THYROID AUTOANTIBODIES IN HLA‐GENOTYPED TYPE 1 DIABETIC FAMILIES: SEX‐LIMITED DR5 ASSOCIATION WITH THYROID MICROSOMAL ANTIBODY

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Abstract
SUMMARY: Thyroid autoantibodies are common in Type I diabetics and their first degree relatives and may be part of the autoimmune diathesis present within such families. We have measured the prevalence of microsomal (M‐Ab) and thyroglobulin (Tg‐Ab) autoantibodies in 84 HLA‐typed families having a Type 1 diabetic child, using enzyme‐linked immunosorbent assay techniques. Thyroid autoantibodies were detectable in 201/407 (49%) individuals in these families. Both autoantibodies were significantly more frequent in the subsets of parents, diabetic children and their non‐diabetic siblings than in groups of control adults and children. The prevalence of these autoantibodies in the diabetic families was increased in both sexes with a female:male ratio of 1.4:1. Antigen DR5 was significantly associated with M‐Ab production but only for male subjects (P= 0.005 after correction for the number of DR antigens tested). No significant associations were encountered for Tg‐Ab. Within‐family analyses indicated that thyroid autoantibodies occurred with increased prevalence in HLA‐identical or haplo‐identical siblings of autoantibody‐positive index cases in comparison to control children. We conclude (1) the DR association with thyroid autoantibody production in this diabetes‐selected population was thyroiditis‐related and not diabetes‐related, and (2) the DR5 association was restricted to males and the production of M‐Ab. These data are consistent with the hypothesis that multiple genetic and non‐genetic factors played a role in the high prevalence of thyroid autoantibodies in this population.