Study of the alterations of total plasma homocysteine levels and atherogenic lipid profile in hypothyroidism

ABSTRACT

Hypothyroidism is associated with increased cardiovascular morbidity, which cannot be fully explained by the atherogenic lipid profile observed in these patients. Elevation of total plasma concentrations of homocystein [t-Hcy] is an important and independent risk factor for cardiovascular disease. Because hypothyroidism decreases hepatic levels of enzymes involved in the remethylation pathway of homocystein, we prospectively evaluated fasting t-Hcy in hypothyroid patients before and after recovery of euthyroidism. In the current study we examined 40 patients with peripheral hypothyroidism [12 with autoimmune thyroiditis, 10 with Graves’ disease, [treated surgically 0r carbimazole], 2 with toxic multinodular goiter [treated surgically], 12 surgically resected goiter, and 4 with idiopathic hypothyroidism] in comparison with those of 25 hyperthyroid patients and 25 euthyroid control subjects with the same age and sex attending the outpatient and the inpatient departments of general surgery, Mansoura University Hospital. In all cases, a detailed medical history was obtained and a thorough physical examination was performed with emphasis on the presence of symptoms / signs indicative of underlying thyroid disorders. In addition to plasma lipid parameters, thyrotropin [TSH], T3, T4 and t-Hcy levels were measured in a fasting blood samples. Fasting t-Hcy levels were higher in patients with hypothyroidism in comparison with those of hyperthyroid patients and euthyroid control subjects. Plasma t-Hcy in hypothyroidism was significantly correla ted with high TSH and lipoprotein [a] levels [r = 0.306, P = <0.01 and r = 0.476, P = <0.001, respectively]. The restoration of euthyroid state with levothyroxine therap [75 ug/day] was followed by a significant improvement of plasma lipid profile. Also, thyroid hormone replacement significantly decreased fasting t-Hcy. We confirmed the observation of hyperhomocysteinemia in hypothyroidism, which together with the elevated plasma lipoprotein [a] may contribute to an accelerated atherogenesis in these patients. As hypothyroidism may be a treatable cause of hyperhomocysteinemia, and as fasting t-Hcy is associated with a significant increased relative risk of coronary artery disease, measurement of t-Hcy to screen this dynamic association of cardiovascular riskfactors during hypothyroidism may be of interest