SHBG Explained: Why Your Free T Matters More

What SHBG Does

Sex hormone-binding globulin is a transport protein produced by your liver that binds to testosterone with high affinity, effectively locking it away from your tissues. Think of SHBG as a safety deposit box for your testosterone. The testosterone inside is counted in your total, but your body cannot access it. Only the testosterone that is free or loosely bound to albumin is available for biological activity.

This is why SHBG is one of the most important and most overlooked markers in men is hormone health. A man with total testosterone of 600 and SHBG of 20 has far more bioavailable testosterone than a man with total testosterone of 600 and SHBG of 60. Same total, completely different clinical picture.

High SHBG Causes

SHBG rises with aging, hyperthyroidism, liver disease, certain medications including anticonvulsants, low body weight, and excessive endurance exercise. High SHBG is one of the most common reasons men have symptoms of low testosterone despite normal total levels. It creates a functional deficiency where the number on your lab report looks adequate but your body is operating with a deficit.

Low SHBG Causes

SHBG decreases with obesity, insulin resistance, hypothyroidism, high-dose androgen use, and corticosteroid use. Very low SHBG can artificially inflate free testosterone calculations while also causing rapid clearance of testosterone from the blood, leading to larger fluctuations between doses on TRT.

Impact on Treatment

SHBG level directly influences TRT dosing strategy. Men with high SHBG often need higher doses or more frequent injections to maintain adequate free testosterone. They may also benefit from protocols that include both testosterone and medications that modestly lower SHBG. Men with low SHBG may do better on lower, more frequent doses to avoid excessively high peaks that convert to estradiol.

Managing SHBG

SHBG is not directly treatable in the way testosterone is. But understanding your SHBG level helps optimize your protocol. High SHBG can sometimes be modestly lowered through boron supplementation at 6-10 mg daily, which has shown evidence of reducing SHBG by 10-20%. Addressing underlying causes like thyroid dysfunction or liver issues also helps. Ultimately, the most effective strategy is adjusting your TRT protocol to account for your SHBG level rather than trying to force SHBG into a specific range.