Does Thyroid Affect Cholesterol?: Hypothyroidism, High Cholesterol And Thyroid Disease

Heart disease and stroke are associated with high cholesterol. High cholesterol can be caused by dietary habits and lifestyle choices, but it can also be caused by medical conditions, such as thyroid disorders.

An abnormal blood cholesterol level can be caused by excessive or insufficient thyroid hormone production.

The thyroid and cholesterol are discussed in this article. Additionally, the article discusses how to manage thyroid and cholesterol conditions.

Thyroid hormones are produced by the thyroid gland in the neck. It produces thyroxine (T4) and triiodothyronine (T3) as its main hormones.

The body uses these hormones throughout the body once they enter the bloodstream. T3 is thyroid hormone’s active form, and the body uses it in its natural form. T4 can also be converted into active T3 by body enzymes.

Among the functions of thyroid hormones are:

  • The development of the brain in children
  • Temperature of the body
  • The metabolic process
  • Development and growth
  • Heart function, brain function, muscle function, etc.

Thyroid-stimulating hormone (TSH) is produced by the pituitary gland to stimulate thyroid hormone production. Another hormone produced by the thyroid gland is calcitonin.

Key Takeaways

There does appear to be a connection between hypothyroidism (underactive thyroid) and high cholesterol levels. Here is a summary:

  • Hypothyroidism can directly cause increases in “bad” LDL cholesterol and triglycerides, as well as decreases in “good” HDL cholesterol[1][2][3][4][5].
  • This is because thyroid hormones play a key role in regulating cholesterol metabolism and removal from the body. With lower thyroid hormone levels, cholesterol cannot be processed and cleared as efficiently[1][4][5].
  • Even mild or subclinical hypothyroidism where thyroid levels are only slightly low can lead to adverse cholesterol changes[4].
  • Treating hypothyroidism with thyroid hormone replacement medication has been shown to decrease total and LDL cholesterol[3][5].
  • If left untreated, the high cholesterol levels caused by hypothyroidism significantly increase the risk of heart disease, stroke, and other cardiovascular issues[4][7][8].

In summary, there is a clear two-way relationship between hypothyroidism and high cholesterol. Hypothyroidism often leads to elevated cholesterol levels, which then compounds the health risks if not properly managed through thyroid treatment and cholesterol monitoring.


Background: Thyroid Disease

Having a low thyroid hormone level causes the thyroid to be underactive. Hypothyroidism is the result of this condition. In contrast, an overactive thyroid results from the production of too many hormones. The condition is known as hyperthyroidism.

An underactive thyroid affects almost 5% of Americans aged 12 or older.

A thyroid that is underactive exhibits the following symptoms:

  • depression
  • constipation
  • fatigue
  • dry skin and hair
  • heavy or irregular periods
  • fertility issues
  • low heart rate
  • The body is more sensitive to cold temperatures
  • reduced sweating
  • muscle and joint pain
  • weight gain

Background: Low Thyroid

A thyroid that is underactive can be caused by an autoimmune disorder like Hashimoto’s thyroiditis or surgically removed.

There is less of a chance of having an overactive thyroid. Overactive thyroids affect approximately 1.2% of Americans.

Symptoms of an overactive thyroid can include:

  • difficulty sleeping
  • bowel movements that are frequent or diarrhea
  • heat sensitivity is increased
  • fatigue
  • muscle weakness
  • mood changes
  • rapid heartbeat
  • shaky hands
  • nervousness or irritability
  • weight loss

Background: Overactive Thyroid

An overactive thyroid can be caused by a variety of conditions and circumstances. These include inflammation of the thyroid, Graves’ disease (the autoimmune condition), and excessive iodine use.

 Background: Cholesterol

Every cell in the body contains cholesterol, a waxy substance. In addition to making hormones and digesting fat, the body uses cholesterol to make bile acids.

In the arteries, too much cholesterol can cause a variety of problems, including heart disease.

During blood circulation, cholesterol attaches itself to proteins. Lipoproteins are bundles of cholesterol and protein.

High-density lipoproteins (HDL) and low-density lipoproteins (LDL) constitute the two principal lipoprotein bundles.

HDL is characterized by a high cholesterol-to-protein ratio. Known as “good” cholesterol because it eliminates cholesterol from the body, it also helps prevent heart disease.

Low-density lipoproteins have a low cholesterol-to-protein ratio. The term “bad cholesterol” refers to this type of cholesterol. Heart disease risk increases with higher LDL levels.

LDL cholesterol may be raised in the blood as a result of certain dietary choices. Some medical conditions, such as thyroid disorders, can also lead to high LDL cholesterol.

