The SHBG gene is one of the genes used in combination to determine your testosterone levels. Sex-hormone binding gobulin (SHBG) levels are regulated through this gene. This protein is involved in the transport of sex hormones which is how it can influence the levels of circulating testosterone. The TT genotype is extremely rare, with it not found within the majority of populations.
Source: 1000 Genome Project. Global averages for both sexes
Sex hormones, which are steroid hormones, are chemicals that produce a variety of effects on the body. In women, the primary sex hormone is oestrogen, whereas in men it is testosterone. However, both hormones are present in males as well as females. Some of the most important outcomes of sex hormone actions are the determination of primary and secondary sexual characteristics, the effects of which become increasingly apparent at the onset of adolescence.
In addition, sex hormones are also responsible for controlling a number of metabolic effects that are essential for cellular homeostasis, including coordination of fat storage and protein synthesis. To this end, testosterone is a key driver of lean muscle growth and high free circulating levels of testosterone correlates with good muscle gain. We look at common variants in several genes that have recently been shown to influence levels of hormones such as testosterone in the bloodstream.