What is cholesterol?
Cholesterol is a waxy substance that is present in every cell in our bodies. It is made in the liver or you can get it by eating animal products. Cholesterol is very important for hormone and nerve cell production and making bile acid (used to digest food).1
There are 2 main types of cholesterol – often referred to as good and bad cholesterol.
High-density lipoprotein (HDL) is often referred to as ‘good’ cholesterol. This is because it helps to get rid of unwanted cholesterol in the bloodstream. Then there’s low-density lipoprotein (LDL), which is known for being ‘bad’ cholesterol because it causes blockages within the vascular system, resulting in circulatory issues.
A good way to remember the difference between the 2 types is LDL ‘litters’ the veins and arteries whereas HDL ‘happily’ clears the litter away, improving the circulation of the blood.
What causes high cholesterol?
High cholesterol (hypercholesterolemia) is often caused by poor diet. Eating too many foods that are rich in LDL (the bad cholesterol) leads to a build-up of this fatty substance in the blood, which can cause blockages in the veins and arteries and significantly increase your risk of heart disease, heart attack and stroke.
Fatty foods, high in LDL, not only lead to high cholesterol but to weight issues and other health concerns. Smoking and drinking too much can also lead to high cholesterol. It can also be a hereditary problem, running through families.2
Thyroid disorders can also be a cause of high cholesterol.1 Your body needs thyroid hormones not only to make good cholesterol but to get rid of the bad cholesterol. The connection between the thyroid and cholesterol is explained in more detail below.
What are the symptoms of high cholesterol?
High cholesterol doesn’t display any symptoms.2 Whilst often associated with obesity, you can be overweight without having high cholesterol. On the flip side, you can also be your ideal weight or underweight and have high cholesterol.
What is the connection between hypothyroidism and cholesterol?
If you have a thyroid disorder, and your thyroid gland is producing too many or too few thyroid hormones, this imbalance can lead to abnormal cholesterol levels in the blood.1
One of the essential roles of the thyroid gland is to produce hormones that support the liver process and remove excess ‘bad’ cholesterol from the body.
If you have an underactive thyroid (hypothyroidism) your thyroid isn’t producing enough hormones, particularly the T3 hormone (which stimulates the breakdown of cholesterol (lipolysis) and increases the number of LDL receptors) and so your body can’t break down and remove LDL cholesterol properly. This can lead to a build-up of LDL in the circulatory system.3
Research tells us that 13% of nearly 9000 people tested with high cholesterol also had thyroid disorders.4
It is often the case that an overactive thyroid (hyperthyroidism) can result in lower cholesterol levels. This doesn’t have associated health concerns and there isn’t any specific medical evidence to support this as yet.1
The only way to determine if you have high cholesterol is to have a blood test.2 This can be arranged by your GP or specialist. Using the same blood sample, technicians can identify thyroid and cholesterol issues. It is likely that you will be required to fast for 8 – 12 hours before your test.1
If you have high cholesterol with a normal TSH and FT4, it would be a good idea to ask your doctor to check your FT3 levels in case you are not converting to T3 very well which, in turn, could cause high cholesterol. Be aware that even slightly low thyroid hormone levels and/or slightly elevated TSH levels alone can cause cholesterol levels to be raised. 5
If you are unable to get FT3 testing done on the NHS, you can access it privately via our partner laboratories.
The usual treatment for high cholesterol is statins although there are non-statin options.6 Understanding the cause of high cholesterol is vital prior to determining the best course of treatment. If high cholesterol is caused by poor diet and lifestyle, then an adjustment to diet and exercise would, of course, be recommended. Cholesterol-lowering medications may also be prescribed.
If, however, the cause is connected to an underactive thyroid, then medication to treat hypothyroidism may, in turn, reduce cholesterol levels without the need for cholesterol-lowering drugs.1 Statins often cause muscular aches and pains, just like low thyroid so it could get confusing.
One study has, however, shown levothyroxine, a drug commonly used to treat hypothyroidism, to be ineffective when it comes to lowering cholesterol levels. The study showed that 17 out of 23 patients who were prescribed levothyroxine did not see a reduction in LDL levels.7 This may be due to the fact that the patients did not have their FT3 taken. Liothyronine (T3) treatment may have given a different picture.
Statins may also cause an increased risk of diabetes in certain people and as normal thyroid function is essential for regulating energy metabolism and blood glucose control, statins could potentially increase the risk of diabetes in a low thyroid patient. Statins also interfere with the production of mevalonic acid, which is a precursor in the synthesis of coenzyme Q10 (COQ10) which is an essential enzyme in the body for energy production and heart muscle health so taking some CoQ10 may be needed.8
Don’t let higher cholesterol scare you into taking statins without getting your doctor to check all your thyroid levels.
High cholesterol levels increase the risk of heart disease and stroke and must therefore be treated and monitored. Whilst an improvement in diet and lifestyle may help to reduce cholesterol levels, medication may also be required. Each case is unique and your doctor or specialist will provide information and guidance regarding the best treatment plan for you to reduce risks to your health.
For more support check out our online community:
Leonard J. How are thyroid and cholesterol related? Medical News Today. Published July 30, 2018.
NHS. What is high cholesterol? NHS. Published April 15, 2019.
Dullaart R. Triiodothyronine rapidly lowers plasma lipoprotein (a) in hypothyroid subjects. The Netherlands Journal of Medicine. Published online April 1995:179-184. doi:10.1016/0300-2977(94)00116-q
Willard DL, Leung AM, Pearce EN. Thyroid Function Testing in Patients With Newly Diagnosed Hyperlipidemia. JAMA Intern Med. Published online February 1, 2014:287. doi:10.1001/jamainternmed.2013.12188
Wang F, Tan Y, Wang C, et al. Thyroid-Stimulating Hormone Levels within the Reference Range Are Associated with Serum Lipid Profiles Independent of Thyroid Hormones. The Journal of Clinical Endocrinology & Metabolism. Published online August 2012:2724-2731. doi:10.1210/jc.2012-1133
Nissen SE, Stroes E, Dent-Acosta RE, et al. Efficacy and Tolerability of Evolocumab vs Ezetimibe in Patients With Muscle-Related Statin Intolerance. JAMA. Published online April 19, 2016:1580. doi:10.1001/jama.2016.3608
McAninch EA, Rajan KB, Miller CH, Bianco AC. Systemic Thyroid Hormone Status During Levothyroxine Therapy In Hypothyroidism: A Systematic Review and Meta-Analysis. The Journal of Clinical Endocrinology & Metabolism. Published online August 15, 2018. doi:10.1210/jc.2018-01361
Deichmann R, Lavie C, Andrews S. Coenzyme q10 and statin-induced mitochondrial dysfunction. Ochsner J. 2010;10(1):16-21.
Date updated: 08.04.21 (V1.3)
Review date: 09.03.22