Risk factors for cardiovascular disease in patients with subclinical hypothyroidism

INTRODUCTION: The relationship between subclinical hypothyroidism (SCH) and cardiovascular disease is not fully understood. We investigated risk factors for cardiovascular disease (lipid profile, lipoproteins, insulin resistance, C-reactive protein [CRP] homocysteine [Hcy] and fibrinogen levels) and their relationships with thyroid hormones in SCH patients and controls. METHODS: Thirty-eight SCH patients and 44 controls were enrolled in this study. No patients had any substantial confounding medical conditions (including diabetes mellitus or coronary heart disease) or were taking thyroid-related medication. RESULTS: Serum total cholesterol (P<0.05), low-density lipoprotein cholesterol (P<0.05) and triglycerides (P<0.001) were higher in patients with SCH than in controls. Serum lipoprotein(a) (Lp[a]) levels were higher in SCH subjects but this difference did not reach statistical significance (P=0.07). No significant differences were noted in CRP, Hcy, fibrinogen, high-density lipoprotein cholesterol, apolipoprotein A-1, apolipoprotein B (Apo B) or insulin resistance between patients with SCH and controls (in all cases, P>0.05). Free triiodothyronine (FT3) negatively correlated with Apo B (r=.0.46, P=0.005) and Lp(a) (r=.0.31, P=0.03) in patients with SCH and negatively correlated with Lp(a) (r=.0.30, P=0.04) in controls. All of these parameters were comparable between patients with thyroid-stimulating hormone (TSH) >10 microIU/ml and TSH <10 microIU/ml (in SCH patients, P>0.05). CONCLUSION: Our results suggest that SCH is associated with some lipid and lipoprotein abnormalities. Our results also suggest that this association does not depend on the subject's TSH level.