Relationship of thyroid hormone levels and cardiovascular events in patients with type 2 diabetes

Alterations in thyroid hormone levels are found associated with inflammation in patients with non-thyroidal illness (NTIS) and are common in patients with type 2 diabetes mellitus (T2DM). Inflammation has also been linked with development of cardiovascular events (CVE) in T2DM. Our objective was to assess whether thyroid hormone abnormalities typical of NTIS in patients with T2DM are related to inflammation and CVE. This was a cross-sectional study of 140 subjects; 70 with T2DM and 70 as a control group paired by age, sex and body mass index (BMI). We recorded age, sex, BMI, waist/hip ratio, diabetes duration, HbA1c, CVE history, serum amyloid A (SAA), TSH, total (T) and free (F) T4 and T3, reverse T3 (rT3) and TT3/rT3 ratio. Patients with T2DM had lower levels of TT4 (p = 0.012), TT3 (p < 0.001), FT3 (p < 0.001) and TT3/rT3 (p = 0.002). They also showed higher FT4 (p < 0.001) and similar TSH levels (p = 0.627) compared to the control group. SAA levels correlated positively with rT3 (r = 0.45; p < 0.001) and inversely with TT3/rT3 (r = -0.38; p = 0.001). Patients with T2DM and history of CVE had higher rT3 (p = 0.006) and lower TT3/rT3 (p = 0.002), along with higher SAA levels (p = 0.002) than patients without this characteristic. Multiple logistic regression showed that factors independently associated with CVE were older age (OR = 1.159, 95 % CI 1.011-1.329), male sex (OR = 4.391, 95 % CI 1.081-17.829) and higher TT3/rT3 (OR = 0.993, 95 % CI 0.987-0.999). We have confirmed the presence of NTIS in T2DM. We also showed that thyroid hormone abnormalities are associated to inflammatory activity and to CVE in these patients.