The production of thyroid hormone

Hypothyroidism, a disease characterized by a decrease in the production of thyroid hormone, is hypothesized to increase the risk of cardiovascular disease (CVD).  In a follow-up study of 1,000 men aged 55 years and older, the investigators are interested in the potential impact of subclinical hypothyroidism on the incidence of myocardial infarction. The overall cumulative incidence of CVD in this cohort was 1.8%. The cumulative incidence of CVD was 12.8% among the 47 men with subclinical hypothyroidism and 1.3% among men without hypothyroidism. The overall prevalence of subclinical hypothyroidism in the cohort was 4.7%.

Q: Assuming causality, what proportion of CVD in men aged 55 and above with subclinical hypothyroidism can be prevented by treating all men with subclinical hypothyroidism with thyroid hormone replacement therapy? Calculate the etiologic fraction among the exposed.