Excess mortality in treated and untreated hyperthyroidism is related to cumulative periods of low serum TSH.

Excess mortality in treated and untreated hyperthyroidism is related to cumulative periods of low serum TSH.

J Clin Endocrinol Metab. 2017 Mar 28;:

Authors: Lillevang-Johansen M, Abrahamsen B, Jørgensen HL, Brix TH, Hegedüs L

Abstract
Introduction and Aim: Cumulative time-dependent excess mortality in hyperthyroid patients has been suggested. However, the effect of anti-thyroid treatment on mortality, especially in subclinical hyperthyroidism remains unclarified. We investigated the association between hyperthyroidism and mortality in both treated and untreated hyperthyroid individuals.
Patients and Methods: Register-based cohort study of 235,547 individuals who had at least one serum-TSH measurement in the period 1995-2011 (7.3 years median follow-up). Hyperthyroidism was defined as at least 2 measurements of low serum TSH. Mortality rates for treated and untreated hyperthyroid subjects compared to euthyroid controls were calculated using multivariate Cox-regression analyses, controlling for age, sex and comorbidities. Cumulative periods of decreased serum TSH were analyzed as a time-dependent covariate.
Results: Hazard ratio (HR) for mortality was increased in untreated [1.23 (95% CI: 1.12-1.37, p<0.001)], but not in treated hyperthyroid patients. When including cumulative periods of TSH in the Cox-regression analyses, HR for mortality per every 6 months of decreased TSH was 1.11 (95% CI: 1.09-1.13, p<0.0001) in untreated hyperthyroid patients (n=1137), and 1.13 (95% CI: 1.11-1.15, p<0.0001) in treated patients (n=1656). This corresponds to a 184% and 239% increase in mortality after 5 years of decreased TSH in untreated and treated hyperthyroidism, respectively.
Conclusion: Mortality is increased in hyperthyroidism. Cumulative periods of decreased TSH increased mortality in both treated and untreated hyperthyroidism, implying that excess mortality may not be driven by lack of therapy, but rather inability to keep patients euthyroid. Meticulous follow-up during treatment, in order to maintain biochemical euthyroidism, may be warranted.

PMID: 28368540 [PubMed - as supplied by publisher]

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