Subclinical Hypothyroidism and Metabolic Syndrome: A Common Association by Chance or a Cardiovascular Risk Driver?

The metabolic syndrome (MS) and subclinical hypothyroidism (SCH) are highly prevalent in the general population. Cross-sectional epidemiological data suggest that a mutual association exists between the two, although the cause-effect relationship remains poorly elucidated. As SCH raises cholesterol, blood pressure, and visceral fat, it is easy to understand why it associates with MS. Rather, the reasons whereby MS patients are at higher risk for SCH are less apparent. Some studies have reported that SCH is itself characterized by high cardiovascular risk. Therefore, the coexistence of SCH and MS may identify subjects at a particularly high risk for future cardiovascular events. Recent data published in Metabolic Syndrome and Related Disorders indicate that carotid intima-media thickness, a marker of initial atherosclerosis and a possible predictor of future events, is higher in patients with both SCH and MS than in the presence of each condition alone. In this Editorial, we discuss the clinical implications of SCH and MS association and the interpretation of such recent findings.