Are men with one instead of two testicles less fertile?

Men usually have two testicles and both testicles produce sperm. There are several instances where a man would have one instead of two functioning testicles:

• Crytorchism: One testicle is descended and the other is undescended, still higher up outside the scrotum inside the abdomen
• Surgery: A testicle can be surgically removed for several reasons such as injury or tumors
• Congenital: Some men are born with only one testicle

How would the presence of one instead of two testicles, or being born with only one testicle, impact fertility? The answer is that a man with one testicle generally produces just as much sperm as a man with two testicles. But to make sure, doing a sperm analysis would confirm this.

Take our male fertility test and learn if you (or your partner) are fertile.

Semen and sperm production

If a man is born with two testicles, and they are both in the scrotum, then he will produce sperm and semen in both. Tubes connect the testes to the penis where semen and sperm are moved out of the body during ejaculation. If one testicle is not present at birth or if one is removed at some point in life, the other testicle usually takes over semen and sperm production, but to make sure, a sperm analysis is needed.

There could be reduced semen production as a result of having only one testicle, and sometimes it depends on why there is only one testis, but in most cases, fertility is not affected.

Let’s take a look at this in numerical terms. Sperm production in excess of 20 million per sample is considered normal. If a man produces 100 million sperm with two testicles and that number is cut in half due to the loss of one testicle, sperm production is still within normal levels. However, the remaining testicle will pick up sperm production so the total number of sperm may not be halved in a real-life situation, so more than 50 million sperm could be produced in reality. 

What about those rare cases?

Sure, there are rare cases where testicle removal or being born with only one testicle affects fertility, but it takes only one sperm to fertilize the egg, so any production is good enough for conception with assisted technology, in most cases.

If you feel you could be producing less sperm than needed to conceive and you’ve been having problems with fertility, a sperm analysis can put your mind at ease. Sometimes, the cause of infertility has nothing to do with sperm production at all. It can be nice to see the normal numbers on paper which may be enough to reduce stress and increase your chances of natural conception.

Source: Lee PA, Coughlin MT. The single testis: paternity after presentation as unilateral cryptorchidism. J Urol. 2002 Oct;168(4 Pt 2):1680-2;