Background:Subclinical hypothyroidism (SH) is defined as elevated serum levels ofTSH with normal levels of free T4 (fT4) and free T3 (fT3). The prevalence of SH has been reported to be 4–10% in general population. Since it is generally asymptomatic, these patients are mostly identified through routine screening or evaluation of non specific symptoms. About 2–5% of patients progress to overt hypothyroidism annually. Objectives: To study the mean platelet volume in patients with subclinical hypothyroidism and to study the association between MPV and CAD in patients with subclinical hypothyroidism.