Your Thyroid and High Cholesterol: The Connection

by Mary Shomon Patient Advocate

According to the U.S. Centers for Disease Control and Prevention, almost 37 percent of the U.S. population has high cholesterol levels that put them at high risk for heart disease and stroke. What you are less likely to hear, however, is that a substantial subset of people with elevated cholesterol are hypothyroid, and proper diagnosis and optimal treatment for the underactive thyroid could resolve their cholesterol problems. Let’s explore the important relationship between your thyroid and high cholesterol.

What is cholesterol?

Cholesterol is a waxy, fat-like substance that is primarily found in the food you eat, including animal foods like meats and full-fat dairy products. Your liver also makes some cholesterol.

When you have your cholesterol checked, your doctor will typically give you four key numbers:

Low-density lipoprotein (LDL) cholesterol is the "bad" cholesterol that increases your risk of developing heart disease. As it travels through your bloodstream, LDL can leave behind hard deposits on the walls of your arteries. Over time, these deposits narrow and stiffen your arteries and can cause a condition known as atherosclerosis, or “hardening of the arteries.” These narrowed arteries can then get clogged by clots, blocking blood flow to your brain or your heart and potentially causing a heart attack or stroke.

High-density lipoprotein (HDL) cholesterol is the "good" cholesterol that reduces your risk and protects you against heart disease. HDL also helps remove cholesterol from your body.

Triglycerides are a type of fat in your blood that can increase your risk of developing heart disease.

Total cholesterol is the sum of HDL, LDL, and triglycerides, divided by five.

What is high cholesterol?

Elevated cholesterol — known as hyperlipidemia or hypercholesterolemia — is typically due to three factors:

  • You overconsume foods high in saturated fats

  • You have a genetic propensity to produce too much cholesterol

  • You are hypothyroid

According to the American Diabetes Association, these are the latest optimal target cholesterol levels for men and women:


  • LDL Less than 100 mg/dL

  • HDL Greater than 45 mg/dL

  • Triglycerides Less than 150 mg/dL

  • Total Cholesterol Less than 200 mg/dL


  • LDL Less than 100 mg/dL

  • HDL Greater than 55 mg/dL

  • Triglycerides Less than 150 mg/dL

  • Total Cholesterol Less than 200 mg/dL

High cholesterol is diagnosed when you have elevated LDL, low HDL, elevated triglycerides, and/or elevated total cholesterol.

Cholesterol and your thyroid

Hypothyroidism can cause levels of total cholesterol, LDL bad cholesterol, and triglycerides to rise. Even subclinical or borderline hypothyroidism can cause high cholesterol. Two Chinese studies, for example, found that having a thyroid stimulating hormone (TSH) level in the upper end of the reference range makes you more likely to have a high cholesterol level. (Conversely, hyperthyroidism can cause unusually low cholesterol levels that are not linked to diet.)

If you do not have a diagnosed thyroid problem, high cholesterol levels are supposed to automatically trigger screening for hypothyroidism, according to many medical guidelines. Doctors are also advised to test thyroid function before prescribing any cholesterol-lowering medications. Unfortunately, this does not happen consistently, and many people with undiagnosed hypothyroidism are given cholesterol-lowering medication without any thyroid screening.

The take home message? It’s especially important for you to ask your physician to do a comprehensive thyroid evaluation, including, at minimum, a TSH test. If you are borderline or overtly hypothyroid, your next step is thyroid hormone replacement therapy.

Proper thyroid diagnosis and treatment of your hypothyroidism could resolve your high cholesterol and allow you to avoid taking prescription medication. One recent study found that more than 60 percent of people with high cholesterol and untreated hypothyroidism saw their cholesterol levels normalize once hypothyroidism was treated.

Research shows that a period of four to six weeks of thyroid hormone replacement therapy is usually needed to correct cholesterol levels in someone with hypothyroidism. Your healthcare provider should run a repeat cholesterol panel after that time to evaluate how your cholesterol levels respond to thyroid treatment.

