Testosterone is the primary male sex hormone, but it's also produced in smaller amounts in females.
It's responsible for the development of male reproductive tissues, muscle mass, bone density, and body hair.
Furthermore, testosterone plays a significant role in the synthesis of protein, fat distribution, and the production of red blood cells.
The hormone exists in two states in the blood:
- Bound testosterone: This is testosterone that's attached to proteins (mainly sex hormone-binding globulin (SHBG) and albumin).
- Free testosterone: This is testosterone that isn't bound to proteins and is available for the body to use.
Free testosterone is especially crucial as it is the bioactive form, meaning it's available to affect various processes within the body, including muscle growth.