What is Testosterone and Why is it Important?

Testosterone is a hormone that is produced by your body. It has traditionally been thought of as the male sex-hormone, however, women also need testosterone, admittedly lower levels, but it is nonetheless important in both sexes.  Hormones are chemical messengers that signal target organs to help them function properly.

In men, testosterone is predominantly produced by the testes, it is produced in response to signalling from the pituitary gland. Testosterone is broken down in part by the aromatase enzyme located in the testes, brain, skin, bone and liver is there is dysfunction. This enzyme converts testosterone to oestradiol. This has a negative feedback on the Hypothalamus and Pituitary gland (HPG) which forms part of the Hypo-pituitary Gland axis that controls production of testosterone.

Oestrogen has a negative feedback on the brain, suppressing the release of Lutenising Hormone (LH) from the pituitary gland, preventing stimulation of the Leydig cells of the testes and subsequent production of testosterone by these cells.

Testosterone is also broken down in part to Dihydrotestosterone (DHT) by the enzyme 5-alpha reductase located in the testes and prostate. This hormone is responsible for sexual differentiation, secondary sexual body hair, libido, muscle growth, prostate health.

Testosterone has long been thought of as simply the male sex-hormone, its role and function within the body is of far more significance. It is integral for long term physical and psychological health. In fact, its relationship and role in facilitating function is far more complex. The ratio of free testosterone to oestradiol to dihydrotestosterone is of greater significance than absolute numbers of the individual hormones.

Testosterone, Oestradiol and Dihydrotestosterone affect the following organs –

  • Brain – mood, cognition, sex-drive / libido, sense of well-being.
  • Cardiovascular system – arterial elasticity and wall thickness, blood pressure.
  • Muscle – muscle mass.
  • Sexual Organs – erectile function, prostate health, morning erections / nocturnal penile tumescence.
  • Bone – bone strength.
  • Liver – liver function and decreased inflammation.
  • Adipose tissue – lipid function, visceral fat mass.
  • insulin sensitivity and insulin resistance.

As you can see, testosterone, oestrogen and dihydrotestosterone have important roles within the human body.  Testosterone, oestradiol and dihydrotestosterone are anabolic hormones, their primary role is to help facilitate growth and repair.  Testosterone is primarily produced at night, whilst asleep, hence levels being highest early morning.  However, these hormones are necessary 24 hours a day to help support the body and combat the effects of catabolic processes that predominate when active.

All hormones are dependent, whether that be a direct relationship like the thyroid and HPG axis or indirect, they are not independent. The body likes stability, the body likes hormonal balance.  There are complex physiological mechanisms maintaining a constant internal environment despite external changes. Help your body achieve homeostasis, hormonal balance is necessary for health. Testosterone, Oestradiol and Dihydrotestosterone are just as important as every other hormone involved in keeping your body healthy, time to take a stand.

Testosterone Deficiency & Diagnosis

Dr Robert Stevens MBChB MRCGP Dip.FIPT