Endocrine Abstracts

JOINT271

Background and Aims: Graves’ disease (GD) and Hashimoto’s thyroiditis are autoimmune disorders that can transition from one to the other. The shift from hypothyroidism to GD is rare. This study compared clinical characteristics, treatments, and outcomes in patients with new-onset GD following hypothyroidism vs those with new-onset GD without prior thyroid disease.

Methods: This retrospective cohort study used the electronic medical database of Maccabi Healthcare Services, an Israeli health maintenance organization. We included adults with new-onset GD between 1.2010–12.2022 who had thyroid-stimulating immunoglobulin (TSI) titers >140% within a year of thyrotoxicosis diagnosis. Subjects with prior amiodarone use were excluded. Data included demographics, clinical history, treatments, and laboratory Results The end of follow-up was 31.10.2024. Data were analyzed using chi-square or Fisher’s exact tests for categorical variables, t-tests or Mann-Whitney U tests for continuous variables, and Cox regression models adjusted for age and sex.

Results: We included 2402 patients with new-onset GD. Of these, 2146 had no prior thyroid disease (GD-controls) and 256 had prior hypothyroidism (post-hypo-GD patients). Compared to GD-controls, post-hypo-GD patients were older (51.4±14.3 vs. 47.4±13.6 years; P < 0.001), predominantly female (88.1% vs. 76.9%; P < 0.001), and had a higher prevalence of autoimmune disease (19.5% vs. 12.9%; P = 0.003). At diagnosis, post-hypo-GD patients had lower median free thyroxine (fT4) levels (21.7 [interquartile range (IQR), 17.5-28.5] vs. 26.8 [IQR,19.8-38.6] pmol/l; P < 0.001) and free triiodothyronine (fT3) levels (8.5 [IQR,5.9-11.5] vs. 10.4 [IQR,7.2-15.8] pmol/l; P < 0.001). Over a median follow-up of 7.2 [IQR,4.6–10.9] years, antithyroid medications were used less frequently in post-hypo-GD patients (65.6% vs. 81.0%; hazard ratio [HR] 0.64; P < 0.001). Radioactive iodine ablation (HR 0.68; P = 0.26) and total thyroidectomy (HR 1.29; P = 0.33) were utilized at comparable rates. Post-hypo-GD patients had a higher incidence of hypothyroidism requiring levothyroxine (41.8% vs. 21.0%; HR 2.58; P < 0.001).

Conclusions: Patients with post-hypo-GD present with milder thyrotoxicosis and more often revert to hypothyroidism.