The effects of thyroxine replacement on the levels of serum asymmetric dimethylarginine (ADMA) and other biochemical cardiovascular risk markers in patients with subclinical hypothyroidism

Summary Background The relationship between subclinical hypothyroidism (SH) and cardiovascular disease (CVD) is still under debate. The purpose of the present study was to evaluate plasma total homocysteine (tHcy), high sensitive C‐reactive protein (hsCRP), small dense low‐density lipoprotein (sdLDL), l‐arginine and asymmetric dimethylarginine (ADMA) concentrations and their relationship to nitric oxide (NO) production, measured as plasma nitrite‐plus‐nitrate (NOx) concentration, in patients with SH before and after thyroxine replacement therapy and compared with control group values. Design Eighty‐four women with SH and 33 healthy women as controls matched to the patient group for sex, age and body mass index (BMI), were enrolled in this study. Lipoprotein profile, tHcy, hsCRP, sdLDL, ADMA, l‐arginine and NOx were measured in pre‐ and post‐treatment blood samples. Results The pretreatment total cholesterol (TC), LDL‐C, hsCRP, ADMA and l‐arginine levels were significantly higher and NOx levels were lower than in the control group. After treatment, hsCRP, ADMA and l‐arginine levels were significantly reduced and sdLDL and NOx levels were significantly increased. Conclusion The present study demonstrated an elevation of hsCRP and ADMA plasma levels of patients with SH associated with a reduction in NO production, which may contribute to some cardiovascular alterations. The elevated ADMA and hsCRP levels were reduced after thyroxine replacement. Also the sdLDL levels of SH patients were found to be lower than the control group values whereas TC and LDL were elevated. Even though we found an elevation in sdLDL levels after treatment, those values were still not higher than in the control group.