TSH ≥2.5 mIU/l is Associated with the Increased Oxidative Damage to Membrane Lipids in Women of Childbearing Age with Normal Thyroid Tests.

According to current recommendations, a TSH value of <2.5 mIU/l should be maintained during preconception and pregnancy. The same recommendation, however, does not relate to all women of childbearing age. The aim of the study was to evaluate relationship between lipid peroxidation (LPO; index of oxidative damage to membrane lipids) and thyroid tests and other parameters, which may be affected by thyroid dysfunction, in euthyroid women of childbearing age. Ninety nine female inpatients with normal thyroid tests (TSH 0.27-4.2 mIU/l), aged 18-48 years, were prospectively enrolled. Blood concentrations of malondialdehyde+4-hydroxyalkenals (LPO index) were measured spectrophotometrically. Thyroid tests (TSH, FT4, FT3), thyroid antibodies and other laboratory parameters [cholesterol, HDL cholesterol (HDLC), LDL cholesterol, HDLC/cholesterol ratio, triglycerides, glucose, CRP, iron] were measured with standard methods. Blood LPO level was higher in women with TSH≥2.5 mIU/l than in women with TSH<2.5 mIU/l. Positive correlation was found between TSH concentration and LPO level (r=0.210, p=0.037). In the univariate regression analysis, blood LPO level did constitute the only independent factor associated with TSH≥2.5 mIU/l. Abnormal HDLC/cholesterol ratio occurred more frequently in subjects with TSH≥2.5 mIU/l. Additionally, LPO level correlated positively with triglyceride concentration (r=0.340, p=0.001), whereas it correlated negatively with HDLC concentration (r=-0.335, p=0.001) and with HDL/cholesterol ratio (r=-0.331, p=0.001). In conclusion, in women of childbearing age with normal thyroid tests, TSH≥2.5 mIU/l is associated with higher oxidative damage to membrane lipids and less favorable lipid profile, which supports our standpoint that TSH of less than 2.5 mIU/l should be maintained in all women of childbearing age.