Sex Hormone Binding Globulin (SHBG)

What is Sex Hormone Binding Globulin?

Sex hormone binding globulin (SHBG) is a protein made in the liver. It binds tightly to specific sex hormones, oestradiol, testosterone, and dihydrotestosterone (DHT), transporting them in their inactive forms in the blood. That means they cannot be used by your cells, it’s one of the ways the body regulates its hormone levels.

SHBG levels can change because of:

• age

• sex

• chronic conditions

Testing SHBG levels can tell you how testosterone is working in your body. For example, high SHBG levels may mean there is less free testosterone available which can affect a man’s sex drive. While low levels mean more SHBG is available. In women, this can cause symptoms such as excess hair growth (hirsutism)^[1].

What are Normal SHBG Levels?

The reference range for SHBG varies depending on the testing laboratory.

The normal reference range for the NHS is as follows:

The healthy range for SHBG at our laboratory is:

Forth data below shows the average SHBG level according to sex and age. For both sexes across all ages, SHBG levels are within the healthy range. However, SHBG levels typically rise in men as they get older because of declining testosterone which can be seen in the graph below.

Causes and Symptoms of Low Sex Hormone Binding Globulin Levels

If SHBG levels are low, it means there could be more sex hormones available for your body to use freely. The causes and symptoms of low SHBG can vary between men and women.

Causes

Low SHBG levels indicate a greater amount of free testosterone circulating in the blood. In women, high testosterone levels may be associated with polycystic ovary syndrome (PCOS).

PCOS is a common hormonal imbalance in women that can cause irregular periods and acne, and affect your chances of getting pregnant. It is associated with obesity and increases the risk of developing type 2 diabetes and heart disease^[3].

Decreased SHBG levels in men and women are also linked to:

• An underactive thyroid (hypothyroidism)

• Obesity

• High blood insulin (hyperinsulinemia)

• Excess growth hormones

• Family history of low SHBG^[4]

Some research suggests that low SHBG levels may be related to some factors associated with the development of metabolic syndrome, like altered blood fat profiles, particularly in men^[5].

Symptoms

In women, low SHBG levels are commonly associated with PCOS which can cause:

• Acne

• Weight gain

• Hirsutism or excess facial and body hair

• Mood swings

• Hair loss on the head

• Increased risk of cholesterol and type 2 diabetes

• Difficulty conceiving

• Irregular or absent periods^[6]

PCOS affects 20% of women and causes psychological symptoms, like:

• Reduced quality of life

• Anxiety

• Depression

• Low self-esteem

In men, symptoms of low SHBG include:

• Acne

• Mood swings

• Fluid retention

• Liver disease

• Weight gain

• Increased muscle mass

• Increased risk of blood clots

• High blood pressure^[7]

Metabolic syndrome is a group of health issues that increase the risk of developing type 2 diabetes and heart and circulatory conditions. Metabolic syndrome may not cause any symptoms but you could be at a greater risk if you:

• are obese

• are sedentary

• smoke

• eat an unhealthy diet

• drink lots of alcohol

• are Hispanic or South Asian^[8]

Increasing Your SHBG Levels

Treatment for low SHBG levels will depend on the underlying cause. If you require medical treatment, your doctor will explain your results and the type of treatment you might need.

However, there are some things you can do to help raise your SHBG levels naturally.

Exercise and weight loss

Because low SHBG is predictive of metabolic syndrome, and is low in obese people, the effect of exercise on circulating SHBG has been researched.

A study involving 36 overweight, sedentary young men found that a 12-week resistance training program increased SHBG levels^[9]. Another study involving obese postmenopausal women found that 16 weeks of aerobic exercise raised SHBG levels and could prevent obesity-induced metabolic syndrome^[10].

High-fibre diet

The types of food you eat may be influencing your SHBG levels, particularly if you are overweight or obese. Research shows that a high sugar intake and consuming foods with a high glycaemic index (GI) were associated with lower levels of SHBG. Women who ate more dietary fibre, on the other hand, were more likely to have increased SHBG levels.

Examples of fibre-rich foods include:

• Oats

• Legumes (lentils, beans)

• Fruit (apples, oranges, pears, cherries, berries)

• Vegetables (sweet potato, spinach, peas, Brussels sprouts, broccoli)

• Wholemeal or granary bread, wholewheat pasta, brown rice

• Nuts (almonds, Brazil, cashews, pistachios)

Causes and Symptoms of High Sex Hormone Binding Globulin Levels

High SHBG levels usually indicate a lower concentration of free sex hormones in circulation. There are a range of causes and symptoms linked to low SHBG levels.

Causes

If your SHBG levels are high it means your liver is overproducing the hormone. It can be a sign that your body is trying to correct imbalanced hormone levels or that your liver cells are not functioning as they should be.

Some of the common causes of high SHBG in men and women are:

• Anorexia

• Pregnancy (in women)

• An overactive thyroid (hyperthyroidism)

• Low testosterone levels

• Low growth hormone levels

• Liver disease

When SHBG levels are high, a higher proportion of sex hormones are bound and inactive. A short-term increase in SHBG levels can have protective benefits for the heart. However, high SHBG levels in the elderly aren’t desirable because they have been linked to an increased risk of fractures and weak bones^[11].

Symptoms

In men, common symptoms of high SHBG levels are:

• Erectile dysfunction

• Low sex drive

However, symptoms can vary depending on the underlying cause of high SHBG levels. For example, common symptoms of hyperthyroidism are:

• Mood swings

• Weight gain

• Anxiety

• Irritability

• Tiredness

• Muscle weakness

• Heat sensitivity

• Sleep trouble

• Thirst

• Itchiness

• Diarrhoea^[12]

Lowering Your SHBG Levels

If an underlying medical condition is causing high SHBG levels, treating this may help to reduce them. There are certain lifestyle changes you can make to help reduce SHBG, including:

• Diet changes

  Eating a diet that is high in protein may help to lower SHBG levels, particularly in men. Protein-rich food include meat, fish, tofu, edamame, eggs, legumes, nuts and seeds.

What is an SHBG Blood Test?

Sex hormone binding globulin levels are measured as part of a wider hormone test, measuring the concentration of female and male sex hormones. It is usually carried out if you have any symptoms which may suggest high or low levels of testosterone.

Why Test Your SHBG Hormone Levels?

You should test your SHBG levels if you are experiencing any of the symptoms listed above. The test will tell you how testosterone is working in your body.

In men, an SHBG test may cause symptoms associated with having too little testosterone, while women may be experiencing symptoms associated with too much. These can help to establish why you may be experiencing specific symptoms, and enable you to make certain lifestyle changes or receive medical treatment.

How Does it Work?

You can test your SHBG levels at home with one of the following Forth tests:

• Female Hormone Imbalance Blood Test
• Male Hormones Blood Test
• PCOS Blood Test
• Advanced Health Test
• Ultimate Health Test

To get your results, simply:

• Choose your test based on your requirements

• Your kit will be sent to your address

• Collect your sample by following the instructions enclosed in the kit

• Post your sample back to the lab for analysis using the prepaid envelope

• One of our GPs will review your results. You can access their comments on your secure health dashboard

Written by Leanne Edermaniger

Based in the UK, Leanne specialises in writing about health, medicine, nutrition, and fitness.

She has over 5 years of experience in writing about health and lifestyle and has a BSc (hons) Biomedical Science and an MSc Science, Communication and Society.