Testosterone is an androgen, the male hormone produced predominantly in the testes, which is responsible for many of the male sex characteristics. Women also produce small amounts of testosterone in the ovaries and adrenal glands.
Free testosterone refers to the amount of the hormone which is not bound to either albumin or sex hormone binding globulin. 
Testosterone levels can be indicative of various conditions in both males and females. Testosterone levels in men naturally fall as they age, leading to symptoms such as reduced sex drive and erectile dysfunction. Abnormal levels in women can cause conditions like polycystic ovary syndrome (PCOS).
A testosterone test is usually used if you suspect your levels may be too high or too low. As a result, you may display some unpleasant and uncomfortable symptoms.
You can test your testosterone levels along with other key fertility hormones by purchasing a simple at-home finger prick test kit which is then analysed at an accredited lab. Forth offers a number of blood tests which include testosterone such Female Fertility, Male Hormones, Menopause Health and our Vitality package which includes analysis of over 30 key biomarkers for good health.
Testosterone has important roles in the human body affecting several organs as well as our sexual development and function.
In men, the secretion of testosterone follows the circadian rhythm, so their levels are highest in the early hours of the morning. In early adulthood, testosterone is required for the growth and regulation of the prostate gland. Prostatic cell growth occurs because testosterone travels via the blood to the prostate gland where it is converted to dihydrotestosterone. 
Testosterone is responsible for the development of the male reproductive organs and system. The hormone is also essential for the development of sperm in adulthood. As boys mature during puberty, testosterone is associated with:
Testosterone also regulates the secretion of other hormones like luteinising hormone and follicle stimulating hormone.
In women, the production of testosterone in the ovaries and adrenal glands is usually converted to oestradiol, a type of oestrogen.
The levels between men and women differ greatly. Men, on average, have 10 times more testosterone than women.
Increases in testosterone in women and decreases in men can negatively affect our health and wellbeing,
Naturally, as men age, their testosterone levels fall which can cause various symptoms and effects. The normal levels of testosterone in men are:
In females, increased levels of free testosterone can cause polycystic ovary syndrome (PCOS). PCOS causes the loss of periods as well as some unpleasant symptoms.
If you are worried about your testosterone level or just want to check where you fall on the range, you can test your level with a simple at-home blood test.
Polycystic ovary syndrome affects the function of the ovaries and causes unwanted side effects. Tumours in the adrenal gland or ovary are also responsible for increases in female testosterone levels.
A decreased circulating testosterone and SHBG level are risk factors for metabolic syndrome in elderly men. Metabolic syndrome is the name given to a combination of diabetes, high blood pressure and obesity. Metabolic syndrome increases the risk of coronary heart disease, stroke and cardiovascular disease.
A male’s testosterone level may fall because of damage to the testes, alcoholism or viruses like mumps.
Symptoms of PCOS include:
PCOS affects 1 in 5 women who are of reproductive age and can have some psychological side effects, like:
The symptoms of metabolic syndrome are:
Metabolic syndrome is diagnosed if you have at least 3 of these symptoms.
Testosterone levels gradually fall as men age, usually at a rate of approximately 2% each year from the age of 30 or 40. As a result, there may be symptoms such as:
Because testosterone has major roles in the growth and maintenance of muscle and bone, it is an important hormone with regards to exercise and physical training. Studies have shown higher intensity exercise cause higher levels of testosterone in the body. 
Diet and lifestyle choices can help to treat and control both PCOS and metabolic syndrome. Heart disease and diabetes are side effects of PCOS, as well as major factors in SHBG and so eating the right diet is key to preventing them. Eating a diet with low glycaemic index foods can be beneficial. Low GI foods raise blood sugar slowly which reduces the symptoms of PCOS and they help to manage diabetes.
Low glycaemic foods include:
Low GI foods are particularly useful in conditions which make individuals resistant to insulin. 
Being overweight is a risk factor for both metabolic disease and PCOS and increases the severity of these conditions. Physical activity is beneficial for weight loss but also improves the body’s response to insulin.
As men increase in age their levels of testosterone levels reduce. Men in their 70s have approximately 40% less testosterone than men in 20s. The reduced testosterone level is associated with a lower quality of life as well as reduced muscle mass and an increased risk of osteoporosis. In middle-aged men, who take part in moderate to vigorous exercise, greater improvements in testosterone levels also improve cardiopulmonary fitness.  Supplementing your diet with calcium and vitamin D is a good way to maintain strong bones and teeth, although you should be able to get your reference nutrient intake by eating a healthy balanced diet.
Low testosterone can affect libido, mood and muscle mass. Check your level with a simple at-home finger prick test.
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 Chubb, S, A, P et al. (2008). Lower Sex Hormone-Binding Globulin is More Strongly Associated with Metabolic Syndrome than Lower Total Testosterone in Older Men: The Health in Men Study. European Journal of Endocrinology: 158(6).
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 Hawkin, V, H., Foster-Schubert, K and Chubak, J et al. (2008). Effect of Exercise of Serum Sex Hormones in Men: A 12 Month Randomized Clinical Trial. Med Sci Sports Exerc: 40(2), pp 223-233.
 NHS. (2019). Prevention Osteoporosis. Available at: https://www.nhs.uk/conditions/osteoporosis/prevention/