SHBG stands for Sex Hormone Binding Globulin. It also goes by other names such as SBP (Sex Steroid Binding Protein) and SSBG (Sex Steroid Binding Globulin). It is a protein naturally produced by the body. Its job is to bind to hormones in the body including Estrogen and Testosterone.
Why does our body need SHBG?
To understand this we must first look at something known as the “Free Hormone Hypothesis”. This hypothesis states that only hormones that are free (i.e. not bound or stuck on to proteins) are metabolically active in the body.
Let’s take Testosterone as an example. Let’s say our body has a total of 100 units of Testosterone and 60 units are bound to SHBG. This means effectively, our body only has 40 units of Testosterone to use. So why does our body do this?
There are several theories:
The Testosterone bound to SHBG serves as a buffer store.
For whatever reason if the amount of Free Testosterone falls, the body can easily and quickly release Testosterone bound to SHBG to use. As opposed to making more Testosterone which takes a much longer time.
SHBG protects Testosterone from being destroyed by the liver.
Our livers are our main metabolic organ in the body. It is constantly detoxifying us and getting rid of all sort of drugs and chemicals in our body that we do not need. The liver also breaks down hormones. SHBG protects Testosterone from being broken down so our body does not have to keep making huge quantities of Testosterone to replace it.
SHBG amplifies the actions of Estrogen.
Because SHBG binds more strongly to Testosterone than Estrogen, should there be a surge of Estrogen levels (for example during pregnancy), there is less Free Testosterone to counter the effects of Estrogen. This is much more pronounced in women.
So what is the problem if my SHBG level is high?
Remember the Free Hormone Hypothesis? If your SHBG level is too high, a large proportion of Testosterone will be bound to SHBG and therefore not available to your body to use. So although your Total Testosterone level may be nice, high and healthy, the actual Testosterone available to your body (i.e Free Testosterone) may be too low.
This explains why some men suffer from all the symptoms of Low Testosterone and yet seem to have a normal Total Testosterone level. This may even include embarrassing symptoms like Gynaecomastia or Male Breasts.
The symptoms that may prompt you to get your testosterone levels tested include:
- Easy fatigability, low energy
- Brain fog
- Weight gain or difficulty in losing weight
- Low libido (poor sex drive)
- Poor erections
- Mood swings or even depression
- Loss of muscle mass and strength
- Poor sleep
- Male Breasts (Gynaecomastia)
How do I know what my Free Testosterone level is?
You can do a blood test for Free Testosterone. However, the technique to measure Free Testosterone in the lab (called equilibrium dialysis) is a complex and expensive technique. So most commercial labs use a different but much less accurate method.
It is actually much easier (also more accurate and cheaper) to calculate the Free Testosterone level using 3 simple lab test results:
- Total Testosterone
- SHBG
- Albumin
There are many online calculators available for this. Just plug in the numbers and you get the Free Testosterone level. You will notice in these calculators, aside from Free Testosterone, it also tells you the Bio-Available Testosterone level.
What is the difference between Free Testosterone and Bio-Available Testosterone?
Again we return to the Free Hormone Hypothesis. Testosterone that is not bound to SHBG is metabolically active and called Free Testosterone. Testosterone bound to SHBG is not active.
However, there is another protein in the body and also binds Testosterone. This is called Albumin. The difference is Albumin only loosely binds Testosterone. So while the Testosterone is not Free, it can easily detach from Albumin and become active. Therefore it is “Bio-Available”.
So:
Free Testosterone = (Total Testosterone) – (SHBG-Testosterone) – (Albumin-Testosterone)
Bio-Available Testosterone = (Total Testosterone) – (SHBG-Testosterone)
OK. So why do I need to lower my SHBG levels?
A SHBG level that is too high may cause symptoms of low Testosterone even when the Total Testosterone levels are normal. It can also worsen symptoms when the Total Testosterone level is already low.
So if you have all the symptoms of Low Testosterone like tiredness, low libido, erectile dysfunction, gynaecomastia, loss of muscle strength etc and yet your Total Testosterone level are normal, it could be because your Free Testosterone is low.
Now if your Free Testosterone is low because your SHBG is too high, you may not want to receive yet more Testosterone to solve your medical issues.
You may instead want to try to lower your SHBG levels.
What causes high SHBG levels?
