Douglas S. Ross, MD

ABSTRACT: Subclinical hypothyroidism is associated with elevated low-density lipoprotein (LDL) cholesterol levels and several factors related to atherosclerosis, including increased C-reactive protein levels and impaired endothelium-dependent vasodilatation. However, considerable controversy exists about screening for and treating this thyroid disorder. Thyroxine therapy lowers elevated LDL cholesterol levels in patients whose serum thyroid-stimulating hormone (TSH) concentrations are higher than 10 mIU/L ; thus, most experts recommend treatment for such patients. However, there is no consensus regarding the management of patients with TSH levels of less than 10 mIU/L. Although the evidence supporting treatment of these patients is not compelling, it is reasonable to offer a therapeutic trial of thyroxine to those who have symptoms.

The optimal approach to subclinical hypothyroidism continues to be debated. Experts disagree over screening for thyroid dysfunction, the threshold TSH level for treatment, and the upper limit of normal of the TSH reference range.