In Young Patients with Turner or Down Syndrome, Graves' Disease Presentation Is Often Preceded by Hashimoto's Thyroiditis

Background: It is known that, in the general population, there exists a continuum between Hashimoto's thyroiditis (HT) and Graves' disease (GD) within the spectrum of autoimmune thyroid diseases, although the mechanisms involved in the metamorphosis from HT to GD or vice versa have not been elucidated as of yet. The aim of this study was to ascertain whether the association with Down or Turner syndromes (DS and TS) may affect the switching process from HT to GD. Methods: Thirty-five young GD patients with either DS or TS (group A) and 109 age-matched GD patients with neither DS nor TS were retrospectively investigated in order to either confirm or exclude antecedents of HT. The investigations were based on either clinical records or questionnaires addressed to family pediatricians. Retrospective investigations also aimed to ascertain how many patients in each group exhibited a biochemical picture of either subclinical or overt hypothyroidism at the time of HT diagnosis, and how many had received levothyroxine (L-T4) therapy prior to the onset of GD. In both groups, all the patients with documented antecedents of HT underwent an assessment of their iodine status after GD diagnosis. Results: Antecedents of HT were significantly more common in group A than in group B (25.7% vs. 3.7%, p=0.0004), with a time interval between HT and GD that was significantly higher in group A (p=0.003). Both thyroid function and autoimmunity tests at HT presentation and the prevalence of patients who underwent L-T4 therapy prior to GD diagnosis were not significantly different in the two groups, nor was the iodine status after GD diagnosis. Conclusions: In young patients with TS or DS, GD presentation is often (25.7% of cases) preceded by HT. This evolution trend does not seem to be conditioned by either thyroid tests at HT diagnosis, or L-T4 treatment, or iodine status alterations. Patients with these chromosomopathies and coexisting HT may be at high risk of progressing to GD. The pathophysiological bases of these findings need to be clarified.