Hashimoto thyroiditis is an independent cardiovascular risk factor in clinically hypothyroid patients

Hypothyroidism is a common disorder that confers an increased cardiovascular risk. The most common cause is Hashimoto thyroiditis (HT) but it can also be caused by thyroidectomy and radioiodine therapy. The aim of the study is to examine whether there is a relation between the cause of hypothyroidism and cardiovascular risk. Subjects and methods: The study included 20 patients with Hashimoto thyroiditis and hypothyroidism, 20 patients with post-thyroidectomy hypothyroidism, 20 patients with post-radioiodine hypothyroidism, and 20 age and sex matched controls. In all the studied subjects we determined thyroid function tests; TSH and F.T4, thyroid auto-antibodies; anti-TPO and anti-TG antibodies, carotid intima media thickness (CIMT), flow mediated dilation (FMD) and serum nitric oxide. Results: CIMT showed a trend to be higher in HT group (0.93± 0.08 mm) compared to other causes of hypothyroidism (P = 0.090). Multivariate analysis showed that HT is an independent predictor of CIMT (P = 0.015). FMD was significantly lower in HT group (5.74± 1.33%) compared to post-thyroidectomy (7.16± 1.05%) (P = 0.001), and post-radioiodine therapy (7.34 ±1.34%) (P = 0.000). Multivariate analysis showed that HT is an independent predictor of FMD (P =0.000). NO was significantly higher in hypothyroid patients (125.98 ± 5.03 lM/ml) compared to controls (39.44± 3.63 lM/ml) (P =0.001), both univariate and multivariate analyses showed that NO is an independent predictor of both CIMT and FMD (P = 0.000). Conclusion: To our knowledge, this is the first study to show that Hashimoto thyroiditis is an independent cardiovascular risk factor in clinically hypothyroid patients.