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High-normal TSH levels tied to all-cause mortality
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In adults with euthyroidism, the risk for all-cause mortality, cardiovascular mortality and cancer mortality was increased among those with high-normal thyroid-stimulating hormone levels, study data show.
Kosuke Inoue, MD, of the Endocrinology and Diabetes Center, Yokohama Rosai Hospital in Japan, and colleagues evaluated data from National Health and Nutrition Examination Survey III (1988-1994) on 12,584 adults (mean age, 45.4 years; 48.6% men) in the United States to determine the relationship between low-normal thyroid function and all-cause or cause-specific mortalities. Follow-up was conducted for a median of 19.1 years.
Participants were divided into groups based on their TSH concentrations: 0.39 mIU/L to 1.15 mIU/L (low-normal TSH group), 1.16 mIU/L to 1.89 mIU/L (medium-normal TSH group) and 1.9 mIU/L to 4.6 mIU/L (high-normal TSH group).
Through follow-up, there were 3,395 all-cause deaths, including 1,048 CV deaths, 730 cancer deaths and 1,617 deaths from other causes.
Compared with the medium-normal TSH group, the high-normal TSH group (HR = 1.27; 95% CI, 1.1-1.47) and the low-normal TSH group (HR = 1.17; 95% CI, 1.02-1.35) had increased risk for all-cause death. The high-normal TSH group had a higher risk for CV death (HR = 1.3; 95% CI, 1.02-1.67) or cancer death (HR = 1.43; 95% CI, 1.01-2.01) compared with the other two groups.
The risk for all-cause mortality was significantly higher for men in the high-normal TSH group (HR = 1.29; 95% CI, 1.06-1.58) and men in the low-normal TSH group (HR = 1.32; 95% CI, 1.08-1.61) compared with men in the medium-normal TSH group. The risk for all-cause mortality was higher among women in the high-normal TSH group compared with women in the other two groups (HR = 1.24; 95% CI, 1.05-1.46).
In participants younger than 60 years, the risk for all-cause mortality was higher in the high-normal TSH group (HR = 1.49; 95% CI, 1.19-1.86) and the low-normal TSH group (HR = 1.29; 95% CI, 1.03-1.6) compared with the medium-normal TSH group. The high-normal TSH group had a higher prevalence of metabolic syndrome compared with the medium-normal TSH group (OR = 1.22; 95% CI, 0.96-1.55).
“The results of the present study indicate that high-normal TSH levels are associated with an increased risk of all-cause, CV and cancer mortality over a long-term period in U.S. adults,” the researchers wrote. “Furthermore, low-normal TSH levels were found to be associated with increased all-cause mortality. As differences in TSH levels within the current ‘normal’ range may affect long-time mortality, re-evaluation of the reference range of TSH levels may be required.” – by Amber Cox
Disclosure: The researchers report no relevant financial disclosures.
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