily, they are treatable. But the second most common reason for low sperm counts is genetic: either because of mutations on the Y (male) chromosome or alterations to other chromosomes. All in, definable genetic causes of low sperm counts explain about 10-15% of cases. That means that much of male infertility is still unexplained.

There’s also a new kid on the scientific block, epigenetics, and it is neither about mutations nor chromosomes. Instead, it tells us whether genes are activated or turned off. And as this discipline matures in the near future, faulty epigenetics will explain another good-sized chunk of currently “unexplained” male infertility.

All in the Family?

So then, does infertility beget infertility? The answer is a qualified “yes.” Certainly, genetic causes of infertility are likely to be transmitted to offspring. This is especially true of Y chromosome mutations, which by natural law and necessity go from father to son. Other chromosomal issues may or may not be passed down, as God or Darwin has a choice of picking one of two possible parental chromosomes. For good or bad, genetic transmission of disease is pretty linear and predictable, and so it is with male fertility.

Where it gets tricky is when the male infertility is not genetic but epigenetic in nature. Although epigenetic traits are known to be passed to offspring, they can also be modified through lifestyle choices. For example, losing weight, stopping smoking and eating better can alter dad’s epigenetic patterns. This also means that epigenetics might be “fixable” in parents and not necessarily passed to offspring. But that’s about all we know right now.

Infertility due to acquired causes such as infections, cancer or varicocele is unlikely to lead to infertility in sons. This, my friends, is the stuff that we can and should control. However, when low sperm counts have no known cause, the best data available suggests that the sons of men who conceived with IVF-ICSI will also have low sperm counts as adults. Truly a like-father-like-son scenario.

In summary, the answer to the question of whether male infertility is passed down is a fully loaded and complex one. There are things under our control and there are things that aren’t. I’ll modify what Dr. Oz once said thusly: Your genetics load the gun. Your lifestyle [can] pull the trigger.

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