Abstract
BackgroundHyperthyroidism has been linked with different morbidities, like atrial fibrillation, stroke and diabetes mellitus. However, our knowledge regarding the extent and temporal relation between hyperthyroidism and other diseases is fragmented. Here, we aimed at evaluating various morbidities before and after the diagnosis of hyperthyroidism.MethodsObservational cohort study. From nationwide Danish health registers 2631 hyperthyroid singletons and 375 twin pairs discordant for hyperthyroidism were identified and followed for an average of 6 years (range 0–13). Data on the occurrence of cardiovascular diseases, lung diseases, diabetes mellitus, rheumatic diseases and malignant diseases was obtained by person-to-person record linkage with the National Danish Patient Register and/or the Danish National Prescription Registry (lung diseases and diabetes mellitus). Logistic and Cox regression models were used to assess the risk of morbidity before and after the diagnosis of hyperthyroidism, respectively. All Cox regression analyses were adjusted for the degree of co-morbidity preceding the diagnosis of hyperthyroidism, using the Charlson score.ResultsHyperthyroid individuals had a significantly higher risk of being diagnosed with cardiovascular diseases (odds ratio (OR) 1.65; 95% confidence interval (CI): 1.45–1.87), lung diseases (OR 1.53; 95% CI: 1.29–1.60), and diabetes mellitus (OR 1.43, 95% CI: 1.20–1.72), but not with malignant diseases (OR 1.16, 95% CI: 0.99–1.36) prior to the diagnosis of hyperthyroidism. After the diagnosis of hyperthyroidism, subjects had a significantly higher risk of being diagnosed with cardiovascular diseases (hazard ratio (HR) 1.34; 95% CI: 1.15–1.56), lung diseases (HR 1.28; 95% CI: 1.10–1.49), and diabetes mellitus (HR 1.46; 95% CI: 1.16–1.84), but not with rheumatic diseases (HR 1.39, 95% CI: 0.92–2.09) or malignant diseases (HR 1.18, 95% CI 0.97–1.42).ConclusionsWe demonstrate a significantly increased burden of morbidity, both before and after the diagnosis of hyperthyroidism.
Highlights
To diabetes mellitus (DM) and osteoporosis, hyperthyroidism is one of the most common endocrine disorders, with a lifetime risk of 2–5% [1]
The interpretation of a potential association between hyperthyroidism and a diagnosis of cardiovascular diseases (CVD) may be complicated by misclassification of hyperthyroidism due to nonthyroidal illness [15] or increased awareness of thyroid disease resulting in selection bias or confounding by indication [16]
The results from the overall association analyses of hyperthyroidism and morbidity are shown in table 3
Summary
To diabetes mellitus (DM) and osteoporosis, hyperthyroidism is one of the most common endocrine disorders, with a lifetime risk of 2–5% [1]. It is no surprise that hyperthyroidism has been associated with an increased risk of cardiovascular diseases (CVD) [10,12,13]. Diagnostic procedures and/or treatment of CVD may increase the risk of developing hyperthyroidism e.g. due to the use of iodine containing substances (i.e. x-ray contrast agents and amiodarone) [14]. The interpretation of a potential association between hyperthyroidism and a diagnosis of CVD may be complicated by misclassification of hyperthyroidism due to nonthyroidal illness [15] or increased awareness of thyroid disease resulting in selection bias or confounding by indication [16]. Genetic confounding could hamper the interpretation of data, since hyperthyroidism [17], CVD [18] as well as stroke [19] demonstrate familial and to some degree individual clustering. We aimed at evaluating various morbidities before and after the diagnosis of hyperthyroidism
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