Objective: To determine the prevalence of autoimmune thyroid disease in Familial Alzheimer's Disease kindreds and to ascertain whether there is any evidence for genetic linkage between the two conditions.
Design: Retrospective study of Familial Alzheimer's Disease kindreds.
Patients: Seventy affected and unaffected family members from 12 kindreds.
Measurements: Anti-thyroglobulin and anti-microsomal autoantibody status was determined using an enzyme-linked immunosorbent assay. Thyrotrophin levels were determined by an immunoradiometric assay.
Results: Of the family members, 41.4% had evidence of autoimmune thyroid disease, with significant co-segregation between the presence of thyroid autoantibodies and the development of Alzheimer's disease (P less than 0.01).
Conclusions: This study demonstrates a very high prevalence of autoimmune thyroid disease in Familial Alzheimer's Disease kindreds and suggests that a genetic factor contributing towards the development of autoimmune thyroid disease may be located on chromosome 21 within close proximity to the Familial Alzheimer's Disease gene.