SHBG is short for Sex Hormone Binding Globulin.
This test is rarely ordered, which is unfortunate because it can give you a lot of information about the hormones in your body.
High levels can lead to symptoms of excess estrogen, excess thyroid, and low testosterone.
Low levels can lead to symptoms of low thyroid, low estrogen, and excess testosterone.
In this article, I will discuss how to interpret your SHBG test results, and list some common causes of elevated levels and low levels.
I will show how SHBG can be used to monitor your thyroid function if you are on thyroid medication.
I will also discuss some things that you can do to help you get your SHBG level back into the optimal range whether it is high or low…
SHBG is an acronym for sex hormone binding globulin.
It does what it sounds like it does – it binds up sex hormones.
Why is that important?
In order to understand this better we need to discuss how hormones work in general.
The vast majority of hormones in your body are bound to proteins in the bloodstream. This helps to stabilize the hormone so it can get to the targeted cells all over the body.
While it is bound, however, it is inactive and not available for the cells to use.
In order for the hormone to be active, it must break away from the protein. This makes it a “free” hormone and it can then enter the cells and turn on the cellular function it is designed to do.
This is called the Free Hormone Hypothesis.
The “free” hormones are therefore the “active” hormones.
The amount of “free” hormones is much smaller than the amount of “bound” hormones.
This protein binding is one of the ways that the body uses to regulate the hormone levels.
So what about SHBG?
SHBG levels naturally increase as we age. Since most hormone levels naturally decline as well, this makes a deficiency of those hormones (especially testosterone) even more pronounced.
Sex Hormone Binding Globulin binds to several different hormones. The body uses SHBG to inactivate these hormones in the bloodstream.
Too much of it can be bad because it can bind so much of the hormone that we can have symptoms caused by a lack of that hormone.
Too little can also be bad because it can cause an excess of certain hormones which also causes symptoms.
Even small changes in SHBG can cause substantial symptoms and problems.
SHBG has a stronger affinity for some hormones that others.
It will preferentially bind to sex hormones in this order (from highest affinity to lowest):
As you can see, SHBG has a greater affinity for androgens than estrogens.
You can therefore predict the symptoms you may have by knowing the effect that the SHBG level has on your androgen levels.
For example, if you have an elevated SHBG, it will bind DHT and testosterone which will cause symptoms of low testosterone (weight gain, depression, increased belly fat, loss of muscle, etc.).
With low levels of SHBG, you will have more unbound or free testosterone which will cause symptoms of high testosterone (acne, facial hair growth, PCOS, etc).
Hopefully you can see why it’s important to check your SHBG level if you are having any symptoms of hormonal imbalance to help you and your doctor determine what issues are going on in your body.
The optimal range for SHBG is 60-80 nmol/L. Any level below or above this range should be investigated.
There are several things that I will list below that can elevate SHBG levels.
An increase in either or both of these hormones will stimulate the liver to increase SHBG production.
A SHBG level > 80 nmol/L is considered too high.
Another hormone to keep in mind that is closely linked to SHBG is cortisol.
Cortisol is our stress hormone. In times of increased stress (physical or mental), our adrenal glands increase cortisol production.
An elevated cortisol level stimulates the liver to increase SHBG production.
Please realize that an elevated level of SHBG does not in itself cause any symptoms.
The symptoms are caused by the effect that the high SHBG level has on hormones in the body.
Most of the symptoms will be due to either excess estrogen and/or low testosterone:
If the elevated SHBG is caused by the situation of a high thyroid level (hyperthyroidism or excessive oral thyroid medication), you can also have symptoms related to the elevated thyroid such as tremor, palpitations and weight loss.
Treating an elevated SHBG has more to do with finding the cause of the elevation rather than treating the elevated SHBG itself.
There are several things you should consider doing:
The ratio of these 2 hormones is more important than the numbers themselves.
Check the levels in the middle of your cycle (2 weeks after your last period) for the best results.