Cholesterol And Thyroid: Understanding The Connection

There is a close relationship between thyroid function and cholesterol levels. Adverse conditions can result from changes in this relationship.

It doesn’t take very low thyroid hormone levels to raise cholesterol. Subclinical hypothyroidism, a mild form of low thyroid levels, can cause high LDL cholesterol levels. It was found that even if thyroid hormone levels aren’t low, high TSH levels can raise cholesterol levels directly.

What is the connection between high cholesterol and an underactive thyroid?

In order for the liver to rid itself of excess cholesterol, thyroid hormones, most significantly T3, are essential.

Lack of thyroid hormones causes the liver to not be able to process cholesterol as efficiently. LDL cholesterol is removed from the blood less efficiently when the thyroid is underactive. As a result, total and LDL cholesterol levels may be high.

An underactive thyroid can be present in up to 13% of individuals with high blood cholesterol, according to studies.

The thyroid activity of an individual is inversely related to their cholesterol levels, according to further research conducted by the trusted source. Thyroid hormone supplements can therefore help a person manage their cholesterol levels.

Research has suggested that raised TSH levels in hypothyroidism can increase cholesterol levels in animals.

Do low cholesterol levels occur when the thyroid is overactive?

In the opposite case, an overactive thyroid can cause low blood cholesterol levels. An adverse health condition may result from low cholesterol.

A low cholesterol level, however, can lead to fewer complications than a high cholesterol level.

Tests for thyroid and cholesterol

If you suspect that your thyroid is underactive or overactive, you should see your doctor for further testing. Those with abnormal cholesterol levels should also consult a medical professional.

TSH and thyroid hormone levels will be measured in blood samples by the doctor. Thyroid function will be determined by the results, whether it is underactive, overactive, or functioning normally.

Food consumption can suppress thyroid hormone levels significantly, according to some researchTrusted Source, so it is recommended that a person fast before taking a thyroid hormone test.

Blood cholesterol levels may be tested by the laboratory technician or a doctor from the same blood sample. Separate cholesterol tests may also require fasting.

Treating thyroid problems and high cholesterol

In order to treat thyroid conditions and abnormal cholesterol levels, a doctor can suggest a treatment plan.

Underactive thyroid

A thyroid hormone replacement medication may improve cholesterol levels in people with underactive thyroids. Levothyroxine is commonly prescribed by doctors.

Doctors may prescribe statins if thyroid hormone levels are slightly below normal. Lowering cholesterol levels is the goal of these drugs.

The following are some statins that are commonly prescribed:

  • fluvastatin (Lescol)
  • rosuvastatin calcium (Crestor)
  • lovastatin (Mevacor, Altoprev)
  • pravastatin (Pravachol)
  • atorvastatin (Lipitor)
  • simvastatin (Zocor)

High cholesterol can also be treated with:

  • If applicable, losing weight
  • exercise on a regular basis
  • changing your diet to reduce saturated fat and increase fiber

Overactive thyroid

The production of thyroid hormone can be reduced with medication for people with an overactive thyroid.

Alternative treatments include thyroid surgery, which removes part of the gland or shrinks it with radioactive iodine.

As a result of thyroid hormone treatment, people with low cholesterol may see their cholesterol levels increase.


Thyroid disorders and abnormal cholesterol levels are clearly linked.

When a patient is diagnosed with high cholesterol for the first time, their thyroid hormone levels should be checked. As with those with an underactive thyroid, those with high cholesterol levels should undergo regular blood cholesterol testing to reduce their risk.

Depending on the severity of your thyroid disorder, you may see results once you treat it. For others with high cholesterol levels, lowering their cholesterol may require taking medication and making lifestyle changes.


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De Leo, S., et al. (2016). Hyperthyroidism. Link

Feingold, K. R., et al. (2020). The effect of endocrine disorders on lipids and lipoproteins. Link

Hyperthyroidism (overactive thyroid). (2016). Link

Hypothyroidism (underactive thyroid). (2021). Link

Nair, R., et al. (2014). Does fasting or postprandial state affect thyroid function testing? Link

Olssen, A. G., et al. (2017). Can LDL cholesterol be too low? Possible risks of extremely low levels. Link

Recalls, market withdrawals, & safety alerts. (2021). Link

Sinha, R. A., et al. (2018). Direct effects of thyroid hormones on hepatic lipid metabolism. Link

Willard, D. L., et al. (2014). Thyroid function testing in patients with newly diagnosed hyperlipidemia. Link

Zhang, X., et al. (2015). Thyroid-stimulating hormone decreases HMG-CoA reductase phosphorylation via AMP-activated protein kinase in the liver. Link

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