The role of subclinical hypothyroidism in lipid metabolism disorders

Abstract

Subclinical hypothyroidism is common in general practice. The clinical significance of latent thyroid dysfunction has not yet been determined. The parameters of lipid metabolism and oxidative stress were studied in patients suffering from subclinical hypothyroidism between the ages of 18 and 50 years. They had a level of thyroid stimulating hormone ≥4 mIU/l, the level of free thyroxine was normal. The control group consisted of healthy individuals with thyroid-stimulating hormone level of 0,4-2,4 mIU/l. Thyroid status, thyroid peroxidase antibodies, lipid profile, malondialdehyde-modified low-density oxidized lipoproteins, antibodies to low-density oxidized lipoproteins, homocysteine were determined for all individuals. With the repeated determination of thyroid-stimulating hormone in 16,8% patients spontaneous recovery of thyroid-stimulating blood hormone level was observed, which was associated with lower values of thyroid-stimulating hormone and the absence of thyroid peroxidase antibodies. In the group of patients with thyroid stimulating hormone levels ≥7 mIU/l, the total cholesterol level was significantly (p=0,02) higher than in the control group. In patients with elevated values of malondialdehyde-modified oxidized low-density lipoprotein, thyroid stimulating hormone level of ≥7 mIU/l was more frequently detected. A negative correlation was found between the level of IgG antibodies to low-density oxidized lipoproteins and the concentration of free thyroxin. In the control group, the correlation was found between the concentration of IgG antibodies to low-density oxidized lipoproteins and the level of thyroid-stimulating hormone. In the group of subclinical hypothyroidism, the concentration of homocysteine was significantly (p=0,01) higher in men. In patients with subclinical hypothyroidism, more often hyperhomocysteinemia was detected compared with the control group. The results suggest that subclinical hypothyroidism is associated with initial changes in the metabolism of lipids and homocysteine.