CONTEXT: Hyperthyroidism and hypothyroidism, both overt and subclinical, are associated with all-cause and cardiovascular mortality. The association between thyroid hormones and mortality in euthyroid individuals, however, is unclear.
OBJECTIVE: To examine the prospective association between thyroid hormones levels within normal ranges and mortality endpoints.
SETTING AND DESIGN: A prospective cohort study of 212 456 middle-aged South Korean men and women who had normal thyroid hormone levels and no history of thyroid disease at baseline from January 1, 2002 to December 31, 2009. Free T4 (FT4), free T3 (FT3), and TSH levels were measured by RIA. Vital status and cause of death ascertainment were based on linkage to the National Death Index death certificate records.
RESULTS: After a median follow-up of 4.3 years, 730 participants died (335 deaths from cancer and 112 cardiovascular-related deaths). FT4 was inversely associated with all-cause mortality (HR = 0.77, 95% confidence interval 0.63-0.95, comparing the highest vs lowest quartile of FT4; P for linear trend = .01), and FT3 was inversely associated cancer mortality (HR = 0.62, 95% confidence interval 0.45-0.85; P for linear trend = .001). TSH was not associated with mortality endpoints.
CONCLUSIONS: In a large cohort of euthyroid men and women, FT4 and FT3 levels within the normal range were inversely associated with the risk of all-cause mortality and cancer mortality, particularly liver cancer mortality.
OBJECTIVE: Overt and subclinical hypothyroidism are risk factors for atherosclerosis. It is unclear whether thyroid hormone levels within the normal range are also associated with atherosclerosis measured by coronary artery calcium (CAC).
APPROACH AND RESULTS: We conducted a cross-sectional study of 41 403 apparently healthy young and middle-aged men and women with normal thyroid hormone levels. Free thyroxin, free triiodothyronine, and thyroid-stimulating hormone levels were measured by electrochemiluminescent immunoassay. CAC score was measured by multidetector computed tomography. The multivariable adjusted CAC ratios comparing the highest versus the lowest quartile of thyroid hormones were 0.74 (95% confidence interval, 0.60-0.91; P for trend <0.001) for free thyroxin, 0.81 (0.66-1.00; P for trend=0.05) for free triiodothyronine, and 0.78 (0.64-0.95; P for trend=0.01) for thyroid-stimulating hormone. Similarly, the odds ratios for detectable CAC (CAC >0) comparing the highest versus the lowest quartiles of thyroid hormones were 0.87 (0.79-0.96; P for linear trend <0.001) for free thyroxin, 0.90 (0.82-0.99; P for linear trend=0.02) for free triiodothyronine, and 0.91 (0.83-1.00; P for linear trend=0.03) for thyroid-stimulating hormone.
CONCLUSIONS: In a large cohort of apparently healthy young and middle-aged euthyroid men and women, low-normal free thyroxin and thyroid-stimulating hormone were associated with a higher prevalence of subclinical coronary artery disease and with a greater degree of coronary calcification.
KEYWORDS: thyroid hormones; thyrotropin; thyroxine; triiodothyronine
The role of hepatitis virus infection in glucose homeostasis is uncertain. We examined the associations between hepatitis B virus (HBV) or hepatitis C virus (HCV) infection and the development of diabetes in a cohort (N = 439,708) of asymptomatic participants in health screening examinations. In cross-sectional analyses, the multivariable-adjusted odds ratio for prevalent diabetes comparing hepatitis B surface antigen (HBsAg) (+) to HBsAg (-) participants was 1.17 (95% CI 1.06-1.31; P = 0.003). The corresponding odds ratio comparing hepatitis C antibodies (HCV Ab) (+) to HCV Ab (-) participants was 1.43 (95% CI 1.01-2.02, P = 0.043). In prospective analyses, the multivariable-adjusted hazard ratio for incident diabetes comparing HBsAg (+) to HbsAg (-) participants was 1.23 (95% CI 1.08-1.41; P = 0.007). The number of incident cases of diabetes among HCV Ab (+) participants (10 cases) was too small to reliably estimate the prospective association between HCV infection and diabetes. In this large population at low risk of diabetes, HBV and HCV infections were associated with diabetes prevalence and HBV infection with the risk of incident diabetes. Our studies add evidence suggesting that diabetes is an additional metabolic complication of HBV and HCV infection.