High Cholesterol and Thyroid Disease

Medically Reviewed by Jennifer Robinson, MD on July 17, 2023
3 min read

If you have thyroid disease, you’re more prone to have high cholesterol levels. Though high cholesterol can be caused by an unhealthy diet and genetic factors, certain medical factors can play a role, too. In fact, as many as 13% of people who have hypothyroidism (underactive thyroid) will also have high levels of “bad” LDL cholesterol.

Hypothyroidism is also linked with too-high levels of triglycerides (blood fats that are associated with cholesterol). Both of those issues increase your risk for heart disease and stroke.

Hyperthyroidism (overactive thyroid) isn’t as common as hypothyroidism. It may cause low levels of “good” HDL cholesterol. If you’re diagnosed with hyperthyroidism, your doctor will monitor your cholesterol levels to make sure you stay healthy.

If you have thyroid disease, high cholesterol levels, or both, here’s what you should know.

Cholesterol is a waxy substance that circulates in your blood. Your body makes it, and it’s also found in animal foods. There are a couple different types of cholesterol:

  • High-density-lipoprotein (HDL) cholesterol, or “good” cholesterol. Low levels of HDL cholesterol can contribute to heart disease and other issues, especially if your LDL cholesterol and triglyceride levels are high.
  • Low-density-lipoprotein (LDL) cholesterol, or “bad” cholesterol. When your LDL cholesterol levels are too high, your arteries can become too narrow and get blocked. That can cause stroke and heart problems.
  • Triglycerides are fats from the food you eat that circulate in your body, which can be stored in fat cells. Triglycerides aren’t actually a type of cholesterol, but their levels are measured along with HDL and LDL in order to determine your odds of developing heart conditions.

Your thyroid is a butterfly-shaped gland in your neck. It produces hormones that help regulate your body’s metabolism. When you have hypothyroidism, your body doesn’t make enough thyroid hormones. This can increase your cholesterol levels. In fact, research suggests that even slightly low levels of thyroid hormones can cause a spike in cholesterol.

Thyroid hormones help your liver process blood. When your thyroid hormone levels are low, your liver processes blood more slowly, which can lead to higher levels of cholesterol in your bloodstream. That can cause a buildup of cholesterol in your arteries.

The good news is, treating thyroid disease may improve your cholesterol levels. Doctors treat hypothyroidism with thyroid replacement hormone medications. There’s no cure for hypothyroidism. That’s why improving your cholesterol levels doesn’t improve your thyroid hormone levels. Experts recommend that adults who’ve been diagnosed with high cholesterol levels get tested for an underactive thyroid.

If you’re being treated for an underactive thyroid, your doctor will monitor your cholesterol levels. Some people with hypothyroidism may not lower their cholesterol levels enough with thyroid replacement hormones. If that happens to you, your doctor may recommend you take other measures, such as eating healthier, exercising regularly, and taking a cholesterol-lowering medication.