If the ratio of estrogen:progesterone is >10:1, you have estrogen dominance that needs to be addressed.
If your estrogen level is normal, then it is highly likely that your thyroid is the culprit of your elevated SHBG.
Check a complete thyroid panel, especially free T3 and free T4.
If these are elevated and you are on thyroid medication, you may need to lower your dose or even change your thyroid medication.
If you aren’t on thyroid medication, you need to have more testing done ASAP to find the cause of your elevated thyroid (most likely Grave’s Disease).
I discuss several techniques to better manage your stress in my article on Adrenal Fatigue.
Low SHBG is more difficult to detect and often harder to treat.
As a result, it is often ignored much more than an elevated SHBG.
A low SHBG typically occurs in menopausal women or patients with hypothyroidism (low thyroid).
So if your SHBG is < 60 nmol/L, you should look at estrogen and thyroid as the probable causes if you are menopausal.
If you are still menstruating, then hypothyroidism is the likely cause.
If one or both of those hormones is low, SHBG levels will drop which will increase free testosterone, paving the way for conditions such as PCOS.
This series of hormone imbalances also appears to set up a person to develop insulin resistance.
In fact, a low SHBG level has been shown to be a strong predictor for type 2 diabetes in both men and women.
The symptoms associated with a low SHBG are typically caused by low thyroid hormone, low estrogen, and elevated testosterone. The include:
Keep in mind that your individual symptoms will depend on which hormones are out of balance and to what extent.
If you have a low SHBG, you should consider the following things:
Compare these tests with their optimal levels to determine if you have a thyroid issue.
If your thyroid function is low, it is probably affecting your SHBG level and you will need to consider taking a thyroid medication and doing other things to help boost your thyroid function.
After menopause, your estrogen levels will drop which can drop your SHBG level.
If that is the case in your situation, you might need to consider bioidentical hormone replacement therapy.
If your SHBG level is low, there will be less of it to bind to testosterone, so it may cause your free testosterone level to rise.
This can usually be alleviated by maximizing your thyroid medication which will raise your SHBG level.
One final benefit of checking your SHBG level is it a good indicator of the thyroid function in your body.
In states of low thyroid function, the SHBG level drops.
In states of high thyroid function, the SHBG level rises.
This allows the SHBG to be used as a marker to assess the thyroid hormone absorption and cellular function.
If you have low SHBG and hypothyroidism, you should test your SHBG level at the beginning of treatment to assess if you are on the right type of thyroid hormone and the right amount.
If you are taking a T4 only thyroid medication and your SHBG level does not increase, you may have a problem with peripheral conversion of T4 into active T3.
You therefore may need to change to a natural dessicated thyroid (NDT) or add T3 to your current regimen.
On the flip side, if after starting your thyroid medication your SHBG level rises > 80 nmol/L, that is an indication that your dose is too high and it should be reduced.
The sex hormone binding globulin level gives us important information on the status of several hormones in the body.
A high level is typically caused by estrogen excess and excess cortisol.
A low level is typically caused by low thyroid. It also is an indicator that you may be having issues with insulin resistance.
The key to treating an abnormal SHBG level is to identify what is causing the abnormality and correct it.
Doing this will help return the SHBG level to the optimal range and reduce symptoms.
Now it’s your turn…
Do you have an abnormal SHBG level?
Have you identified the cause or causes?
Please leave your comments below.
Most medical providers have been trained to only check the TSH when monitoring thyroid function.
But is the TSH enough to test your thyroid? Is it enough to monitor whether you are on the right dose or right type of thyroid medication?
The answer is a definite “no” and I will explain why in this article…
Let’s quickly review what the TSH is and what it indicates:
All thyroid activity actually begins in the hypothalamus of the brain. The hypothalamus secretes a hormone called Thyroid Releasing Hormone (TRH) which then stimulates the pituitary gland to secrete TSH.
