Every cell in your body has receptors that bind with and respond to the hormones released by the thyroid gland. Thyroid hormones even play a role in your ability to metabolize lipids (fats), and any issues with part of your endocrine system may result in hyperlipidemia (high cholesterol). Below we will review thyroid function, explain the association between the thyroid gland and high cholesterol, discuss the cardiovascular risks associated with a thyroid condition, and go over different treatment options for thyroid issues and high cholesterol.
Review of the Thyroid System
Remember, the thyroid has a huge part in regulating our metabolism. The thyroid gland receives its instructions via a hormone (thyroid-stimulating hormone) secreted by the pituitary gland. This causes the thyroid to release several other hormones that will affect the rest of the body. There are three important hormones that we will review below.
- Thyroid-stimulating hormone (TSH): This is released by the pituitary gland to stimulate release of thyroid hormones. If there is not enough thyroid hormone being produced, TSH is usually high (hypothyroidism). If TSH is low, there is usually an excess of thyroid hormone (hyperthyroidism).
- Thyroxine (T4): This is primarily what is secreted by the thyroid gland. It is an inactive version of thyroid hormone, which is converted into active T3 hormone. Low T4 may indicate hypothyroidism while high amounts can suggest hyperthyroidism.
- Triiodothyronine (T3): This is active thyroid hormone, which is formed from the conversion of T4 to T3. T3 is the main player in metabolism regulation. Low T3 can indicate hypothyroidism and high amounts suggest hyperthyroidism.
What is cholesterol?
Cholesterol typically has a negative connotation, but it is critical for normal functioning of our bodies. It is formed in the liver and is a component of the cell membranes of all of our cells, resulting in appropriate transport of nutrients and materials from cell to cell as well as cell-to-cell recognition and communication. There are three major types of cholesterol (lipoproteins) in the bloodstream that we need to be concerned about.
- High-density (HDL) cholesterol: This is commonly know as the “good” cholesterol because the higher your HDL cholesterol, the lower your risk of heart disease or stroke.
- Low-density (LDL) cholesterol: This is the referred to as the “bad” cholesterol as high levels of LDLs tend to put you at increased risk for a cardiovascular event.
- Very low-density (VLDL) cholesterol: This is another type of “bad” cholesterol formed mainly by triglycerides (another type of fat); this lipoprotein helps cholesterol build up on artery walls.
Association between thyroid disease and cholesterol
Association between thyroid disease and cholesterol
The composition and transport of cholesterol is severely disrupted with thyroid dysfunction. As discussed above, cholesterol is mostly synthesized in the liver. In order to ensure proper functioning, this process is heavily regulated by thyroid hormones. Thyroid-stimulating hormone (TSH) increases the activity of an enzyme called HMG CoA reductase, which helps control the rate of cholesterol synthesis. Because you have increased TSH with hypothyroidism, the amount of cholesterol produced in the liver is increased. This is then taken out into the bloodstream via VLDL cholesterol.
VLDL travels in the bloodstream until it encounters an enzyme called lipoprotein lipase (LPL). T3 stimulates LPL to break down the VLDL, turning it into low-density lipoprotein (or LDL cholesterol), once the majority of triglycerides are removed. With hypothyroidism, there isn’t enough T3, which will increase the amount of VLDL in the bloodstream as there won’t be enough LPL enzymes available.
The VLDL-turned-LDL cholesterol circulates in the blood until it finds cells that have LDL receptors. Once it binds to the cell, the LDL is used for cell membrane maintenance or converted to other steroid hormones to be used elsewhere in the body. T3 increases the number of LDL receptors, which reduces the total amount of LDL cholesterol in the bloodstream. With hypothyroidism, the number of LDL receptors will be reduced, increasing the amount of LDL in the bloodstream.
Increased LDL in the blood will increase the risk that it will be absorbed into the inner lining of the blood vessels. Here the LDLs will oxidize, causing an inflammatory response and considered to be one of the major causes of arterial plaque formation. T3 may protect LDL from oxidation; however, high T4 can also increase LDL oxidation. In that sense, both hyper- and hypothyroidism can lead to the development of plaque formations, making is necessary to ensure our thyroid levels are under control.
Thyroid dysfunction and risk of cardiovascular disease
While cholesterol is an important component of heart health, thyroid hormones also have a direct impact on cardiovascular function. A team of scientists at Erasmus University in the Netherlands found that as T4 increases, the risk of developing heart disease is doubled, and there is an 87% greater risk of having a heart attack or stroke. Similarly, thyroid hormones also have an effect on blood pressure, insulin tolerance, and body mass index.
It is estimated that 1 to 11% of all patients with a cholesterol issue have some sort of subclinical hypothyroidism. If you have been diagnosed with both hypothyroidism as well as high cholesterol, it is important to first determine what is causing each of these problems. Before going on any sort of medication for a cholesterol issue, it is imperative your thyroid condition is addressed first. There is also some current debate on whether or not those with subclinical hypothyroidism and hyperlipidemia should even be treated.
Overall, the best approach here is going to be preventative. Make sure you’re getting in enough exercise. This will help increase your HDL levels, which will help counteract higher LDLs, which we would expect in someone with hypothyroidism, as well as protect your heart in the long run. If you have any form of hypothyroidism, stay active, follow a low inflammatory diet like the one outlined in The 30-Day Thyroid Reset Plan ,and take any measures necessary to reduce your stress to prevent any oxidation in your blood vessels. Just because you have hypothyroidism and hyperlipidemia doesn’t mean you can’t live a rich and full life!
Summary and What To Do
- Your thyroid dysfunction may be causing your high cholesterol.
- Thyroid dysfunction can also be linked to cardiovascular disease and can increase your risk for heart attack and stroke.
- Make sure you are active, maintaining a low inflammatory, thyroid supporting diet, and managing your stress via meditation etc. in order to keep your systemic inflammation under control.
- Make sure you are keeping track of your thyroid and cholesterol numbers when you change your diet, exercise, medications, etc. to ensure all your levels are where they should be.
- Work with a practitioner that can help you find the underlying causes to both of these issues and create a detailed plan for YOUR body! I work with many people that deal with this and know what to look for!
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