What's the connection between an underactive thyroid, cholesterol, and blood sugar levels?
Ask the doctor
Q. What role does low thyroid hormone play in high blood sugar and cholesterol?
A. Low thyroid hormone production by the thyroid gland (hypothyroidism) can cause a significant elevation in blood cholesterol levels. The relationship between blood sugar levels and thyroid hormone is not as straightforward.
Untreated hypothyroidism causes a rise in total cholesterol and especially LDL ("bad") cholesterol. Treatment with levo-thyroxine or other thyroid medication will lower cholesterol levels. But even with adequate treatment of the thyroid condition, there may be other reasons for your cholesterol to remain above normal, such as diet and genetic factors.
The relationship between blood sugar and thyroid hormone depends on the underlying conditions you may have. For example, if high blood sugar is related to type 1 diabetes, the person is more likely to also have an underactive thyroid gland and low thyroid hormone.
Most cases of type 1 diabetes and hypothyroidism have a similar cause - an autoimmune reaction. Your body produces antibodies that attack the pancreas and thyroid gland. The pancreas stops making insulin and blood sugar goes up. The damaged cells in the thyroid gland can't produce thyroid hormone.
Work with your doctor to get your thyroid blood level into the normal range and keep it there. It should then be easier to control blood sugar levels with diet, exercise, and medications.
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About the Author
Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing
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