TSH an acronym for Thyroid Stimulating Hormone. It’s purpose is to stimulate the thyroid gland to produce thyroid hormone.
The pituitary gland measures the level of T4 and T3 in the blood of the pituitary and secretes TSH in order to keep the levels of thyroid hormone in the optimal ranges.
When the body is healthy and working normally, this feedback loop works seamlessly to regulate thyroid function in the body.
As a reminder, if there are low levels of T4 and T3 in the pituitary gland, it will increase TSH secretion to try to stimulate the thyroid to produce more thyroid hormone, so the TSH level will rise. Conversely, if there is an excess of T4 or T3, the pituitary will decrease TSH production. The TSH level will drop or sometimes even go to zero.
The result is the TSH moves in the opposite direction of the thyroid hormone level. If you are low in thyroid hormone, your TSH will usually go high, and vice versa.
Remember, the TSH is an indicator of blood levels of T4 and T3 in the pituitary gland, which may not be the same as in the rest of the body. This is because the pituitary has a different deoidinase enzyme than the rest of the body.
Prior to the 1970s, the history and physical exam were the primary tools used to diagnose hypothyroidism, Grave’s Disease, Hashimoto’s Thyroiditis, and other thyroid conditions.
The TSH lab test was developed in 1975 and has been considered the gold standard for diagnosing and managing thyroid diseases ever since.
The vast majority of medical providers (doctors, PAs, NPs) are taught in their training to just use the TSH lab test to test for thyroid disorders and to monitor thyroid medications.
If you ask them to do a complete thyroid workup to see if you have thyroid disease, they will order a TSH and sometimes a T4 level or TPO antibody level. The other tests are rarely ordered, and even if they are, most providers don’t really know how to interpret them correctly.
Conventional medicine doctors are taught this simple rule – If the TSH is high, you have hypothyroidism. If it is low, you have Grave’s disease or you are on too much thyroid medication.
Sounds simple, doesn’t it? Unfortunately, evaluating the thyroid is much more complex than that.
I personally believe that in order to truly evaluate someone’s thyroid health, you need to order a complete thyroid panel. Those tests include:
If you want more information on each of these tests, what the levels are indicating, and optimal ranges for each, read my article here.
The sex hormone binding globulin (SHBG) can also be very helpful in assessing thyroid levels in the body, especially if you are on thyroid medication. Read more about it here.
So is checking the TSH enough to diagnose and manage thyroid disorders? No, because there are many situations in which the TSH will be falsely suppressed or at least lowered from what it really is.
Suppressing (lowering) the TSH level makes it look like the person has more thyroid hormone in their body than they really have. As a result, this may make it look like they are on too much thyroid medication when the opposite is actually true.
Also, if they haven’t been diagnosed with hypothyroidism, this may mask their true levels and prevent the diagnosis from being made because the TSH is “normal.”
Now let’s discuss some of the situations where the TSH may be falsely low:
The TSH can be transiently low or even undetectable in up to 20% of normal pregnant women with no other signs or symptoms of hyperthyroidism.
Several classes of drugs can suppress the TSH. The most common ones include:
It is common practice to give Hashimoto’s patients thyroid hormone medication as a treatment for their autoimmune disease.
This will obviously result in the TSH being suppressed a large percentage of the time in patients with Hashimoto’s. However, it brings the T4 and T3 levels into the optimal range.
Which is more important? Keeping the TSH “normal” or getting the T4 and T3 levels normal? I believe there is a strong argument that it is more important to optimize the T4 and T3.
The hypothalamic-pituitary-adrenal axis is a complex system that controls many of the hormone systems of our body. Research shows that when that system does not function correctly, it can have a major impact on the body. That is called HPA dysfunction.
HPA dysfunction is relatively common. When this system isn’t working properly, many of the hormone glands in our body – adrenal, thyroid, ovaries, and testicles – do not work normally. This results in reduced production of cortisol, thyroid hormone, and sex hormones.
