SHBG, or sex hormone-binding globulin, is a glycoprotein which binds to sex hormones such as testosterone & estradiol. Hormones bound to SHBG cannot enter a cell & activate the cell’s hormone receptor and thus are considered inactive. If you were to get a blood test & check for total hormones it would measure both free and SHBG bound hormones with an unknown proportion of this value being bound and thus inactive. Only free hormones are bioavailable (able to enter the cell & activate its receptor) and thus active. Therefore, SHBG inhibits the functions of hormones it’s bound to. SHBG is produced in the liver & released into the bloodstream. SHBG is also produced by the brain, uterus, placenta, & testis.
You can have either:
- High SHBG caused by:
Overactive thyroid (hyperthyroidism)
Alcoholic cirrhosis of the liver
Disorders of the androgen receptor (rare genetic problem)
Side effect of some drugs
If your SHGB is high then these factors listed above should be investigated and the problem rectified. Nettle supplementation can also help reduce high SHGB levels but should be used in conjunction with the appropriate treatment such as reducing excessive estrogen levels – which is often the cause.
- Low SHBG caused by
When Insulin levels are high
Side effects of drugs such as corticosteriods
Effect of overexposure to environmental chemicals with aromatase inhibitory activity
High insulin or IGF-1
Low SHBG levels are rarely a problem hormonally speaking as your hormones remain in the free and active state. It only becomes an issue when your hormone levels are elevated.