Mean platelet volume in patients with subclinical hypothyroidism.

Subclinical hypothyroidism (SCH) is frequently encountered in the general population. Since it is generally asymptomatic, these patients are mostly identified through routine screening or evaluation of non-specific symptoms. It has been suggested as a risk factor for cardiovascular disease. On the other hand, mean platelet volume (MPV), which is a determinant of platelet function, is an independent risk factor for cardiovascular disease. The aim of this study was to evaluate MPV values in subclinical hypothyroidic patients when they were subclinical hypothyroidic and became euthyroidic after 12 weeks of levothyroxine replacement therapy. Sixty patients with subclinical hypothyroidism and 78 euthyroid healthy subjects matched for age, gender and body mass index were enrolled in the study. None of the study subject had diabetes, hypertension or dyslipidemia. All the study subjects were evaluated by biochemical and platelet parameters. Subclinical hypothyroidic patients were then reevaluated with the same parameters when they became euthyroid after 12 weeks of levothyroxine treatment. Platelet counts and metabolic parameters, except serum triglyceride and high density lipoprotein cholesterol (HDLC) levels, were similar between the two groups. Serum triglyceride and MPV values were significantly higher (pTG=0.007 and pMPV<0.001) while HDLC levels were lower (pHDLC=0.008) in the subclinical hypothyroidic group. MPV was found to be correlated with only antithyroid peroxidase (anti-TPO) antibody levels (P<0.001). MPV values were decreased after subclinical hypothyroidic patients became eythyroid. However, post-treatment MPV values were still higher (p=0.035) in the patient group than in control group. These results suggest that subjects with SCH are susceptible to increased platelet activation and increased MPV values which contribute to increased risk of cardiovascular complications.