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 d eveloping autoimmune thyroid disease. Studies assessing the influence of ka ryotype on thyroid autoimmunity in adults with TS have yielded conflicting results but have been limited by small numbers. The aim of this study was t o determine the frequency of thyroid autoimmunity in a large cohort of wome n with TS and to assess the Influence of karyotype on the development of th yroid 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 (rang e 16-52 years). Information regarding the presence of thyroid disease, kary otype, 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 autoantibo dies and 16% of women were hypothyroid on replacement therapy with thyroxin e. However, 83% of women with an X-Isochromosome had positive thyroid autoa ntibodies compared with 33% of women with other karyotypes (P < 0.0001). Wo men with an isochromosome-X karyotype were also significantly more likely t o become frankly hypothyroid and require thyroxine compared with other kary otypes (37.5% isochromosome-X vs. 14% 45, X vs. 6% other karyotypes P = 0.0 034). CONCLUSIONS In this large cohort of women with TS we have shown that the ri sk of developing autoimmune thyroid disease is particularly high in women w ith an X-isochromosome, suggesting that a gene on the long arm of the X chr omosome (Xq) may play an important pathogenetic role in the development of autoimmune thyroid disease.