Learn More About Sex Hormone-Binding Globulin

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By Dr. Andrew I. J. Allshouse, N.D. – Revibe Men’s Health Seattle

Sex hormone-binding globulin (SHBG) is an important biomarker that is commonly used in the management of testosterone replacement therapy (TRT). SHBG is a protein produced by the liver that binds to sex hormones, including testosterone, in the bloodstream, which affects the bioavailability of these hormones in the body.

SHBG is most valuable in cases when it is high or even 2 to 3-fold higher than typical levels. For each increase in SHBG the serum total testosterone (TT) is exaggerated and bioavailable testosterone may remain the same or reduce. For cases such as these, the calculated free testosterone helps guide us in dose adjustments. Targeting the upper tertial of the normal limits of free testosterone may result in a high TT upon repeat testing. It is tempting to experiment with a lower dose to reduce the risks of the therapy and the free testosterone calculation can help guide in determining how much to reduce.

When a person undergoes TRT, their testosterone levels are increased, which can lead to a decrease in SHBG levels. This allows for a higher bioavailable testosterone level, improvements in symptoms, and less preservation of the testosterone present. More importantly, the total testosterone level becomes a more trustworthy tool for titrating one’s dose. Eventually, the total testosterone will decrease along with the SHBG and a dose that was once producing a higher level of testosterone will eventually result in a lower level. This can happen after 6 months or two years, so a blood test every 6 months will help us catch the change in chemistry, so we can match the dose appropriately if and when it happens.

If you are trying to figure out why you have symptoms of low testosterone and normal testosterone testing, then there is a chance a SHBG reading above 30 nmol/L is manipulating your total serum testosterone. A bioavialble testosterone calculator may be able to illustrate how your total testosterone would measure if your SHBG was closer to normal.