Hypothyroidism & Heart Health: Too Little Thyroid Hormone, Too Much Cholesterol

With Arjola Bano, MD, DSc and  Elizabeth N. Pearce, MD

Certainly, having a thyroid disorder is no picnic but understanding the ways in which your thyroid can affect how your body functions is an important first step toward feeling better. A growing body of research finds that both overt and subclinical hypothyroidism can put you at a greater risk for high blood cholesterol, a leading and controllable cause of cardiovascular disease.1

Fortunately, keeping your thyroid in balance will help keep your cholesterol in check. Even better: knowing your heart disease risk means you can be proactive with preventative measures so you’ll be helping improve your thyroid health while simultaneously staying heart-healthy.

Hypothyroidism like Hashimoto's thyroiditis can raise the risk of heart disease.Hypothyroidism like Hashimoto's thyroiditis may lead to increased risk for heart disease. Both require proper management.

Hypothyroidism and High Cholesterol: A Look at the Relationship  

Most of the cholesterol circulating in your blood is produced in your body, specifically the liver.  The body needs cholesterol to carry out all sorts of important functions, such as: strengthen cell membranes, make hormones, fat-soluble vitamin, and bile acids that are needed to help digest fat.  But like all good things, too much cholesterol can become a bad thing, even deadly. You may have heard that there are two types of cholesterol. The so-called bad cholesterol is known as low-density lipoprotein (LDL) and high-density lipoprotein, or HDL, is the kind of blood cholesterol you want more of since it is protective. Too much bad cholesterol or not enough good cholesterol typically leads to a buildup of the cholesterol plaque in the arteries, which raises your risk for heart disease and stroke.

So, what does this have to do with your thyroid? 

The effect of overt hypothyroidism on cholesterol has been well documented for years.  At an American Thyroid Association Symposium, John H. Lazarus, MD said, “There is a huge emphasis on lipid screening, and one cannot assume that all of this is just due to a rise in lipids for no obvious reason—you might be uncovering a thyroid problem. It is very important to appreciate that.”[2]

How does this work?  If you have hypothyroidism, your body isn’t making enough thyroid hormones, which can have a pretty major effect on cholesterol levels.  In an updated review in the Journal of Clinical Endocrinology and Metabolism, Elizabeth N. Pearce, MD, MSc, professor of medicine at Boston University School of Medicine in Massachusetts, details two major ways low thyroid hormones can lead to high cholesterol.3

First, thyroid hormones help regulate LDL cholesterol clearance.  Too little thyroid hormones, translate to less LDL-C receptors on cell surfaces, which translates to not enough cholesterol clearance and an increase in bad cholesterol, LDL. Second, low thyroid hormones may cause greater intestinal cholesterol absorption. The net effect is hyperlipidemia, a big word for high cholesterol.3

A team of scientists at Erasmus University in Rotterdam, Netherlands, led by Arjola Bano, MD, DSc, examined data of 9,420 patients enrolled in the in the Rotterdam Study for nearly nine years, looking at their levels of TSH, free thyroxine (fT4) and risk of heart disease or cerebrovascular disease.What they discovered is that as fT4 increases, the risk of developing heart disease is doubled, and there is an 87% greater risk of suffering from an atherosclerosis-related event such as heart attack or stroke.4 Atherosclerosis is a scientific term for heart disease.

According to Dr. Bano, “our findings suggest that thyroid hormone (fT4) measurement can help identify individuals at increased risk of atherosclerosis.”

Treatment Options for High Cholesterol with Hypothyroidism

For information about best treatment options, Dr. Pearce told EndocrineWeb, “In patients with both hypothyroidism and hyperlipidemia, the hypothyroidism should be treated first, and, for patients with optimally treated hypothyroidism who still require treatment for high cholesterol, the options are the same as those for patients with hyperlipidemia but without thyroid disorders.”

Also, it is possible, even more likely, to have overt hypothyroidism and primary hyperlipidemia, in which case both conditions should be treated separately, she said.