The first thing you need to do is to figure out if there is a medical problem that is causing your SHBG level to be abnormally high. This could be due to Medical Illnesses or Drug side effects. As a man ages, the SHBG level also increases. Of course there are always patients in whom we cannot find a cause and we term this “idiopathic”.
Medical illnesses and diseases that are known to increase the SHBG level include:
Testiscular Failure
When the testes are incapable of producing or producing too little Testosterone and other male hormones, the SHBG goes up. In such situations, the blood tests will show a high SHBG as well as a low Total Testosterone. Making the Free Testosterone even lower.
Diabetes
Men who suffer from Diabetes have a raised SHBG level. The cause is yet to be clarified but could be due to the low level of Insulin in the blood of diabetics. Interestingly, a very low SHBG level is a predictor for Diabetes. One theory is a low SHBG level indicates high circulating insulin. The high insulin is the body’s way of trying to overcome the peripheral tissues’ insulin resistance. Finally the pancreas fails, insulin levels drop and the patient becomes Diabetic.
Alcoholic Liver Disease
Interestingly this only happens in men. In women, SHBG levels are increased in liver diseases involving the bile ducts.
Hyperthyroid
Too much thyroid hormones increases SHBG levels. This can be due to an over-active thyroid gland or an overdose of thyroid hormone medications.
High Estrogen Levels
Estrogen levels can become too high in men for several reasons. This could be due to diet, medications, medical or genetic factors. A high level of Estrogen will cause SHBG levels to rise. And since SHBG binds more to Testosterone than Estrogen, this potentiates the Estrogen effect and can cause a lot of disturbing symptoms in men especially Male Breasts or Gynaecomastia.
Low Human Growth Hormone Levels
HGH levels may be suppressed in a variety of conditions. Some people are also born with a hereditary deficiency in HGH. SHBG levels have been observed to be raised in people who suffer from low HGH levels Conversely, medically replacing the HGH can cause SHBG to drop back to normal levels.
Smoking
Several studies involving a sizable study population (> 4000 participants) observed that smoking was related to increased SHBG levels.
HIV/AIDS
People living with HIV have been shown in studies to have higher SHBG levels. This could cause symptoms of low Testosterone along with the other symptoms of HIV infection.
Drug Side effects
Several drugs can increase SHBG levels. Hormonal drugs that mimic estrogen or thyroid hormone effects can increase SHBG levels. As well as certain Selective Estrogen Receptor Modulators (SERMs). Dexamethesone, a steroid used to treat a variety of medical conditions also increase SHBG levels. As well as Rifampicin, an anti-biotic used to treat Tuberculosis. This list is obviously not comprehensive and you should check with your Doctor if any medicine you are on can increase your SHBG levels.
Advancing Age
SHBG increases as men age. Men reach adult levels of SHBG at about 18 years old. By the time they are 80 years old, on average the SHBG would have doubled. Of course the SHBG rises faster in some individuals and can cause symptoms earlier on in life.
Idiopathic
Although we try, many times Doctors cannot identify an underlying cause for the raised SHBG. It may be transient or persistent. If it is persistent and symptomatic, we will discuss therapeutic options with patients.
Are there any natural ways to lower SHBG levels?
Several supplements have been studied that may play a role in lowering SHBG levels.
Zinc and Calcium
There are a couple of studies to show that both Zinc and Calcium bind to a portion of the SHBG and blocks the entrance to the steroid binding pocket. This suggests that Zinc and Calcium can help with increasing Free Testosterone levels. Although it does not reduce the level of SHBG per se. Unfortunately, in one report, this effect seems to work much better for Estrogen than Testosterone. So although molecularly it may make sense to take Zinc and Calcium supplements to raise Free Testosterone levels, the science is still far from conclusive.
Magnesium
There are studies to show that Magnesium bind to SHBG. Therefore taking up the space that would have bound Testosterone. Interestingly, there have been studies on the effects of magnesium supplementation on training. With athletes taking magnesium gaining more muscle mass compared to the control group. A small study in 2011 actually measured the Total and Free Testosterone in 3 groups of men. The first group did not train but took Magnesium. The second group trained but did not take Magnesium. The third group both trained and took Magnesium. After 4 weeks, the Total and Free Testosterone levels were higher in both the groups that took Magnesium compared to the group that did not. And was even higher in the group that took Magnesium and trained. Overall, there is still no large enough study to conclude that Magnesium does raise Free Testosterone levels. However a low doses, it is a safe supplement to take. At higher doses it can lead to abdominal discomfort and diarrhea.
