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Thyroid hormone has multiple effects on cholesterol synthesis and metabolism
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American Thyroid Association Spring Symposium
Thyroid hormone may have a beneficial role in the treatment of cholesterol in hypothyroid patients, said Elizabeth N. Pearce, MD, MSc.
Treatment with thyroid hormone has multiple effects on cholesterol synthesis and metabolism, according to Pearce, assistant professor of medicine, section of endocrinology, diabetes and nutrition, Boston University School of Medicine.
However, clinical lipid effects are more pronounced in overt hypothyroidism than subclinical hypothyroidism, she said. Previous data indicated that levothyroxine significantly decreases total cholesterol and LDL in patients with overt hypothyroidism. In contrast, lipid effects among patients with subclinical hypothyroidism are more pronounced with thyroid-stimulating hormone <12, Pearce said.
Smoking, insulin resistance, BMI, age and sex may modify the effect of thyroid status on lipids.
According to Pearce, there are two emerging risk markers to watch. Oxidized LDL has been identified as a risk factor for atherosclerotic diseases, such as coronary heart disease and stroke. Results of small studies have indicated that oxidized LDL is increased in patients with both overt and subclinical hypothyroidism. However, published studies of oxidized LDL and thyroid hormone are small and uncontrolled.
The second emerging risk marker is apolipoproteins, especially ApoB. Previous data also indicated that levothyroxine was successful in reducing mean levels of ApoB in patients with both overt and subclinical hypothyroidism, although the effect was more significant in overt hypothyroidism. – by Katie Kalvaitis
It is interesting because when you look at the lipid problems, there is a great tendency to quite rightly screen for lipids and treat them. What was not said during this presentation is that some of these lipid abnormalities can be due to the thyroid, and they will correct themselves when the thyroid is corrected. 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 for the average clinician to appreciate that.
– John H. Lazarus, MA, MD
Emeritus Professor, Clinical Endocrinology,
Cardiff
University School of Medicine, Wales
It is important to consider cost-effective treatments. If I am presented with the choice between normalizing the thyroid function of a patient at the cost of about 15 to 20 cents per day with a single thyroid hormone replacement tablet or $2.50 per day with a cholesterol-lowering drug, obviously I want to treat the thyroid disease first to see whether, in fact, additional cholesterol-lowering treatment is needed.
– Irwin L. Klein, MD
Associate Chairman of Medicine,
North Shore University Hospital, New York, and
Associate Program Director for Education in the General Clinical Research Unit
For more information:
- Pearce EN. Lipid alterations in subclinical and overt hypothyroidism. Presented at: the American Thyroid Association Spring Symposium; March 28, 008; Washington.