Is Hypothyroidism Linked to High Cholesterol?

Learn more about the well-established link between thyroid disease and high cholesterol.
Is Hypothyroidism Linked to High Cholesterol?

You may remember that talk about cholesterol was all the rage in the early 2000s. Cholesterol is bad bad bad, they said. Try the South Beach or Atkins or Ornish diet. 


But what is cholesterol? Is it really bad? (In this case, maybe.) And how is it linked to hypothyroidism? 


What Is Cholesterol? 


Cholesterol is a waxy substance that the body needs to build cells. It comes from two sources: the liver and daily oral intake. Your liver makes all the cholesterol that the body needs. 


Additional cholesterol comes from food, such as meat, poultry, and dairy products. Foods that are high in saturated and trans saturated fats cause the liver to produce more cholesterol. These added fats from dietary intake are what cause cholesterol levels to rise. 


Two main types of cholesterol are typically monitored: low-density lipoprotein (LDL) and high-density lipoprotein (HDL). Too much LDL or too little HDL may increase the risk of cholesterol building up in the inner walls of the arteries. If cholesterol builds up in the arteries, it can form a thick, hard plaque that makes the arteries narrow and less flexible. Ultimately, this buildup could lead to a heart attack or stroke.


It is recommended to keep LDL levels below 100 mg/dL. A level above 130 mg/dL could greatly increase your health risk. HDL should be above 60 mg/dL to improve heart function and reduce cardiovascular disease. Numbers below 40 mg/dL in men and 50 mg/dL in women may put them at an increased risk for disease. Total cholesterol level should remain under 200 mg/dL.


Screening for cholesterol levels is based on sex, age, and cardiac risk factors. There is some controversy on the best age to start screening. In general, it is best to initiate screening in men between ages 20-25, especially for those who have high risk in regard to cardiac risk factors. For women, it’s suggested that screening be initiated between ages 30-35. For those with a lower risk, men can begin screening at 35 and women at 45.


What is the link between the thyroid and cholesterol?


The thyroid is a very important gland in our bodies that releases hormones to help control metabolism. The hormones that the thyroid releases help in regulating our breathing, heart rate, body weight, muscle strength, body temperature, menstrual cycles in women, nervous system, and more. When the thyroid is not producing the correct number of hormones that we need, our bodies may feel out of whack, producing a host of symptoms.


One of the most important systems that the thyroid affects is the body’s ability to metabolize, causing poor processing of cholesterol. As the body changes and slows with an underactive thyroid, the body’s inability to break down LDL may also slow, causing cholesterol to continue to build up. 


There is a linear relationship seen with cholesterol and Thyroid Stimulating Hormone (TSH) levels. The higher the TSH, the higher the LDL and the lower the HDL. Even when TSH is in the normal range, but on the upper limits of normal, cholesterol may be mildly elevated.


The inability of the body to properly metabolize cholesterol in hypothyroidism predisposes patients to the risk of heart disease. Thyroid disease not only increases cholesterol levels, but also leads to hypertension and the stiffening of major blood vessel walls, which all lead to increased cardiac disease risk. 


Even with subclinical hypothyroidism, where the TSH is slightly elevated and Free T4 is within normal range, an increased risk of cardiac disease has been shown.


How can we control cholesterol levels?


Having hypothyroidism is not something we can control, so it may seem unfair that you also have to worry about having high cholesterol and an increased risk for cardiac related disease. Luckily, just as cholesterol is elevated with low thyroid function, once the thyroid is treated with appropriate hormone replacement, the cholesterol levels will likely fall.


Research shows that in 60% of people with a new diagnosis of hypothyroidism and high cholesterol, their elevated cholesterol levels resolve after thyroid function is restored. At least 75% of people who are treated with levothyroxine are able to go without cholesterol-lowering medications within one year after diagnosis.


In some cases, cholesterol levels may remain high, even after treatment with levothyroxine. These patients might try eating a nutrient-rich diet and exercising to reduce cholesterol levels. If this is not enough, cholesterol-lowering medications may need to be started with the supervision of your doctor in order to avoid cardiac disease. 


As always, it’s important to discover the root cause before treatment is started. If you have elevated cholesterol on routine laboratory tests, talk to your provider about checking your thyroid function before taking cholesterol-lowering medications. Too many people go years without a clinical or subclinical hypothyroid diagnosis, leading to cardiac and other problems throughout the body.


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