Autoimmune thyroid syndrome in women with Turner's syndrome--the association with karyotype.

OBJECTIVE: Females with Turner's syndrome (TS) are at an increased risk of developing autoimmune thyroid disease. Studies assessing the influence of karyotype on thyroid autoimmunity in adults with TS have yielded conflicting results but have been limited by small numbers. The aim of this study was to determine the frequency of thyroid autoimmunity in a large cohort of women with TS and to assess the influence of karyotype on the development of thyroid disease. DESIGN, PATIENTS AND MEASUREMENTS: Data were available for 145 women with TS attending a dedicated adult Turner clinic. The mean age was 26 years (range 16-52 years). Information regarding the presence of thyroid disease, karyotype, thyroid autoantibodies and thyroid function was recorded in all. The chi-squared test with Yates' correction was used to assess the association between karyotype and thyroid autoimmunity.
RESULTS: Forty-one per cent of women with TS had positive thyroid autoantibodies and 16% of women were hypothyroid on replacement therapy with thyroxine. However, 83% of women with an X-isochromosome had positive thyroid autoantibodies compared with 33% of women with other karyotypes (P < 0.0001). Women with an isochromosome-X karyotype were also significantly more likely to become frankly hypothyroid and require thyroxine compared with other karyotypes (37.5% isochromosome-X vs. 14% 45, X vs. 6% other karyotypes P = 0.0034).
CONCLUSIONS: In this large cohort of women with TS we have shown that the risk of developing autoimmune thyroid disease is particularly high in women with an X-isochromosome, suggesting that a gene on the long arm of the X chromosome (Xq) may play an important pathogenetic role in the development of autoimmune thyroid disease.