Hyperlipidemia can also be a considerable risk for people with subclinical hypothyroidism.  While there is less consensus regarding the treatment of high cholesterol in people who have subclinical hypothyroidism, several studies point to possible links.4,5

For example, Gabriela Brenta, MD, an associate professor of endocrinology and biochemistry at  Buenos Aires University in Brazil, reports that elevated thyroid stimulating hormone (TSH) levels are associated with an unfavorable lipid profile and suggests the need for thyroid hormone (T4) supplementation as a possible treatment.[3] This research was one of a series of studies making a connection between high TSH levels and elevated blood cholesterol in which a person’s TSH appears directly proportional to blood lipid levels—the higher the TSH, the higher person’s lipids, too.4 The primary factor driving this process is the cholesterol-synthesizing enzyme, HMGCR (3-hydroxy-3-methyl glutaryl-CoA reductase), which is targeted by the statin medications prescribed to lower blood cholesterol levels and reduce the risk of heart disease.

Hypothyroidism and Cholesterol: Should This Matter to Me?

First and foremost, you should discuss your thyroid status and any concerns you have about your cholesterol levels and cardiovascular health with your doctor, if you haven’t already. While the thyroid replacement medication, levothyroxine, is effective in reversing thyroid-related hyperlipidemia in overt hypothyroidism, there is a lack of consensus regarding whether or not to treat hyperlipidemia in patients with subclinical hypothyroidism. 

According to Dr. Pearce, “Treatment of subclinical hypothyroidism can be considered in patients with hyperlipidemia, particularly if there are other reasons to treat. For example, the presence of hypothyroid symptoms. However, there is currently not strong evidence for prescribing thyroid replacement in these patients otherwise.” 

Dr. Gabriel Brenta recommends treating with levothyroxine “in those patients with hypercholesterolemia and subclinical hypothyroidism (TSH between 5.5 and 10mU/L) provided they are below 65 years of age.” Her recommendation matches the Clinical Practice Guidelines for Hypothyroidism in Adults Cosponsored by the American Associate of Clinical Endocrinologists and the American Thyroid Association.6  Dr. Brenta and her team also recommend that levothyroxine replacement therapy may be considered for patients with persistently mildly elevated TSH levels and confirmed Hashimoto’s thyroiditis. 

Since thyroid hormones levels will affect individuals differently, it is important to talk with your doctor about the treatment options that will best support your health and lifestyle, taking into account all your medical risks, family history, and current thyroid status.

How to Address Your Concerns about Heart Disease with Hypothyroidism 

Certainly, the best approach is to be preventative. Here is where exercise can play a major role in helping to promote cardiovascular health. Walking an hour a day is great, and if you are up for something more intense, you might consider adding resistance training or a work-out with weights. Moderate intensity exercises, such as hiking, swimming or Zumba (a form of line dancing) have been shown to increase HDL levels, which will help counteract a higher LDL. The more active you are, and better chance you have to protect your heart and improve your cholesterol profile.

 Not ready to jump into weight training? No problem. If hypothyroidism hasn’t been making you feel tired, having high cholesterol also can impair your aerobic capacity, making exercise more difficult. But there’s good news from two population-based cohort studies that measured the benefits of low intensity walking versus moderate exercise.[REFS} Participants in the walking groups were more likely to complete the full 150 minutes of weekly exercise recommended by the Centers for Disease Control and Prevention, and they reported improvements in their physical well-being. The bottom line: Doing some type of physical activity for at least 20-30 minutes every day can advance your heart health. 

Remember, knowledge is power. Know your blood cholesterol numbers. Ask your doctor if you should be making any changes to your diet, level of physical activity, or medications, to improve your blood cholesterol. And, as always, keep track of your thyroid levels. If you have any form of hypothyroidism, practice a heart healthy lifestyle that includes staying active, following a heart healthy diet, and taking measures to reduce stress. Managing your hypothyroidism or thyroiditis doesn’t have to stop you from living your best life.


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