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Hypothyroidism is associated with unhealthy lipid levels. (Lipids are fat molecules, such as triglycerides and cholesterol.) Specifically, people with hypothyroidism and even subclinical (without symptoms) hypothyroidism are at higher risk for high total and LDL (the so-called "bad") cholesterol, triglycerides, and other lipid levels associated with heart disease. In fact, one study in 2000 indicated that hypothyroidism is second only to poor dietary habits as a cause of high, unhealthy cholesterol levels. Treatment of hypothyroidism with thyroid hormone replacement (such as levothyroxine sodium [Synthroid or Levoxyl]) can have a positive impact on cholesterol levels.
Medically reviewed by John A. Daller, MD; American Board of Surgery with subspecialty certification in surgical critical care
"Clinical manifestations of hypothyroidism"