Testosterone (S-Testo and S-TestoVl)
Testosterone is the main male sex hormone produced by the testicles. Before puberty, boys have as little testosterone as girls. The testicles start producing testosterone at puberty, and it continues throughout life. However, in older people, secretion gradually decreases so that at least one-third of men over 75 have a lower than normal amount of testosterone in their blood ( Testosterone in aging men ). In women, small amounts of testosterone are produced in the ovaries and in the epididymal layer, which is why they also have small amounts of it in their blood.
Testicular testosterone production varies depending on the time of day. The blood testosterone level is at its highest in the morning. The reference values are defined according to the morning values, so the blood sample for testosterone measurement should be taken in the morning before 10 a.m. The result measured from the blood sample taken in the afternoon may be below the reference values, even if there is no disturbance in testosterone production.
In the blood, most of the testosterone is bound to plasma proteins and only 1–3 percent is free in the plasma aqueous solution. The S-Testo test measures the amount of total testosterone in the blood. If the concentrations of hormone-binding proteins in the blood change, the S-Testo value also changes, even if testosterone production is normal. If it is suspected that the concentration of plasma proteins has changed, a more complex and expensive free testosterone assay, S-TestoVl, can be used. In the abbreviation, Vl stands for "free calculated". The concentration of free testosterone is calculated based on a specific formula after the concentrations of total testosterone and the main testosterone-binding proteins have been determined. Some laboratories use direct methods to measure free testosterone (S-TestoV),
Testosterone deficiency is caused by the testicles not being able to produce enough of it. Any disease that affects the testicles can lead to it. These include, for example, an undescended testicle (see testicular problems in boys ), testicular infections, and testicular cancer. The congenital sex chromosome disorder Klinefelter's syndrome is associated with reduced testosterone production. Disorders of the pituitary gland can also cause a lack of testosterone because the testicles need regulation from the pituitary gland in order to produce testosterone appropriately.
A lack of testosterone in childhood results in the normal male changes of puberty not occurring. If the disorder appears after puberty, it can cause sexual reluctance, erectile dysfunction, breast growth in men (gynecomastia), decreased sperm production, and infertility. Long-term deficiency can lead to hair loss, muscle weakness, and osteoporosis, i.e. bone loss.
Anabolic steroids have similar effects to testosterone, as a result of which they interfere with the regulation of testosterone production so that its production can decrease or stop. Gaining weight and heavy alcohol consumption also reduce testosterone levels.
In aging men, the decline in testosterone production can be accompanied by various general symptoms, such as fatigue, decreased ability to concentrate, sleep disorders, and sexual desire (see Testosterone in aging men ). Similar symptoms occur for other reasons as well, and testosterone therapy is not a universal treatment for them. If, in addition to the symptoms, a clearly reduced testosterone concentration in the blood is found (below 8 nmol/l measured several times), testosterone preparation can be tried as a treatment.
Testosterone deficiency can be effectively corrected with testosterone therapy, which uses long-lasting medicinal preparations injected into the muscle or a gel administered daily to the skin. The adequacy of the medication dose is monitored using blood testosterone measurements.
Overproduction of Testosterone
Women sometimes experience an overproduction of testosterone, which can result in excessive hair growth and menstrual disorders. Testosterone levels in the blood are usually measured in connection with studies of excessive hair growth and polycystic ovary syndrome (PCOS) . At the same time, other hormones produced by the adrenal gland are studied, which have androgenic, i.e. testosterone-like, effects. In men, increased values can be associated with some diseases, tumors, or excessive use of testosterone.