- How Insulin May Affect SHBG.
- How SHBG Affects Free versus Bound Sex Hormones.
- Impact of Low SHBG.
- Impact of High SHBG.
- How to Increase SHBG (When it’s Too Low).
- How to Reduce SHBG (When it’s Too High).
- Causes for High SHBG (in Men).
- Sex hormone binding globulin (SHBG).
- SHBG is a glycoprotein primarily produced in the liver.
- Most commonly found in the bloodstream.
- It binds the sex hormones, including testosterone and estrogen.
- Transports these hormones throughout the body.
- Link between insulin / glucose and IGF-1:
- Glucose drives insulin.
- Insulin drives SHBG.
- SHBG drives free testosterone.
- Free testosterone drives IGF-1.
How Insulin May Affect SHBG
- Inverse relationship between serum insulin and SHBG
- Ie, if insulin is low, SHBG is high.
- Likely that insulin inhibits production of SHBG.
- In other words, low insulin may negatively influence level of free testosterone.
How SHBG Affects Free versus Bound Sex Hormones
- Testosterone and sex hormones are referred to as “bound” when attached to SHBG.
- When these hormones are not bound to SHBG, they are referred to as “free”, or “bioavailable”.
- Most sex hormones circulating are bound to SHBG.
- Only 1-2% are free and biologically active.
- Relative binding affinity:
- DHT > testosterone > androstenediol > estradiol > estrone
Impact of Low SHBG
- High levels of (free) sex hormones.
- Excess growth of cells leading to the formation of certain cancers.
- Elevated triglycerides and LDL.
- Linked with cardiovascular illnesses, type 2 diabetes, and high blood pressure.
Impact of High SHBG
- Decreases the amount of free testosterone.
- Associated with infertility, a decreased sex drive, and erectile dysfunction.
- Reduced muscle growth and impaired post-workout recover.
- Reduce bone mass.
How to Increase SHBG (When it’s Too Low)
- Reduce calories.
- Aerobic exercise.
How to Reduce SHBG (When it’s Too High)
- Conversely, exercise and reduced calories may produce unwanted increase SHBG.
- Therefore, avoid over-training.
Causes for High SHBG (in Men)
- Elevated estradiol levels from conversion of testosterone.
- Extreme weight loss in anorexia nervosa.
- Certain medications.
- Liver cirrhosis.
- Cigarette smoking.
- Compromised liver detoxification (alcohol abuse, meds, heavy metals etc.)
- Testicular cancer.
Inverse association between serum insulin and sex hormone-binding globulin in a population survey in Sweden, Bledar Daka, Thord Rosen, Per Anders Jansson, Lennart Råstam,Charlotte A Larsson, and Ulf Lindblad, Endocrine Connections, 2013 Mar 1; 2(1): 18–22, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3680959/
- Neel Duggal, July 23, 2015, http://blog.insidetracker.com/testosterone-action-versus-testosterone-levels-why-shbg-matters