Thyroid hormones have a direct effect on cholesterol levels - too much or too little thyroid hormone can contribute to changes in cholesterol which can be a risk factor for type 2 diabetes, obesity and more.

What is the Thyroid Gland?

The thyroid gland is a butterfly-shaped organ located at the front of the neck. It produces hormones that affect nearly every organ and system in the body. Often called the body's "thermostat," its main function is to regulate metabolism and body temperature, but it also plays crucial roles in body weight, energy levels, menstrual cycles, and cholesterol levels.

The thyroid produces hormones by absorbing iodine and converting it into T3 (Triiodothyronine) and T4 (Thyroxine) with the help of the enzyme thyroid peroxidase. The balance of these hormones is controlled by the pituitary gland, which produces TSH (Thyroid Stimulating Hormone), a hormone that signals the thyroid to produce T4 (inactive hormone) and small amounts of T3 (active hormone).

Since T4 is considered inactive, it must travel to the liver to be converted into T3 to become biologically active and usable by the body. Anything that disrupts the secretion of TSH, prevents the conversion of T4 to T3, or affects the body’s ability to utilise thyroid hormones can lead to thyroid imbalance and the development of thyroid-related conditions.

Common Signs of an Underactive Thyroid (Hypothyroidism)

When the thyroid is underactive, it leads to low production of thyroid hormones, causing the body's metabolic processes to slow down. Symptoms include:

Cold hands and feet
Weight gain and difficulty losing weight
Fatigue
Depression
Constipation
Heavy periods
Elevated cholesterol (particularly LDL)

Hypothyroidism can result from autoimmune conditions like Hashimoto's Thyroiditis, or from surgical removal of the thyroid gland.

Common Signs of an Overactive Thyroid (Hyperthyroidism)

In hyperthyroidism, the thyroid produces too much thyroid hormone, speeding up metabolism. Symptoms include:

Insomnia
Weight loss
Anxiety
Diarrhoea or frequent bowel movements
Irregular or absent periods
Subfertility
Low cholesterol levels

Hyperthyroidism can be caused by Graves' Disease, an autoimmune disorder, inflammation, or excessive iodine intake.

How Thyroid Health Affects Cholesterol

Cholesterol is a lipid that plays an essential role in hormone production, the synthesis of bile acids to digest dietary fats, and in maintaining cell membrane structure. Thyroid hormones have a critical role in regulating lipid metabolism, including cholesterol levels in the body. Here are 3 ways the thyroid and cholesterol are interconnected:

1. Thyroid Function and Cholesterol Metabolism

Hypothyroidism (Underactive Thyroid): When the thyroid is underactive, it produces insufficient thyroid hormones (T3 and T4). These hormones are essential for maintaining cholesterol balance. Without enough thyroid hormone, the liver's ability to process and remove cholesterol from the bloodstream is impaired, leading to:

Elevated total cholesterol
High LDL cholesterol (often referred to as "bad" cholesterol)
Increased triglycerides

Hyperthyroidism (Overactive Thyroid): In hyperthyroidism, the thyroid produces excess thyroid hormones. This leads to increased metabolism, which in turn lowers cholesterol levels, particularly:

Reduced LDL cholesterol
Lower total cholesterol

2. Thyroid Hormones and Lipid Clearance

Thyroid hormones regulate the activity of specific enzymes and proteins involved in lipid metabolism, including liver enzymes responsible for clearing cholesterol from the bloodstream. For example:

Thyroid hormones increase the number of LDL receptors on liver cells, promoting the uptake of LDL cholesterol from the blood.
In hypothyroidism, this process is impaired, leading to higher circulating cholesterol levels.

Cholesterol clearance is slower, resulting in higher cholesterol levels in the blood in those with hypothyroidism.

3. Impact of Cholesterol on Thyroid Health

While thyroid hormones directly influence cholesterol metabolism, the reverse is also thought to be true to some extent. Elevated cholesterol levels can sometimes negatively impact thyroid health. Some of which include:

High cholesterol levels have been associated with an increased risk of thyroid dysfunction, particularly autoimmune thyroid diseases like Hashimoto's thyroiditis.
Dyslipidemia (abnormal cholesterol levels), especially high cholesterol, has been linked to a greater risk of developing thyroid disorders, though the exact mechanisms are still unclear.

Thyroid health and cholesterol levels are intricately connected. Thyroid hormones help regulate cholesterol metabolism, and any disruption in thyroid function, whether underactive (hypothyroidism) or overactive (hyperthyroidism) can have a significant effect on cholesterol levels. Proper thyroid care is essential to prevent and manage cholesterol imbalances and related health risks. If you have symptoms of thyroid dysfunction or abnormal cholesterol levels, it's important to speak to a Body Fabulous Practitioner.

Testing for thyroid health & cholesterol

Thyroid Balance Report - A DNA moth swab test to assess genes that can increase your risk to thyroid disease, inflammation and autoimmunity

Thyroid Function with Antibodies - A blood test to assess thyroid hormone levels including thyroid antibodies for an in-depth picture of your thyroid health.

The Ultimate Methylation Vitamin Test - A blood test to assess nutrient status including iron (ferritin) and vitamin D. As well as markers for cholesterol levels and triglycerides.

Annie Davies
Clinical Nutritionist
Body Fabulous
www.mybodyfabulous.co.uk