Testicles and Why Their Size Matters

The testes, or testicles, are part of the human male’s reproductive system. There are two main types of cells found within the testicles: germ cells and Leydig cells.

A germ cell is a reproductive cell, in this case a sperm cell. Each mature germ cell contains a single set of 23 chromosomes containing half the usual amount of DNA found in a human and half the number of genes found in a human because the egg germ cell contains the other half. When the egg and the sperm cell join to form a fertilized cell the full set of DNA is thus created.

Leydig cells are found adjacent to the seminiferous tubules in the tesicles. Leydig cells produce steroids, including the androgens testosterone and dihydrotestosterone (DHT) which play a vital role in male fertility. Testosterone is thought to help regulate sex drive or libido, bone mass, fat distribution and muscle mass.

Healthy males produce germ and Leydig cells in equal proportion, which gives the testicles their roundness, firmness and fullness. Most human testicles are egg-shaped. The testes work best at temperatures slightly cooler than the rest of the body. Sudden temperature changes can cause the testicles to shrink up into the body or fall away from the body.

One testicle is usually smaller than the other, which is the same scenario for female breasts. One testicle typically hangs lower than the other as well. This is normal in terms of anatomy.

Testicles in human males develop over time. During infancy, testicles are at their smallest in size. At the on-set of puberty, the testes begin to grow as they develop, ultimately taking on their final shape and size in early adulthood. Testicle size is important because cases in which the gonads cease to grow or in which they undergo shrinkage can signify ill health in the affected male.

For example, testicular atrophy is a pathological condition, which results from unknown causes, in which there is abnormal shrinkage of the testicles. Most cases of testicular atrophy are linked with hormonal imbalances, recreational drug use, increasing age, any injury to the testicular area and diseases such as Mumps and HIV. Men with the condition experience decreased libido and sometimes infertility.

Men with testicular atrophy are not producing germ and Leydig cells in proportion within their testicles. One or both of the cell types start to die, causing extremely shrunken testicles that are very soft in feel and loose-looking.

At the on-set of puberty, health care professionals measure the testicles to track the progress of puberty. There are several ways to measure testicles. One method is to use a soft measuring tape or a pair of calipers to measure the length, width and depth of the testicles. The volume of the testes can then be calculated using these three measurements to determine the size of the testicles.

Another method of measuring the size of testicles uses a medical instrument called an orchidometer, which was created by Dr. Andrea Prader (1919-2001) in 1966. Dr. Prader was a Swiss pediatrician and professor of endocrinology. An orchidometer is a series of strung-together beads made from either wood or glass that range in size from 1 milliliter (mL) to 25 milliliters. Orchidometers are used all over the world today.

A health care professional will place the beads on the orchidometer next to a testicle to find the bead that is closest to the size of the testicle in question. This gives a known measurement of volume. Prepubescent boys are measured with beads ranging from 1 to 3 mL in size. Pubertal males, who are experiencing the stages of puberty, are measured with beads starting at 4 mL in size. Adult males are measured using beads representing 12 to 25 mL in size.

All boys should have their testicular size checked routinely from the time of birth so that any abnormalities or changes in the testes can be quickly addressed. Discrepancies in testicular size combined with other signs of maturation can help medical professionals diagnose such diseases as hypogonadism, or interrupted puberty.

A diagnosis of macroorchidism, or large testes, in young males is one sign of the inherited generalized learning disability called fragile X syndrome, which is also known as Martin-Bell syndrome. In South American countries, this condition is more commonly called Escalante’s syndrome. No matter what name is used to describe the syndrome, the condition is a result of a genetic mutation in a DNA sequence. Large testes are just one result of this genetic mutation.

One symptom of testicular cancer is irregular size of the testicles. This is why it is important for adult males and their partners to pay attention to the size and shape of the testicles.

From a health perspective, size of the testes really does matter. Guys, get those testicles measured or examined on a regular basis and reach out to a health care professional if there is any visible shrinkage or enlargement of the testes.


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