In an eggshell...
- SHBG is a carrier protein that binds to hormones such as oestrogen, testosterone and dihydrotestosterone
- The levels of SHBG affect the levels of sex hormones that are in a free state in the body
- Checking for your SHBG levels can indirectly provide insights on your sex hormone levels
Did you know our hormones have their own tiny vehicles to be transported to cells? 🚗
Hormones primarily exist in two states: a free state, where they can act on cells, and a bound state, where they’re bound to protein molecules and their action is restricted 🛑
One such protein carrier that’s on the hormone board is sex hormone-binding globulin.
As the name suggests, it’s on the radar as it binds to sex hormones, oestrogen, and testosterone.
When your sex hormone levels abnormally fluctuate, this little protein is also on the “need to question” list 📋
So, let’s dive in and learn more about it, and when you may need to test your SHBG levels.
What is Sex Hormone-Binding Globulin (SHBG)?
Sex hormone-binding globulin (SHBG) is an important reproductive hormone for both men and women. It is a glycoprotein primarily produced by the liver, which binds to sex hormones such as androgens and oestrogens.
While SHBG doesn’t directly act on cells, it acts as a carrier for these hormones instead (like Uber, but for hormones 🚗)
Once released to the bloodstream, SHBG binds to these hormones (dihydrotestosterone or DHT, testosterone and oestradiol), affecting their activity and availability to cells.
It’s like- once the hormones are bound to SHBG, they have to follow house rules 🚧
This protein also helps regulate how much of these hormones should be present in the body as well as its access to target tissues.
How does SHBG work?
The main function of SHBG is to act as a carrier for these sex hormones. The amount of sex hormones circulating in the blood is dependent on the levels of SHBG in the body.
But to understand its job description better, let’s nerd it out a bit.🤓
Hormones in our body generally exist in either a free state, or a protein-bound state. While free hormones are biologically active and can directly act on cells, bound hormones don’t have the same freedom.
Now, let’s talk about sex hormones. If SHBG levels are high, a larger fraction of the sex hormones will bind to it, leaving a smaller fraction free and biologically active.
AKA, if there’s too much or too little of androgens and estrogens, maybe it’s worth taking a look at SHBG levels too 👀
Normal Levels of SHBG in Women
Here are the typical ranges for Sex Hormone Binding Globulin (SHBG) levels in women. Keep in mind that SHBG levels can vary based on age.
What are the causes of low SHBG levels?
Low SHBG levels generally mean there’s fewer SHBG hormones but more free sex hormones in our body. The symptoms may be quite similar to elevated levels of testosterone and oestrogen.
Here are some related causes of low SHBG levels:
- Obesity and Inflammation: A pro-inflammatory cytokine called Tumor necrosis factor-alpha (TNF-α) has been identified as a key factor in reducing SHBG levels in obese individuals
- Liver Fat Content: Increased liver fat content might affect the liver’s ability to produce SHBG, leading to lesser production
- Genetic Mutations: Genetic mutations can lead to SHBG deficiency. For instance, genetic mutations can block SHBG secretion, leading to its accumulation within cells and failure to be secreted into the bloodstream
- Polycystic Ovary Syndrome (PCOS): Low SHBG levels are common in women with Polycystic ovarian syndrome. This in turn leads to higher levels of testosterone, with its symptoms showing up in the form of PCOS symptoms like hyperandrogenism and metabolic issues.
- Metabolic Disorders: Conditions like nonalcoholic fatty liver disease (NAFLD) and type 2 diabetes are linked to low SHBG levels.
What are the causes of high SHBG levels?
High SHBG levels generally mean there’s an overproduction of SHBG hormones and less of free sex hormones in our body. Here are some related causes:
- Age and Physical Inactivity: Older age and physical inactivity are associated with higher SHBG levels
- Liver Health: Liver disease or any abnormality in the liver cells can directly impact SHBG concentrations
- Genetic Factors: Genetic variations, such as polymorphisms or issues in the SHBG gene, can lower SHBG levels
- Hormonal Influences: Thyroid hormones, androgens, and estrogens regulate SHBG levels. Disorders affecting these hormones, such as hyperthyroidism and hyper- or hypoandrogenism, can in turn lead to altered SHBG levels
- Oral contraceptives: The use of birth control, specifically oral contraceptives (OCs), can lead to increased levels of sex hormone-binding globulin (SHBG) in females.
How Does SHBG Affect Fertility?
Since Sex hormone-binding globulin (SHBG) directly affects the availability of oestrogen and testosterone, a fluctuation in these levels affect our fertility as well. Here’s a breakdown:
1. SHBG and Polycystic Ovary Syndrome (PCOS)
If your SHBG levels are on the lower end, it may be associated with PCOS (Polycystic Ovarian Syndrome), or it could help calculate the risk of it.
Fluctuating sex hormone levels are one of the causes of PCOS. So, an SHBG test can be used as a biomarker to detect this and other symptoms of PCOS as well, such as hyperandrogenism, insulin resistance and abnormal glucose and lipid metabolism.
2. Risk of Infertility
Since SHBG levels directly affect the amount of sex hormones in our bloodstream, a disturbance in these levels could affect the reproductive system.
A recent study concluded that there is a non-linear association between SHBG levels and female infertility, AKA lower SHBG levels were linked to increased infertility risk.
3. Ovarian stimulation
Even during ovarian stimulation during IVF or egg-freezing cycles, the levels of SHBG influence the balance of circulating sex hormones.
Studies found that higher SHBG levels during the follicular and luteal phases are associated with better pregnancy outcomes.
4. Egg maturation
SHBG is also present in human follicular fluid, with its concentration varying between individual follicles.
This suggests that it may have a role in local regulation of steroid or sex hormone availability within follicles, needed for the egg’s maturation and growth. So SHBG levels could indirectly influence the egg’s maturity and quality.
How is SHBG Measured?
SHBG levels are typically measured through a simple blood test, and it doesn’t require any special preparations.
Most often, SHBG blood test reports are either recommended as a part of a full hormone test or compared along with the results of a total testosterone test.
This is because testosterone mainly circulates in the protein-bound form, especially bound to SHBG. Since this variation can affect the free testosterone in the body, these two tests may be recommended together.
SHBG Blood Test For Females in the UK via Amilis
If your SHBG levels fall outside the normal range, or if you’re going for a full hormone panel test, you’ll be able to get an estimate of your SHBG levels.
But here’s the thing: What if we told you that getting tested doesn’t have to revolve around long waiting times or GP referrals anymore?
Infact, when you opt for fertility testing via Amilis, here’s what you get:
- Zero waiting times, and the option to book a fertility test anytime, at your convenience
- A full hormone panel (which includes SHBG) at just £130 (50% cheaper than fertility clinics)
- A personalised report on your hormone levels and what your SHBG levels could mean for your fertility
- Book a free consultations with expert doctors, and with the best fertility clinics across the UK
When you opt for an SHBG test via Amilis, you also get a stellar support team (that’s us 👋) guiding you along at every step!
Figuring out where to get started? Book a free call, or take our personalised fertility quiz to know more!
We’re making healthcare accessible and affordable in the UK, one day at a time 💪🏻
