What does testosterone do in the body?
Testosterone is the primary male sex hormone, but also plays a role in women. It drives muscle mass, fat distribution, bone density, libido, and partly also mood and energy. In men, it is produced mainly in the testes; in women, in the ovaries and adrenal glands.
In men, levels decline gradually with age, on average around one to two per cent per year from the age of thirty. This is normal and proceeds without noticeable symptoms in most men. A level that is notably low for one's age, or that is falling faster than expected, is a different matter.
Complaints that people associate with low testosterone
The classic complaints are fatigue, reduced libido, loss of muscle mass, and mood problems. But virtually all of these complaints are non-specific: they can have dozens of other causes. Sleep deprivation, thyroid problems, low iron, chronic stress, all of these can produce the same symptoms as a low testosterone level.
What does a testosterone test measure?
Total testosterone in the blood is the most commonly measured. But testosterone is partly bound to proteins in the blood, only free testosterone is biologically active. SHBG (sex hormone-binding globulin) largely determines how much testosterone is freely available. In a complete hormone panel, both are measured, alongside LH and FSH (hormones from the brain that drive production) and oestradiol.
The time of the blood draw matters: testosterone is at its highest early in the morning. A measurement later in the day can give a lower value without there being a deficiency. Bloodworks recommends a morning blood draw for the most representative measurement.
Want to have your hormone values measured?
The Essential Hormones Male package measures testosterone, LH, FSH, SHBG, oestradiol, and prolactin in a single blood draw.
In women: testosterone as part of the hormonal picture
Women can also experience symptoms from a low testosterone level, reduced libido, fatigue, muscle loss. Measuring testosterone in women has a different reference frame than in men. The female hormone panel typically combines testosterone with oestradiol, progesterone, LH, FSH, and prolactin, together these give a complete picture of hormonal balance.