The body uses hormones to trigger necessary changes in physiological processes and behaviour. You can think of them as chemical messengers, travelling through the bloodstream to different organs and delivering instructions. One such hormone is testosterone. Since testosterone is the primary sex hormones in males, you probably already know a lot about it. In this article, we’ll take a closer look at what it is and what it does.
Most of the testosterone in a man’s body is produced by specialized cells called Leydig cells located in the testicles. These cells synthesize it out of cholesterol when stimulated by another hormone called LH or luteinizing hormone. To better understand this process, you need to know more about the hypothalamic-pituitary-gonadal axis.
As the name suggests, this axis is formed by the hypothalamus, the pituitary gland and the gonads. The gonads are the primary reproductive organs meaning ovaries for women and testicles for men. The hypothalamus is located on the undersurface of the brain, above the midbrain. It’s an extremely complex structure with many important functions like regulating body temperature, sleep, appetite, weight, and emotions. One of its functions is to regulate the endocrine system in conjunction with the pituitary gland located just below it. The pituitary gland is the master endocrine gland that produces hormones involved in many vital bodily functions.
In the case of testosterone production, the hypothalamus sends a chemical signal to the pituitary gland in the form of the gonadotropin-releasing hormone or GnRH. In response, the pituitary gland produces luteinizing hormone or LH. The LH travels through the bloodstream and reaches the testicles where it signals the Leydig cells to produce testosterone. This axis forms a feedback loop which ensures optimal levels of testosterone. The hypothalamus can sense if there is too much testosterone in the blood and can reduce production by communicating with the pituitary gland.
The adrenal glands located right on top of the kidneys can also produce testosterone but in much smaller quantities.
As the primary sex hormone in males, testosterone is involved in the development of male sexual characteristics, which include:
- Development of the testicles and penis
- Production of sperm
- Sex drive
- Growing body hair
- Stimulating the larynx to grow and the vocal cords to lengthen and thicken during puberty which is why men develop thicker voices and why they have what’s called Adam’s apple. The Adam’s apple is a lump of cartilage that protects the larynx. Since men have bigger larynges, they stick out.
- Growing and maintaining muscles and muscle strength
- Bone gain and maintenance
At about 8 weeks after conception, the male fetus starts producing testosterone which helps the process of masculinization of the genital tissue. As boys go through puberty, their testosterone production increases significantly – about 30-fold. Levels reach their peak around the age of 18 or 19 and plateau until the age of 30 when they start to decrease by an average of 1% per year.
Teenage boys whose bodies are unable to produce the required levels of testosterone might not experience this normal phase of masculinization so their genitals might not enlarge, their voices might not become deeper, and they might grow less body hair than average.
Because testosterone is critical for sperm production, insufficient levels can also lead to infertility.
Furthermore, testosterone can influence emotions, mood and behaviour, as well as other functions. Research is ongoing on the complex role of this hormone in the human body.
Testosterone is also important for women. Women produce testosterone mostly though their ovaries and, like men, can make smaller quantities through their adrenal glands. A balance of estrogen and androgens like testosterone is necessary for the ovaries to function optimally.
Common Side Effects of Low Testosterone
The human body can usually produce all the testosterone it needs since it has a mechanism to regulate it. However, some people can have unnaturally low levels which results in hypogonadism. To determine if a person’s testosterone levels are too low, they will need to do at least two blood tests to measure it.
Testosterone levels can vary a lot, but they tend to be highest in the morning, so these tests are usually performed between 7 AM and 10 AM. The tests will be performed on different days to confirm the results. If both tests indicate low levels of testosterone, your doctor will need to do further investigations to determine the cause of the deficiency.
Men with hypogonadism can benefit from testosterone replacement therapy or TRT. If you think you might have low testosterone, you can make an appointment with your doctor to get tested and read more about treatment options on sites like Balance My Hormones. Like any medical treatment, TRT can lead to side-effects, so it’s not appropriate for men with normal testosterone levels for their age.
Low levels of testosterone can stem from problems that affect the testicles or the rest of the hypothalamic-pituitary-gonadal axis. The term primary hypogonadism refers to hypogonadism that stems from problems related to the testicles that might have been damaged by injuries, infection, tumours, chemotherapy or radiation therapy.
Secondary hypogonadism is the term used for hypogonadism originating from the hypothalamus or pituitary gland. The causes can be infections, tumours and certain medications.
Some cases of hypogonadism are caused by genetic disorders like Klinefelter syndrome, Prader-Willi syndrome, Kallmann syndrome, myotonic dystrophy and hemochromatosis.
Chronic diseases that can reduce testosterone production are obesity, type 2 diabetes, kidney and liver disease and autoimmune conditions.
Symptoms of low testosterone include:
- Difficulty building and maintaining muscle mass as well as the loss of muscle mass
- Osteoporosis
- Low libido
- Erectile dysfunction
- Low sperm count and infertility
- Lack of or loss of body hair
- Small testicles
- Growth of breast tissue that may cause soreness
- Fatigue
- Trouble concentrating
- Irritability
- Depression
Scientists and pharmaceuticals companies are still researching the impact testosterone deficiency has on the male body. Since testosterone production declines with age, about 1 in 3 men above 45 have suboptimal levels. Having said that, determining what is optimal is difficult and controversial since levels vary by a lot.
Since, as we mentioned before, testosterone also plays an essential role in women’s health, they can also develop symptoms as a result of a deficiency. This includes reduced bone strength, poor concentration and low libido. The decline can be caused either by menopause and ageing or by a medical condition linked to the ovaries, pituitary gland or adrenal glands.