People that have HPA dysfunction often have low TSH levels (because of reduced production of TRH), which makes it appear on lab tests that they have adequate or even high thyroid levels in the body. In reality, the majority of them have LOW thyroid levels, even though their TSH is in the low or normal range.
HPA dysfunction is commonly found in people with conditions such as Chronic Fatigue Syndrome and Fibromyalgia.
If you suffer from one of these conditions or know someone who does, you may realize that many of the symptoms appear the same as hypothyroidism:
This has led some experts to believe that hypothyroidism at the cellular level may be one of the primary causes of fibromyalgia and chronic fatigue syndrome.
In this study, researchers gave liothyronine (T3) to patients with fibromyalgia, even though their TSH was in the normal range. It resulted in the patients having a suppressed TSH consistent with what most doctors would call hyperthyroidism.
However, their fibromyalgia symptoms were greatly improved, and there were no significant side effects from taking the high doses of thyroid medication.
In a follow up study, the T3 medication was discontinued, resulting in the patient’s symptoms returning. When the medication was restarted, the symptoms improved again.
Could fibromyalgia and chronic fatigue syndrome be at least partly caused by undiagnosed hypothyroidism? It is something that should be considered.
This sounds way more complicated than it really is.
To put it simply, some people are born with a defect in the receptors in their cells where thyroid hormone attaches. Receptors are like locks on the cell wall. If the right key fits into those locks, it will trigger whatever function in the cell that the receptor was designed to do.
Below is a diagram of how this is supposed to work:
However, if the lock is defective in some way, it may not work right even when the right key fits into it.
This is what happens when there is a mutation in the thyroid receptor. The thyroid hormone may attach to it, but it may not trigger the function of that receptor like it was designed to do, at least not as efficiently as it would normally.
As a result, the cells will not be as responsive to thyroid hormone as they should be. This is called peripheral thyroid resistance.
Patients with peripheral thyroid resistance may have normal or even low levels of TSH, but their free T4 and free T3 levels will be low. The amount of thyroid hormone required to normalize their free T4 and free T3 will often result in a suppressed TSH.
Here is an example from a recent patient in my family practice office.
This 32 year old female with a history of Hashimoto’s thyroiditis came to my office complaining of persistent fatigue despite taking Armour Thyroid 120mg daily, selenium 200mcg daily, turmeric daily, and B12 supplements. She eats a whole food diet, exercises regularly, and gets good sleep.
Here complete thyroid panel is listed below:
As you can see, her TSH is in the normal range. If that was the only lab checked, you might think her thyroid level was normal. However, both her free T4 and free T3 are very low and her reverse T3 is <15 (which we want). Her TPO antibodies are slightly elevated.
This is typical of someone that has peripheral thyroid resistance. It will take more thyroid medication than usual to get adequate amounts of it into her cells, most likely because she has a mutation of her thyroid receptors.
I therefore increased her Armour Thyroid to 150mg in hopes of getting her free T4 and free T3 levels into the optimal range. That will most likely cause her TSH to be suppressed below the “normal range,” but it will be necessary to help relieve her fatigue and other hypothyroid symptoms.
Only checking a TSH level is not enough to monitor the thyroid activity and function in the body.
That is because the TSH is really only a measurement of thyroid hormone levels in the pituitary gland, which may be different than thyroid levels in the rest of the body.
Many things can cause the TSH level to be inaccurate, including some medications, autoimmune thyroid disease, chronic fatigue syndrome, fibromyalgia, thyroid receptor mutations, and even pregnancy.
In order to get a true assessment of thyroid activity in the body, it is important to get a complete thyroid panel and take a thorough history and physical exam.
Now it’s your turn…
Do you have symptoms of thyroid disease but have been told that your TSH is normal?
Have you had experience treating your thyroid issue even though your TSH is normal?
Leave your questions and comments below.