What is the connection between testosterone and hair growth?

Testosterone is a steroid hormone that is included in a group of special hormones called androgens. Found in both males in females, testosterone is produced by the testicles in males and the ovaries in females. Adrenal glands also produce the said hormone, but only in small amounts.

Testosterone is often regarded as the primary male sex hormone, and it plays an essential role in the development of the testis and prostate, which are the organs found in the male reproductive system. The hormone is also responsible for various bodily changes we undergo during our adolescent years, and some of these changes are related to sexual maturation. The noticeable change in our bodies, such as the deepening of our voice, the growth of body hair, and the development of interest in sexual intercourse are all triggered by testosterone.

In the years where we experience puberty, the body starts to produce more androgens, although it creates more testosterone than any other androgens. The newly produced testosterone then circulates around the body and will get attached to the androgen receptors found in the hair follicles. To understand how our hair gets longer, we must enumerate the three phases of its growth.

The first phase is called anagen (the active growth stage), the second is catagen (the transitional stage), and the last phase is the telogen (the dying stage). This cycle of hair growth repeats itself throughout our lifetimes, which is the reason why our hair continues to grow. In the case of body hair, particularly in the arms, chest, and legs, the telogen phase is longer than the anagen phase, as opposed to scalp hair, where the anagen phase is the longest. The shorter telogen phase in scalp hair allows each strand to grow longer without dying, and the longer telogen phase in body hair makes our arm or legs hair much shorter.

There are two types of hair in our bodies, and these are called vellus and terminal. Vellus hair is finer and lighter than terminal hair, which allows it to have less visibility. On the other hand, terminal hair is darker, thicker, and more visible. 

Both of these types of hair cover the human body starting from birth. Hair follicles are sensitive to androgens, and the sensitivity level depends on the genes. Since hair follicles are sensitive to androgens like testosterone, the rising levels of hormones in the body during puberty causes the formation of thick hair. In turn, the androgens would transform vellus hair to terminal hair. However, as previously mentioned, the transformation depends on the sensitivity of the hair follicles to the androgens, so thick hair doesn’t usually appear for some people. Normally, pubic hair is the first to appear for both men and women. Since androgenic levels in men are about seven times more than females, the males tend to have more body hair. The distribution of androgenic hair throughout the body largely depends on the follicles’ sensitivity to testosterone and other androgens.

As people enter their middle or mid-life age, the terminal hair follicles may start to revert into vellus follicles, which means that the hair will become thinner and weaker. Though scientists have no clear explanation about it, hair loss is supposed to be caused by the decreasing circulation of hormones in the body. The lack of hormones results in the slow death of hair follicles as well as the reduction in body hair.

Does Testosterone Have Other Functions?

Besides hair growth, testosterone is also responsible for the maturation of several organs in our body. For one, testosterone allows our bones to grow, and in turn, it also enables us to have growth spurts before puberty. Furthermore, bone growth increases the chances of the bones in the person’s jaw, chin, nose, and eyebrows to remodel itself into a form that would fit an adult. Along with bone changes, the muscle mass in the body also increases along with the broadening of the shoulders.

One of the most notable changes done by the testosterone is the Adam’s apple, which is a feature found at the front of the neck that serves little to no purpose other than to show that the male has experienced puberty. Testosterone is also responsible for the enlargement of the sebaceous glands that causes acne. The rise of testosterone levels in puberty is the reason for the common belief that the sign of being a teenager is having too many pimples or acne on the face.

Once the testosterone level normalized after puberty, the hormone will then focus on the development of sperm cells, as well as the enlargement of the penis for males and the clitoris for females in the reproductive system. Testosterone also normalizes muscle growth for adults, along with the other androgens that serve to keep the body healthy. Although the functions of the testosterone are more evident in males, both sexes need the hormone for proper cell growth.

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