Testosterone is the principal male sex hormone, and is required for sperm production, development of male reproductive organs and appearance of secondary male sexual characteristics. SHBG is a transporter protein that binds to sex hormones such as testosterone in the bloodstream. Only a small fraction of circulating testosterone is free (and therefore biologically active), as the majority is bound to SHBG and therefore inactive. When measuring testosterone concentrations in the blood, ‘free’ testosterone is calculated from total testosterone and SHBG levels.
Food for more testosterone
Nutrients work hand in hand with hormones like testosterone to build muscle. But if you've been following the traditional, outdated advice for losing weight—cut calories, reduce dietary fat, and watch your intake of red meat and eggs—you are missing out on those critical nutrients that build T levels and foster "anabolism," or muscle growth. If you want to lose 20 pounds of fat, build major muscle, and boost your testosterone, pair your workouts with these food rules from sports nutritionist Tara Gidus, ., team dietitian for the NBA's Orlando Magic.