Why is testosterone so essential for men’s health? How does it work?

Testosterone is the best-known male hormone. It is responsible for the features that turn men into men, such as a deep voice, facial hair, and broader shoulders. But, in fact, that’s just a fraction of what this hormone does. It is important to note that testosterone is also produced in women although it makes only a small percentage of the hormones in female body.

But before we go further into the details of testosterone, let’s define what a hormone is. A hormone is a molecule that is used for physiological signaling. Hormones and the glands that produce them form the endocrine system.

Testosterone is one of the steroid hormones. Steroid hormones are made from cholesterol and have a similar basic structure. The other hormones in this category include estrogen and progesterone.

The Production of Testosterone

Testosterone in males is largely produced in the testicles. The adrenal glands also produce a small amount of the male hormone.

The production of testosterone occurs in an intricate feedback mechanism. For production to be initiated, a part of the brain known as the hypothalamus has to detect low levels of the hormone circulating in blood. The hypothalamus releases a hormone known as the gonadotropin releasing hormone (GnRH). This hormone acts on the pituitary which is located near the underside of the brain. The GnRH stimulates the pituitary gland to release two hormones which act on the gonads− the follicle stimulating hormone (FSH) and luteinizing hormone (LH).

LH stimulates production of testosterone by the Leydig cells. On the other hand, FSH stimulates sperm production by the Sertoli cells in the testicles.

When enough levels of testosterone are detected in the blood, the hypothalamus signals the pituitary to reduce its production of luteinizing hormone and the process is slowed down.

Not all the testosterone produced is available for use in the body. Most of it is bound to proteins in the blood. Most of the testosterone is bound to sex hormone binding globulin and albumin.

The production of testosterone is high in adolescence and it starts to reduce when one approaches 40 years. The levels drop by about 1% every year. By the time a man reaches his 70s, the levels can be very low and this manifests as signs and symptoms of testosterone deficiency.

The Functions of Testosterone

Besides being ‘the male hormone’, testosterone has a wide range of other functions including anabolic and androgenic. The anabolic functions are the ones that involve growth and development. Androgenic functions are primarily those that enhance and maintain the male characteristics of the human body.

Testosterone becomes essential from the earliest days of development – even before the baby is born, in fact. The hormone is responsible for the formation of the penis and testicles when the fetus is in the womb. In the first trimester, testosterone triggers the formation of the phallic urethra, rugation of the scrotal skin, appearance of the prostate and seminal vesicles. In the second trimester, testosterone is responsible for sex formation. The feminization or masculinization of the fetus is determined by the presence of the anti-Mullerian hormone. Testosterone plays a role in masculinization by causing growth of the Wolffian duct which forms the internal male genitalia. Years later, when a boy reaches puberty, the testosterone levels surge and cause further growth of the genitals.

Men with low levels of testosterone are more likely to suffer from erectile dysfunction. On the contrary, those with high testosterone frequently have increased libido. It is also worth noting that when one is sexually excited, testosterone production is temporarily increased to keep the process going. This is a universal process that takes place in all men regardless of their testosterone levels.

At puberty, testosterone also stimulates the growth of hair on the face, arms, chest, legs, in armpits and pubic region. People with low testosterone usually have less body hair but, surprisingly, they are less likely to suffer from male pattern baldness than those with high testosterone. Together with growth hormones, testosterone causes maturation of bone and fusion of the growth plates which results in termination of growth.

The male hormone has also been shown to have an influence on different psychological functions. It is responsible for dominance and self-esteem. It has also been shown to play a role in aggression and competitiveness. People who have low testosterone often struggle with a low mood and blunted affect. What’s more, testosterone has a role to play in cognition. People with the right amount of this hormone have exhibited better memory and mathematical ability in study models.

Several studies have shown that testosterone is important for the growth of muscle bulk. One study in USA analyzed the effect of a topical formulation of testosterone. The participants had their intrinsic testosterone levels suppressed and then they got different doses of the hormone administered as a gel. Those who received lower doses were found to have leaner muscles and lower strength levels. Testosterone promotes muscle growth by interacting with receptors in the DNA to increase the production of certain proteins. Testosterone also helps in the development of muscle by stimulating the production of growth hormone which is directly involved in increasing tissue mass.

The male hormone plays a significant role in the metabolism of fats. It helps in mobilization of the fat stores so that they are consumed more effectively. Men with low testosterone levels can have increased body fat.

Bone mass is partly influenced by testosterone. The hormone ensures mineralization of bone which results in increased bone density. It has been observed that people with low testosterone levels are more likely to have bone fractures, even upon relatively minor impact.

It has also been suggested that testosterone has an immune function of some sort too. This is because the levels of testosterone have been found to be low in people with inflammatory markers in their blood.

Finally, testosterone influences the circulatory system as well – in particular, by promoting the formation of red blood cells in the bone marrow. This leads to improved blood circulation and better nourishment of tissues. However, high testosterone may affect the circulatory system in negative ways too. It has been shown that this hormone influences platelet aggregation which causes clotting.

How Testosterone Works

Testosterone exhibits its effects either directly or after being converted to a more active form called dihydrotestosterone (DHT). Free testosterone is the bioavailable form that can be transported by the body straight to the target tissue. An enzyme in the cytoplasm called 5 alpha reductase is responsible for converting testosterone to DHT, which binds to the same receptors as testosterone but is about five times more powerful.

After binding, the complex formed by the hormone and its receptor undergoes a change in structure and then moves to the nucleus where it attaches to a specific sequence of nucleotides on DNA. This attachment causes androgenic effects by triggering transcription of the target genes.

The testosterone hormone receptors are found in many body tissues. The responses produced depend on the type of tissue receptor activated.

The importance of testosterone in men cannot be underestimated because many patients are showing positive changes with testosterone replacement therapy. As men age, their testosterone levels decline and this has been associated with a number of undesirable symptoms, such as irritability, depression, reduced libido, lethargy, weight gain and thinner bones. The normal level of testosterone ranges from 200 to 1000 ng/ dL and the average is about 600ng/dL. Most people are prescribed replacement therapy when the levels are around 300ng/dL. At this level, most of the signs of deficiency start showing.

It is good to remember that testosterone has its effects on many parts of the body. However, in performing most of these functions, the hormone works together with other hormones and other biological components. Therefore, it doesn’t necessarily mean that you have low testosterone when you exhibit some sort of deficiency.

In a nutshell, testosterone is more than just the male hormone. It makes a man complete because it is involved in so many processes that ensure one’s health and wellbeing.

author: Dr. Marian Davis

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