Autoimmune thyroid disease in Chinese children with IDDM

Higher Risk of Thyroid Disorders in Young Patients with Type 1 Diabetes: A 12-Year Nationwide, Population-Based, Retrospective Cohort Study

BACKGROUND

The association between type 1 diabetes and thyroid autoimmunity has been studied in various populations, but seldom on Taiwanese children and adolescents. Therefore, the aim of this study was to examine the incidence of autoimmune thyroid disorders in Taiwanese children and adolescent patients with type 1 diabetes, based on data from a nationwide, population-based, health claims database.

METHODS

Using Taiwan's National Health Insurance Research Database, we identified 3,652 patients with type 1 diabetes between 2000 and 2012. A comparison cohort was assembled, which consisted of five patients without type 1 diabetes, based on frequency matching for sex and 3-year age interval, for each patient with type 1 diabetes. Both groups were followed until diagnosis of thyroid disorders or the end of the follow-up period. Poisson regression models were used to calculate incidence rate ratios for the thyroid disorders between the type 1 diabetes cohort and the comparison cohort.

RESULTS

Simple and unspecified goiter (International Classification of Diseases, 9th Revision, Clinical Modification [ICD-9-CM] code 240), thyrotoxicosis (ICD-9-CM code 242), unspecified hypothyroidism (ICD-9-CM code 244.9), and thyroiditis (ICD-9-CM code 245) showed significantly higher incidences in the type 1 diabetes cohort compared with the control cohort, with incidence rate ratios of 2.74, 6.95, 6.54, 16.07, respectively.

CONCLUSIONS

Findings from this nationwide, population-based cohort study showed that the incidences of autoimmune thyroid disorders were significantly higher in Taiwanese children and adolescents with type 1 diabetes compared with those without the disease.

Genetic epidemiology of type 1 diabetes mellitus in Taiwan

Some environmental and genetic factors play important roles in etiopathogenesis of type 1 or insulin-dependent diabetes mellitus (IDDM). HLA genes, the IDDM1 locus located the human chromosome 6, were found to be associated with insulin-dependent diabetes mellitus. However, the incidence of IDDM varied greatly among various populations. To evaluate the pathogenetic factors contributing to the development of IDDM in Taiwan, HLA typing was performed in a group of IDDM unrelated individuals and IDDM pedigrees along with the normal controls from the northern Taiwan. DNA genotypes of class II HLA were done by polymerase-chain-reaction based oligotyping techniques. We confirmed that class II HLA genes were significantly associated with IDDM in Taiwan. To study detailed molecular structure of class II HLA molecules and disease association, we examined several amino acid residues on DQalpha and DQbeta chains and the molecular mechanisms to explain the heterozygotic effect of the DR3/DR4 and DR3/DR9 in the Chinese population. Linkage analysis in our pedigrees confirmed the association between HLA and IDDM in population association studies. Among the several class II alleles, a closer segregation of HLA-DQB1*0401 to the affected persons might suggest that HLA-DQB1*0401 itself or an allele closely linked to the DQB1 locus was the IDDM-predisposing allele in Taiwanese. For IDDM2 (INS) region, association with IDDM was not found due to that more than 90% of the population carried class I alleles. In our collection of IDDM, we found few cases (2.4%) carried mitochondrial DNA mutation. Our studies in Taiwanese confirm a multigenetic nature for IDDM.

Goitre in southern Chinese children in Hong Kong

In a 9-year retrospective review of goitre in Chinese children in Hong Kong, 84 children and adolescents were identified. There was a female predominance with a male:female ratio of 1:5.5. The majority of patients (95%) were found to have diffuse enlargement of the thyroid gland. Forty-nine were found to have Graves' disease. The mean age of presentation of patients with Graves' disease was 11.34 years. Forty-three of them were found to have thyroid autoantibodies. Only two cases of autoimmune thyroiditis with thyroid autoantibodies were diagnosed. The other causes of goitre include simple colloid goitre, multinodular goitre and suppurative thyroiditis. The spectrum of disease causing goitre in Chinese children is thus quite different from that reported in Caucasian children in developed countries. Further studies are necessary to define the genetic or environmental factors resulting in the observed differences.