Testicles FAQ

Medically Reviewed by Dan Brennan, MD on October 15, 2019

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 and store 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.

When will my testicles begin to grow?

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.

How big are testicles?

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

Is it normal to have one testicle that's bigger than the other?

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.

Why do my testicles shrink when I get cold?

For your testicles to produce sperm, they must be kept at just the right temperature. As a result, 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.

Why do my testicles hang down?

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 testicles will become larger and more floppy to release extra heat.

What if I have painful or swollen testicles?

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.

Could I have testicular cancer?

Testicular cancer occurs when cells in the testicle divide abnormally and form a tumor. 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

You should consider examining your testicles on a monthly basis and check for lumps. When examining the testicles, cup them with your hand and gently rub one testicle at a time between your thumb and pointer finger. Your testicles should feel oval and smooth. If you notice a hard lump, get checked by a doctor.

Keep in mind, the scrotum has other parts to it besides the testicles. You may 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.

WebMD Medical Reference



Nemours Foundation: "Male Reproductive System."

Nemours Foundation: "Is It Normal for One Testicle to Be Bigger?"

American Academy of Pediatrics: "Physical Development in Boys: What to Expect."

American Academy of Pediatrics: "Boys' Secondary Sex Characteristics."

Great Ormond Street Hospital: "Hanging Testicles."

American Cancer Society: "Do I Have Testicular Cancer?"

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