Testosterone

Testosterone is the most important male sex hormone – but essential for women too. It regulates muscle mass, libido, bone structure, mood and cognitive performance. It is synthesised from DHEA and progesterone. Chronic stress acts on the testosterone level via cortisol.

How testosterone acts in the body

In men, the Leydig cells of the testes produce most of it, controlled by LH from the pituitary; in women, smaller amounts come from the ovaries and adrenal glands. In the blood, testosterone is mostly bound to SHBG and albumin; the free fraction is the active one. In target cells it acts on the androgen receptor or is converted to dihydrotestosterone (DHT) or, by aromatase, to oestradiol. In this way it influences protein building in muscle, bone density, blood formation, sebaceous glands, libido and drive.

Low testosterone – what happens in the body?

When little testosterone is active, muscle builds less protein, fat tends to be stored – preferentially around the abdomen –, bone density decreases and blood formation is stimulated less. Libido, erectile function, drive and mood may decline. Causes include age, excess weight (aromatase in fat tissue converts more testosterone into oestradiol), lack of sleep, ongoing stress, opioids and diseases of the testes or pituitary. In women, low levels are less clearly interpretable.

High testosterone – what happens in the body?

In men, high levels usually result from supplied androgens: the pituitary then reduces LH and FSH, the body's own production and sperm production decline, the number of red blood cells rises and more oestradiol is formed via aromatase. In women, a raised value often shows as increased body hair, blemished skin and irregular cycles; a common cause is polycystic ovary syndrome.

The interpretation is given in your report.