A biomarker is a molecule that can be found in bodily tissues, blood, and other fluids. These molecules are often examined by medical professionals when seeking to diagnose conditions, diseases, or abnormal processes. Before undertaking Testosterone Replacement Therapy (TRT), biomarkers are measured to gauge whether someone might be experiencing low levels of testosterone.

Testosterone – a hormone primarily produced in the gonads (testicles or ovaries). For men, it helps to regulate sex drive and has a role in controlling bone mass, fat distribution, muscle mass, strength and the production of sperm and red blood cells. Testosterone levels in men naturally decline after the age of 30, although lower than normal levels can occur at any age, resulting in low libido, erectile dysfunction, difficulty in gaining and maintaining muscle mass and lack of energy.

Free Testosterone – most testosterone circulating in the blood is bound to proteins, in particular SHBG and albumin, although a small amount (only 2-3 %) of testosterone is free and available to cells.

Albumin – a protein made mainly in the liver which helps hold water within the blood. This is important for tissue growth and repair, as it helps carry nutrients, medications, and other substances through the blood. Albumin also carries hormones around the body. Therefore, measuring the amount of albumin in the blood can help us calculate how much hormone is available to your tissues.

SHBG (sex hormone binding globulin) – a protein which transports the sex hormones (testosterone, oestrogen and dihydrotestosterone) in the blood. Hormones which are bound to SHBG are inactive, meaning they are unavailable to your cells. Measuring the level of SHBG in your blood gives important information about the amount of unbound hormones that are biologically active and available for use.