Boron
Now this is the interesting one. Studies have found that Boron supplementation actually reduces the level of SHBG. Consequently increasing Free Testosterone levels as well as deceasing Estradiol levels. Even DHT and Vitamin D levels were raised. In a very small study (only 8 participants) after 1 week of Boron supplementation in Healthy Men, the Free Testosterone level rose an average of almost 30% while Estradiol levels dropped by 40%. Boron is safe to take in small daily doses. However excessive doses may cause side effects such as skin inflammation, abdominal pain, nausea and vomiting.
Tongkat Ali
Tongkat Ali is a popular herbal aphrodisiac in South East Asia. It also goes by its less well known scientific name – Eurycoma Longofolia. Studies have shown it reduces SHBG levels and increase Free Testosterone levels. Animal studies involving rats also show an increase in sexual behavior when fed with Tongkat Ali. Tongkat Ali is safe to take however many preperations are illegally laced with prescription medicines like Viagra. So as with all supplements, please ensure your source is reliable.
High Fat Diet
This is interesting. Studies have found that a high fat diet in men reduces the level of SHBG. (That said, there are also studies to show that fat and carbohydrate intake have no impact on SHBG levels). In fact, SHBG has been found to be low in men suffering from obesity. However, the Total Testosterone is also frequently low leading to consequently not much change in the Free Testosterone levels. However, excess adipose tissue also causes more aromatization (the conversion of Testosterone into Estradiol). So overall, the Estrogen effect can overcome the Free Testosterone effects leading to symptoms of Low Testosterone in men who suffer from obesity. This explains why in obese men, while most have excess fatty tissue in the chest, some actually develop male breasts from the excess Estrogen. Overall, using a high fat diet to reduce SHBG levels may not be the best idea.
High Protein Diet
A study published quite a while ago in 2000 using data from a huge data pool known as the Massachusetts Male Aging Study found that men on a high protein diet had lower SHBG levels. This is an associative study that does not prove causation. There was another study that showed when men suffering from obesity were placed on a high protein and high carbohydrate diet, the SHBG levels dropped and the Free Testosterone level increased. However they were also on an energy restricted diet and loss weight. So the weight loss may be a bigger factor than the high protein diet.
Are there any medical treatments to lower SHBG?
The first thing to do is always to try to identify an underlying medical cause and treat it.
While there does not exist a medicine that was solely created to reducing SHBG levels, Doctors have tried certain treatments that have worked.
Testosterone Replacement
Studies have found that giving the body an exogenous source of Testosterone will cause the body to down regulate its SHBG levels. This has been found to work on men who are actually deficient in Testosterone. They have also been used in men with normal Total Testosterone levels with similar effects. The thing is not all forms of Testosterone have the same effect. You should see a Doctor familiar with TRT before you decide to embark on this therapy.
Click here for our article on Testosterone Replacement Therapy
Human Growth Hormone Replacement
Human Growth Hormone (HGH) has been used very successfully as an anti-aging therapy. It is also abused by strongmen and athletes to help with repair and recovery from training. It was found that people who suffer from acromegaly (an abnormally high level of HGH in the body) have low SHBG levels. This led to studies on the use of HGH supplementation to reduce SHBG levels. This was confirmed when it was noted in studies that men who were deficient in HGH that received HGH therapy actually experienced a fall in SHBG levels and an increase in Testosterone levels.
In Summary
If you have symptoms of Low Testosterone or High Estrogen, it could be because your SHBG levels are too high.
Make sure when you go for a test, test for your Free Testosterone Level as well as your Total Testosterone level.
If your SHBG level is truly too high, talk to your Doctor about investigating for any possible underlying medical problems. Look through the medicines you are on to see if any one of them causes your SHBG to rise.
Talk to your Doctor about supplements or treatments you can take to reduce your SHBG levels.
Have a question? Feel free to put it in the comments section below.
Or visit us at our Men’s Health Clinic.
Have a question but need more privacy? Contact us on our Telegram channel. You can also follow us to get the latest news on STDs/HIV and Men’s Health.
Men’s Health – https://t.me/joinchat/uj8HDPzLtpk3NTA1
STD/ HIV Channel – https://t.me/joinchat/83vmPfDJa205ZTc1