Familial Distribution of Thyroid Disease and Diabetes: Further Evidence for Aetiological Heterogeneity of Diabetes Mellitus

The prevalences of thyroid disease, insulin-dependent and non-insulin-dependentdiabetes were compared in first degree relatives of diabeticswith and without coexisting autoimmune thyroid disease. Thyroiddisease was more common in siblings of diabetics with thyroiddisease than in those of diabetics without thyroid disease.Insulin-dependent diabetes was more common in siblings of diabeticswith a personal or family history of thyroid disease than inthose of diabetics without such a history. The prevalence ofnon-insulin-dependent diabetes was unrelated to that of thyroiddisease but was greater In siblings of non-insulin-dependentdiabetics than in those of insulin-dependent diabetics. Thesefindings add further support to the aetiological distinctionbetween insulin-dependent and non-insulin-dependent diabetesand suggest that further heterogeneity exists within the populationof insulin-dependent diabetics based on the presence of a personalor family history of thyroid disease.