How many eventually develop hypothyroidism? A 5-year follow-up of Turner syndrome

We studied the prevalence and incidence of hypothyroidism in 171 women with Turner syndrome (TS) during a period of 5 years. At the mean age of 33 years, 19% were treated for hypothyroidism and another 11% had newly detected disease, i.e. 30% had hypothyroidism, evenly distributed among the karyotypes. Elevated thyroid peroxidase antibody titer (TPO) was present in 30% of all TS and in 37% of those with hypothyroidism. After a 5-year follow-up, another 15% developed hypothyroidism giving an annual incidence of 3%. Altogether, 45% had hypothyroidism at the mean age of 38 years. In TS above 50 years of age 47% had hypothyroidism. In conclusion, almost every second TS woman will most probably develop hypothyroidism and those with elevated TPO levels are at highest risk.