It’s no secret that testosterone plays a central role in men’s health. Optimum levels of this sex hormone can contribute to a healthier cardiovascular system, increased muscle mass, stronger bones, and mood improvements.
With testosterone, however, it’s not merely a case of “more is better.” Hormone regulation is a necessary part of managing your health. And when it comes to sex hormones – just like so many things in life – moderation is key.
Moderation is where SHBG, or Sex Hormone Binding Globulin, comes in. It is your body’s tool to regulate the bioavailability of your sex hormones.
Too much testosterone, in men or women, can lead to a host of unpleasant symptoms, among them fluid retention, acne, mood swings, and increases in appetite. Insufficient levels, on the other hand, can lead to reduced muscle and bone mass, sexual dysfunction, and even infertility.
What is SHBG?
Testosterone in the body comes in two forms: It can be bioavailable, meaning it is free to exert effects on your body, or it can be “bound” to SHBG, or Sex Hormone Binding Globulin.
SHBG is a glycoprotein produced in the liver. It circulates in your bloodstream and binds to sex hormones to transport them. This binding regulates the bioavailability of your sex hormones and prevents excessive levels from wreaking havoc on your system.
SHBG can bind to any of the 17 sex hormones, including testosterone, dihydrotestosterone (DHT), and estradiol, which is a form of estrogen. Although not a hormone itself, SHBG is an integral part of your endocrine system.
Once bound to SHBG, the sex hormone is no longer available for the cells to use. The bound hormone is still part of your “total level” of the particular hormone, though.
In this regard, SHBG does not increase or decrease your total levels of a hormone – rather, it increases or decreases its bioavailability.
Normal levels of SHBG contribute to an optimized hormonal profile, which can improve your general health, lower your risk of certain diseases, and bring improvements in athletic performance and cognitive function. What constitutes a healthy level of SHBG will vary significantly on several factors, including your age and gender.
Normal SHBG levels in males are between 10 and 57 nanomoles per liter (nmol/L), and females between 18 and 144 nmol/L. (1) You might not be too concerned about the exact figures, but it can be useful to know the signs and symptoms associated with abnormally high or low levels of SHBG.
How Does SHBG Affect Testosterone Levels?
Hormones exert effects on your physical and mental health, and this is particularly true for sex hormones. Sub-optimal levels of free testosterone can negatively affect the health of men and women alike.
Again, SHBG does not increase or decrease your total testosterone levels. It can only increase or reduce the amount of free, or bioavailable, testosterone in your body. In general, low SHBG levels mean you have less bound testosterone in your system and higher bioavailability.
The increase in free testosterone can be beneficial … to a point. It can help improve your cardiovascular health, increase your muscle and bone health, and stabilize your moods.
But if SHBG levels are too low, the excess free testosterone can potentially have adverse effects for both men and women. (2)
Symptoms of excessive free testosterone include:
- Weight gain
- Mood swings
- Fluid retention
Low levels of SHBG also are associated with increased levels of triglycerides and low-density lipoproteins. As a result, they can be linked to heart disease, type 2 diabetes, and high blood pressure. (3),(4),(5)
In contrast, consistently high SHBG levels will mean you have more bound testosterone and less free testosterone. The reduced bioavailability can result in symptoms associated with low testosterone, including:
- Reduced muscle mass and bone density
- Reduced libido, erectile dysfunction, and sexual dysfunction
- Mood changes and depression
- Sleep disturbances
High SHBG can have a negative effect on your athletic performance, with reduced bioavailability of testosterone hampering your post-workout recovery. Even more seriously, research indicates that high levels of sex hormones can lead to excess growth of cells, possibly increasing risk factors for certain diseases.
SHBG does not just affect the bioavailability of testosterone in your body. It also binds to all of your sex hormones, including estrogen. Research now suggests that this can lead to reduced bone density in men and women and, as such, an increased risk of osteoporosis.
Does SHBG Increase with Age?
SHBG levels fluctuate throughout your life. Before puberty, SHBG levels are higher than they are in adulthood.
Following the onset of puberty, levels decrease and stabilize over the years, with men generally having a lower SHBG level than women. As a man moves into older age, a decline in total testosterone is associated with an increase in SHBG.
How Can Men Reduce SHBG?
Maintaining optimum levels of SHBG is crucial for your health, athletic performance, and post-workout recovery. This is particularly relevant for aging men.
As total testosterone levels drop, it’s vital to optimize its bioavailability. A blood test can confirm whether your SHBG levels are high.
If they are, simple lifestyle changes can help you lower it.
Increase the amount of plant-based carbohydrates in your diet, focusing on cruciferous vegetables, like broccoli and cauliflower. These veggies can help metabolize estrogen, which will lower your SHBG.
Studies have shown, however, that omitting all animal-based proteins and switching to a vegetarian diet may actually increase your SHBG levels. Adjust your diet to include less fat and more protein.
Excess fat in your diet can lower your total testosterone levels, whereas excess protein does not have the same impact. Avoid over-consumption of alcohol, caffeine, and sugar.
Low levels of zinc, magnesium, and vitamin D are associated with lower testosterone levels. The best way to boost these is by introducing foods like spinach, quinoa, nuts, dark chocolate, black beans, and the like.
Supplementing with 5-10mg per day of boron also can have a positive effect on your testosterone levels. Diindolylmethane (DIM) supplementation can improve your body’s estrogen metabolism, which further lowers SHBG.
If you’re still struggling with low levels of bioavailable androgens, however, you might want to consider taking supplements that help free up bound testosterone (like these). Commonly referred to as testosterone boosters, these supplements can make a dramatic difference in the amount of free testosterone available in the body.
Weight training can increase your total testosterone levels. Studies have shown, however, that over-training can actually result in higher levels of SHBG and reduce testosterone bioavailability.
These higher levels can interfere with your post-workout recovery and reduce your overall athletic performance. If you are trying to lower your SHBG, you need to monitor your levels during a training program to prevent over-training.
Monitoring your SHBG levels is a useful tool for getting a picture of your overall health. Moderation is key, and optimum levels will enhance your hormonal profile.
Minor lifestyle adjustments in diet and exercise can help regulate your SHBG levels and help you avoid symptoms associated with excessively high or low free testosterone. Before making any adjustments to your diet or exercise regime, consult with a medical professional to confirm your SHBG levels through a blood test and get advice tailored to your body.