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 or 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 correlated with high TSH and lipoprotein (a) levels (r = 0.306, P = <0.01 & 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 risk factors during hypothyroidism may be of interest.