Testosterone is a steroid hormone produced in men’s testes throughout their life from puberty onwards. However, it starts to decline with aging, about 1-2% per year, from the age of 30 onwards. This process can be sped up through poor lifestyle habits, like too much alcohol, poor sleep, little exercise, too much stress and a poor diet.

Testosterone is responsible for regulating not just the sex drive (libido), but also bone mass, body fat and muscle mass as well as the production of red blood cells. When testosterone levels fall below normal levels this can result in reduced muscle mass, low libido, irritability, depression, poor concentration, loss of body hair, fatigue, and an increased risk of brittle bones.

It’s important to remember that libido is not just driven by hormones. If your lifestyle habits are out of balance, like doing too much or too little exercise, drinking too much alcohol or having psychological issues like depression or anxiety; they can all influence your libido too. So finding the root cause is important, rather than just thinking it’s a testosterone deficiency.

Why you should check Sex Hormone Binding Globulin (SHBG)

All hormones are carried around in the body by carrier proteins. Testosterone is carried through the body by SHBG predominantly and by albumin.[1] SHBG binds more to testosterone than to the estrogens.[2] The main role of SHBG is to control the availability of sex hormones to cells and to transport them through the body. In order to determine how much testosterone is getting into the cells, aka the ‘free testosterone’ we need to know your SHBG and your total testosterone levels and calculate the difference. Laboratories now do this calculation on your behalf to gauge the free testosterone. Measuring the free testosterone levels is a more accurate measure of testosterone status than the total testosterone.[3, 4]

The normal range for SHBG is 10-57mmol/L. An all too common situation as men get older is that is the SHBG begins to rise to high levels thereby block the availability of free testosterone to cells. The symptoms of high SHBG are similar to those of low testosterone as indicated previously.[5]

Therefore, we need to identify what causes high SHBG, in order to reduce it. For men it could be related to high thyroid levels (hyperthyroidism) or low growth hormone.[6,7] Other issues could be related to the liver, as SHBG is produced in the liver if one has diseases of the liver like NAFLD, hepatitis infections or cirrhosis, then SHBG can be high.[8,9]

Lifestyle factors can also play a role like drinking too much alcohol[10], smoking[11], and too much stress[12]. This stress can also come from over exertion as in too much training.

Long term implications of too much SHBG

There are potential long-term disease risks with too much SHBG. It is linked to bone loss and reduced bone density in a number of studies.[13,14] Also there’s an increased risk of Alzheimer’s disease and prostate cancer. [15,16]

What can be done to reduce it?

There are some dietary changes which can help. High protein diets are associated with reduced SHBG.[17] How much protein? As long as you’re getting your baseline 1.2 g/kg of bodyweight protein you should be fine, some people may need more based upon their training regimes. A liver function test can help determine your total protein levels as a first line blood check.

Getting the body fat levels down to healthy levels also helps to reduce SHBG.[18] For women that’s below 22% body fat and for men that’s below 20%.

Additionally, some supplemental minerals and vitamins can lower SHBG. Boron tops the list with researchers recommending an intake of up to 10mg / day lowering SHBG.[19] The best forms of boron are boron glycinate or citrate. Boron is especially powerful in lowering your SHBG and if your total testosterone is already high, you’re naturally going to have higher than normal SHBG, so it would be safer to start on a lower dosage of 3mg or 6mg/day of boron then follow up with a ‘free’ testosterone test 2-4 weeks later and see where your levels are at. Having your free testosterone levels between 2-4% is ideal.

Vitamin D3 lowers the SHBG and raises testosterone and optimal levels to aim for are around 50ng/dL. There is an additional synergy between boron and Vitamin D3 in that boron extends the half life of vitamin D3 in the blood, providing even more time for vitamin D3 to exert its long ranging effects. Fish oil also reduced SHBG[20] and the safest way to get your omegas is with eating the fish. Having 4 portions a week of either sardine, mackerel, wild salmon, herring or anchovy should be sufficient. The tinned versions have comparable if not more levels of omega-3’s.

So depending on your circumstances, you may need to look at your lifestyle, your diet and your training regime in helping you lower your SHBG and working with a functional medicine specialist will help you find your sweet spot to feel great!

Written by Miles Price