Note, however, that research has shown that levothyroxine treatment for hypothyroidism may not fully restore cholesterol levels to normal. You may benefit from combination treatment that includes the T3 hormone, or you may need additional treatment targeted at your cholesterol levels.

If you are already diagnosed with hypothyroidism, it’s important that you also have cholesterol levels screened regularly, because you are at an increased risk of having elevated cholesterol. One study found that 56 percent of patients with hypothyroidism had high cholesterol, and 34 percent had both high cholesterol levels, and high triglycerides.

If you are being treated for hypothyroidism and are diagnosed with high cholesterol levels, your next step is to ensure that your thyroid treatment is optimized. You can read more about optimal hypothyroidism treatment, but to summarize, it’s typically treatment that safely resolves symptoms, and results in the following thyroid test results:

  • A TSH level of 2.5 or less

  • A free thyroxine (Free T4) level in the top half of the reference range

  • A free triiodothyronine (Free T3) level in the top half of the reference range

Lifestyle changes to help high cholesterol

If you still have cholesterol issues after your thyroid is optimally treated, there are dietary and exercise changes that may help get your cholesterol back into balance, and help you avoid the need for prescription medication. Specifically:

  • Substitute monounsaturated fats — such as olive oil — for saturated fat, choose leaner cuts of meat and poultry, and opt for lower-fat dairy products.

  • Eliminate trans fats — also known as “partially hydrogenated oils” —found in many processed foods and commercial baked goods.

  • Get enough omega-3 fatty acids, which help increase your HDL good cholesterol and reduce triglycerides. Salmon, walnuts, almonds, and flax seeds are all good sources. You can also add an omega-3 supplement.

  • Increase the soluble fiber in your diet. Soluble fiber comes from foods like oats, fruits, beans, and vegetables.

  • Get enough exercise. It can help raise your HDL good cholesterol and control your weight. Experts recommend around 30 minutes per day of moderate-intensity exercise.

Natural supplements

There is evidence that some supplements, including psyllium fiber supplements, artichoke extract, fish oil, niacin, red yeast rice, policosanols, plant stanols and sterols, and whey protein may help control your high cholesterol. Consult with a naturopathic physician for guidance on using supplements as part of a natural approach to lower cholesterol.

Prescription treatments for cholesterol

If your LDL cholesterol is still too high, your doctor may recommend adding a prescription drug to lower the LDL. There are three popular categories of cholesterol-lowering drugs.

Statin drugs, which lower LDL and triglycerides, and slightly raise HDL. Statins include:

  • Atorvastatin (Lipitor)

  • Fluvastatin (Lescol)

  • Lovastatin

  • Rosuvastatin (Crestor)

  • Simvastatin (Zocor)

  • Pitavastatin (Livalo)

  • Pravastatin (Pravachol)

Statin drugs have a number of risks and side effects, including memory loss, confusion, high blood sugar, type 2 diabetes, muscle pain and weakness, insomnia, headache, digestive problems, muscle inflammation and damage (called rhabdomyolysis), and (rarely) the potential to cause kidney failure.

ecause statin drugs can reduce your coenzyme Q10 (CoQ10) levels, some experts recommend taking a CoQ10 supplement along with statin drugs to reduce your risk of any muscle-related side effects.

Niacin/vitamin B-based drugs, which lower LDL and raise HDL. These drugs include Niaspan and Nicoar. Side effects include itching, tingling, headaches, and flushing.

Bile acid drugs, which cut down on cholesterol production. These drugs include Colestipol (Colestid), Cholestyramine (Prevalite), Colesevelam (WelChol), and Ezetimibe (Zetia). Side effects include constipation, gas, bloating, nausea, diarrhea, and muscle pain.

Mary Shomon
Meet Our Writer
Mary Shomon

Mary Shomon is a patient advocate and New York Times bestselling author who empowers readers with information on thyroid and autoimmune disease, diabetes, weight loss and hormonal health from an integrative perspective. Mary has been a leading force advocating for more effective, patient-centered hormonal healthcare. Mary also co-stars in PBS’ Healthy Hormones TV series. Mary also serves on HealthCentral’s Health Advocates Advisory Board.