Thyroid Disease and Cholesterol

Dr. Kang Health Pro
  • I recently saw a young woman in my clinic that was referred for treatment of a severely abnormal lipid profile.  Her total cholesterol was very high at greater then 270mg/dl, and in particular her LDL was quite elevated and her HDL was marginally low.  She had no prior medical issues, and her family history was quite unremarkable.


    One thing she kept complaining about was fatigue, lethargy, and constipation.  She had gained some weight over the past year but would still not be considered obese.  Her blood tests showed that she was markedly hypothyroid, and thyroid replacement hormone had just been started a couple of weeks ago by her primary care doctor.  The question from the referring doctor was what other cholesterol medicines does she need now?

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    The answer really relates to how the thyroid influences cholesterol levels.  The thyroid gland (located in the front of your neck) produces vital thyroid hormone that is very important in regulating your body’s metabolism.  One key effect of this hormone on cholesterol is that it helps prime the liver to breakdown circulating cholesterol.  It also stimulates other enzymes to clear triglycerides from the body.


    Several diseases can cause the thyroid gland to fail.  Most commonly in the US, an autoimmune reaction damages the thyroid.  When the thyroid gland is sufficiently injured, thyroid hormone levels fall.  Consequently, LDL and triglycerides level rise.  HDL levels seem not to be as significantly influenced by the lack of thyroid hormone.


    In one report, abnormal lipid levels can be found in more than 90% of people with overt or silent hypothyroidism.  Silent hypothyroidism is a condition in which a person may not have any significant symptoms of low thyroid levels but the blood tests are partially abnormal.  About 5-10% of people with high cholesterol will be found to have some abnormality in thyroid levels.


    One might then assume that people with hypothyroidism are at an increased risk of a heart attack.  However, studies are conflicting and the evidence of a direct relationship between the two is not that definite.  In any event, screening for hypothyroidism through a blood test is recommended for all people who have been diagnosed with high cholesterol.


    Treatment for hypothyroidism involves taking thyroid replacement hormone in the form of a pill.  Replacement hormone can improve significantly lipid levels.  The catch, which applies directly to this young woman I saw, is that it takes several months to see an improvement…sometimes as long as 4 months.  During that time, blood tests are used to gauge whether enough replacement hormone is being taken.


    So, my answer to the referring physician and the patient is that we need to wait a few months and repeat the lipid test.  Hopefully during that time, she will feel better and be more likely to exercise.  If the repeat lipid test is abnormal, then other measures which may include medicines may be needed.  Unfortunately, replacing the thyroid hormone alone is often not enough to bring lipid levels back to desirable levels.

Published On: May 15, 2007