Testosterone (S-Testo) is a male sex hormone or androgen that is found in both men and women. Testosterone production is controlled by luteinising hormone (S-LH) secreted by the anterior lobe of the pituitary gland. Men produce testosterone in the testes and women in the ovaries but both sexes also produce testosterone in the adrenal gland.
Testosterone affects the growth of the sex glands and external genital organs, body hair, muscle and bone development and deepening of the voice. In addition to physical effects, testosterone affects social and sexual behaviour. Boys start to produce testosterone in the testes during puberty, and development continues throughout life. Production declines in older age, however.
The majority of testosterone is transported in blood, bound to sex hormone binding globulin (SHBG). Only a small amount of testosterone, approximately 1–3% in men and 0.5–1.3% in women, is free in the blood. Because production of testosterone in the testes varies by the time of the day, blood testosterone levels are highest in the morning.
When is a good time to measure testosterone levels?
Testosterone levels in males are measured when it is suspected that not enough testosterone is secreted (hypogonadism). It is also measured when examining the cause of infertility, lack of sexual desire and impotence.
In women, testosterone levels are measured when examining the cause of infertility or ovarian dysfunction or when a tumour that produces too much testosterone is suspected.
Symptoms indicating disturbances in the level of testosterone include:
- Loss of libido
- Erectile dysfunction
- Irregular menstrual periods or amenorrhea (absence of menstruation)
- In women, excessive growth of hair, low voice or balding
- In boys, delayed or slow puberty
- In boys, abnormally early onset of puberty (precocious puberty)
- Impaired concentration
- Sleep disorder
A sensitive testosterone assay (hs-Testo) is recommended especially when the concentration could be low (<2–5 nmol/l). This method is appropriate for checking the testosterone level in women and children and examining hypogonadism (lack of testosterone) in men.
What does a testosterone test measure?
A blood testosterone test is used to measure the total amount of testosterone in blood. If the concentration of testosterone transport proteins in blood changes, the total testosterone concentration changes as well.
How to interpret the testosterone test result?
Normally, the result is:
Reference values, testosterone:
- over 16 y: 0,4-2,0 nmol/l
- 16-60 y: 10-38 nmol/l
- over 60 y: Reference values are not usually reported to older men, but the value usually decreases with age. Hypogonadism usually appears when testosterone is below 10-12 nmol/l and is common when the value is below 7 nmol/l.
Reference values testosterone, sensitive:
- Women: 0,4–2,0 nmol/l
- Men, 16–60 y: 10–38 nmol/l
We also recommend the following tests to check testosterone levels: dehydroepiandrosterone sulphate (S-DHEAS), luteinising hormone (S-LH) and follicle-stimulating hormone (S-FSH).
The reference values of this examination have changed 11.10.2021. You will find your own result's reference values from My LOUNA in touch with the graph.
What can cause elevated testosterone values?
In women, excessive production of testosterone can be caused by the ovaries and/or the adrenal glands. High levels of testosterone can be caused by:
- Polycystic ovary syndrome (PCOS)
- Tumours in the ovaries, adrenal glands or the pituitary gland
- Certain medicines (e.g. contraceptives, antiepileptic drugs, anabolic steroids)
In women, excessive production of testosterone causes increased hair growth and menstrual disorders.
In men, elevated testosterone levels are observed in the following situations:
- In connection with hyperthyroidism (overactive thyroid)
- Tumours in the adrenal glands or the pituitary gland
- In boys, in connection with early puberty
What can cause decreased testosterone values?
In men, low testosterone values can be caused by the following factors:
- Testicular hypofunction (hypogonadism)
- Hypofunction of the pituitary gland (hypopituitarism)
- An extra X chromosome in men (Klinefelter syndrome)
- Late puberty
- Long-term alcohol use and liver cirrhosis
- Strenuous physical stress
- Oestrogen therapy
- Orchiectomy (removal of the testes)
- Down’s syndrome
- Steroid use
The level of SHBG, protein that transports testosterone, increases in connection with hypothyroidism (underactive thyroid). As a result, the level of free testosterone decreases even if the testosterone level is within the reference range.
SYNLAB tests: Testosterone https://www.yml.fi/tuotekuvaus_show.php?tuotenro=342
Terveyskirjasto health library: Testosterone (S-Testo and S-TestoVL) https://www.terveyskirjasto.fi/terveyskirjasto/tk.koti?p_artikkeli=snk04080&p_hakusana=testosteroni Labtests Online: Testosterone Test https://labtestsonline.org.uk/tests/testosterone-test
Fasting is not required
This examination does not require fasting