Subclinical Hypothyroidism and Cardiac Risk: Lessons from a South Indian Population Study

The benefits of treating subclinical hypothyroidism are currently under debate, prevention of adverse cardiac events purporting to be one of the main benefits. The effect of subclinical hypothyroidism on the cardiovascular health of the Indian sub-population is largely unknown. This study was designed to examine these effects and to help guide treatment of this disorder.

A cross-sectional adult population survey was carried out in urban coastal area of central Kerala. 986 volunteers underwent complete biochemical and physical examinations, 110 were found to have subclinical hypothyroidism (8.9%). The ten-year risk of an adverse cardiac event, was calculated using the Framingham score algorithm. Eligible subclinical hypothyroid subjects (N = 110) and a randomly selected, age and gender matched control group (N = 220) were compared.

This population was found to have high baseline levels of diabetes 19.5%, hypercholesterolemia 57.2% and systolic hypertension 24.6%. No association was found between subclinical hypothyroid status or rising TSH and Framingham 10-year risk. While no difference between groups was noted with respect to lipid profile, a rising TSH was found to be significantly correlated with mild worsening of the lipid profile. A significant positive correlation was found between skinfold thickness and TSH.

Subclinical hypothyroidism is not a contributing factor to elevated Framingham risk in this population, and while a mild effect was observed on the lipid profile, its effect is unlikely to be clinically relevant. We hypothesize that in this population a genetic component may be responsible for the uniquely high rates of metabolic syndrome and other endocrine diseases.