Testicles FAQ

Medically Reviewed by Dan Brennan, MD on February 14, 2024
Written by Hedy Marks
5 min read

Testicles, also called testes or balls, are oval-shaped organs that sit in a sac that hangs behind the penis.

The main job of testicles is to make sperm and produce testosterone. Testosterone is the male hormone that's responsible for the changes that occur during puberty. Puberty is the time in life when your body begins to change and you start to look more and more like an adult.

After puberty is finished, the testicles will produce millions of sperm a day. Sperm mixes with a white, milky substance to make semen. Semen is what's released from the penis when you ejaculate.

Guys become fertile between the ages of 11 and 17, meaning they are able to ejaculate semen and get a girl pregnant.

Your testicles will grow in the early stages of puberty, between the ages of 10 to 13. As your testicles grow, the skin around the scrotum -- the sac that holds the testicles -- will darken, hang down, and begin to develop hair.

On average, testicles grow to be about 2 to 3 inches in length and 1 inch in width.

Yes. It is common for guys to have slightly different size testicles. Usually, the right testicle is larger than the left. Also, one testicle (usually the left) often hangs lower than the other.

For your testicles to produce sperm, they must be kept at just the right temperature. As a result, the scrotum will change size to make sure the testicles stay at that right temperature. This happens without you even thinking about it. So, when you are cold, your body sends a message to the scrotum to shrivel and preserve heat.

Just as your body directs your scrotum to shrivel when it is cold, your body tells the scrotum to loosen up when you are too warm. Your scrotum will become larger and more floppy to release extra heat.

Many things can cause painful or swollen testicles, including:

  • Fluid collecting in an area surrounding a testicle, a condition known as a hydrocele.
  • Infection, such as from a virus or a sexually transmitted disease (STD) like chlamydia
  • Inguinal hernia. That's a condition in which a part of the intestines pushes into the groin or scrotum through an abnormal opening or a weak spot in the abdominal wall.
  • Injury to the testicles, such as from being kicked, hit, or crushed.
  • Swelling in a vein that drains blood away from a testicle, a condition called varicocele.
  • Testicular cancer.
  • Testicular torsion, an extremely painful condition that occurs when a testicle gets twisted.

If you think you have testicular torsion, see a doctor right away. This is a serious medical emergency.

If you notice any pain or swelling in or around your testicles, tell a parent and have it examined by a doctor as soon as possible. Many different types of testicle problems are linked to pain and swelling in the testicles. It's not always easy to tell which episode could lead to more serious problems if ignored. Play it safe and get checked.

Testicular cancer occurs when cells in the testicle divide abnormally and form a tumor. You may think you're too young to worry about it. But you're not, especially if you’re over the age of 14. Testicular cancer typically affects males between the ages of 14 and 35. And it's the most common cancer in this age group.

Testicular cancer is not very common. There are about 8,300 new cases a year. And about 500 men die each year from this cancer. But while some men are more likely to get it than others, it's possible for any young man to get the disease.

The most common symptom of testicular cancer is a painless lump on a testicle. Other symptoms may include:

  • An enlarged or swollen testicle, with or without pain
  • A heavy, aching feeling in the lower stomach, low back, or groin

Unless you have certain risk factors, such as a brother or father who has or had testicular cancer, the American Cancer Society (ACS) says there aren't enough studies to make monthly exams a recommendation.

But, because the cancer is so easy to treat when found early, some doctors recommend the exam. Besides finding cancer early, the exam can help you find other problems that may need to be treated.

Some doctors recommend that boys start doing monthly exams as early as 14. At this age, it's unlikely that you’ll find anything to be concerned about. However, a self-exam will give you the chance to get to know your body so that you can detect changes more easily in the future.

The best time to do an exam is right after a shower or bath. That's when the skin of the scrotum will be most relaxed and the exam will be easier to do. You should do the exam standing in front of a mirror. If you are nervous about touching yourself, don't be. This is how you get to know what your testicles and scrotum should feel like.

  • Start by standing in front of the mirror and checking for any swelling in the scrotum. Cup the scrotum in one hand to see if it feels normal.
  • Hold your penis out of the way and examine one testicle at a time.
  • Roll the testicle gently between the fingers and thumb. You should not feel any pain.
  • The testicle may be about the size of a golf ball, and it should feel smooth.
  • Feel for any bumps or changes in size or consistency.
  • After checking one testicle, check the other the same way. One testicle may be slightly larger or smaller; this is normal.
  • Lumps should be checked by a doctor.

You may notice bumps on the skin of your scrotum. These are often caused by an ingrown hair or by a rash. They are usually not a cause for concern. You may also feel small, squishy lumps of tubes. These tubes are the sperm tubes that connect your testicles to the rest of your body. These small bumps are normal. But anything that feels different than usual should be checked by a doctor.

If you find any lumps on your testicles when you do a self-exam, see a doctor right away. Also see a doctor if you notice any of these changes:

  • One testicle has gotten noticeably larger or smaller.
  • You have a dull ache in the lower abdomen or groin.
  • You have a feeling of heaviness in the scrotum.
  • You feel pain or discomfort in the scrotum or a testicle.
  • You notice an enlargement or tenderness in your breasts.

Any of these could be a warning sign of cancer or something else, such as an infection. Only your doctor can diagnose what the problem is and decide on the proper treatment. Remember, the earlier a problem is found, whether it's cancer or something else, the more options there are for treating it and the easier it will be to treat.