The Evolution of Thyroid Function after Presenting with Hashimoto Thyroiditis Is Different between Initially Euthyroid Girls with and Those without Turner Syndrome.

AIM: To prospectively investigate, during a 5-year follow-up, whether the prognosis of thyroid function with Hashimoto thyroiditis (HT) is different in euthyroid girls with Turner syndrome (TS) than in euthyroid girls without TS.
DESIGN: In 66 TS girls and 132 non-TS girls with euthyroid HT and similar thyroid functional test results at HT diagnosis, we followed up the evolution of thyroid status over time.
RESULTS: At the end of follow-up, the TS girls exhibited higher TSH levels, lower fT4 levels, and lower prevalence rates of both euthyroidism and subclinical hypothyroidism, but higher prevalence rates of both overt hypothyroidism and hyperthyroidism, irrespective of the karyotype.
CONCLUSIONS: An association with TS is able to impair the long-term prognosis of thyroid function in girls with HT. Such an effect occurs irrespective of thyroid functional test results at HT diagnosis and is not necessarily linked with a specific karyotype.