Autoimmune thyroid disease and thyroid autoantibodies in rheumatoid arthritis patients and their families.

All 504 available members from 58 multicase rheumatoid arthritis (RA) families were interviewed and examined for the presence or history of autoimmune thyroid disease and were tested serologically for thyroid autoantibodies. The serological data were compared with those from a major population survey which used the same assay methods. Overall, 6% had thyroid disease with a fivefold female excess. Thyroglobulin antibodies were present in 5% of males and 11% of females and thyroid microsomal antibodies in 5% of males and 15% of females. These rates were all significantly greater than published rates for the general population. The differences persisted after analysing separately by age group. The results confirm the suggestions by others that there may be a common genetic link between RA and autoimmune thyroid disease.