Patients who have Graves disease in association with other autoimmune disorders have a higher rate of transition between thyroid functional states compared with those who have isolated Graves disease, according to study results published in the Journal of Endocrinological Investigation.

The results indicated that despite this difference, Graves disease has similar anthropometric, clinical, and biochemical features at diagnosis when it is isolated vs when it occurs in association with other disorders of the immune system.

The study included patients in Italy with isolated Graves disease (n=136) or Graves disease and another autoimmune disorder (including atrophic gastritis, vitiligo, type 1 diabetes, celiac disease, and Addison disease, among other disorders; n=68). The researchers collected data on clinical history and thyroid workup at disease diagnosis, including serum levels of thyroid-stimulating hormone (TSH), free thyroxine, free triiodothyronine, thyroglobulin antibodies (TgAb), thyroid-peroxidase antibodies (TPOAb), and TSH-receptor antibodies (TRAb). Presence of Graves orbitopathy was also assessed and all participants underwent thyroid ultrasound examination.

At initial diagnosis, patients with Graves disease alone or in association with other autoimmune diseases had no significant differences in female-to-male ratio; age at presentation; thyroid function parameters; serum levels of TRAb, TgAb, and TPOAb; presence of Graves orbitopathy; or thyroid volume.

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However, patients with Graves disease in association with other autoimmune diseases had a 4-fold higher rate of transition from initial hypothyroidism to hyperthyroidism compared with patients who had isolated Graves disease (χ2=6.375; P =.012).

After investigating this observation, the researchers found that for patients with Graves disease and no other autoimmune disorders, serum levels of TRAb had a strong correlation with circulating concentrations of both free triiodothyronine (P <.0001) and free thyroxine (P <.001). However, these correlations were not observed in patients with Graves disease and other autoimmune diseases (P =.058 and P =.435, respectively).

The investigators speculated that a possible explanation for the greater rate of conversion from hypothyroidism to hyperthyroidism in patients with Graves disease and other autoimmune disorders may be a shift in functional activity in TRAbs, from blocking to stimulating antibodies.

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Reference

Rotondi M, Virili C, Pinto S, et al. The clinical phenotype of Graves’ disease occurring as an isolated condition or in association with other autoimmune diseases [published online August 12, 2019]. J Endocrinol Invest. doi:10.1007/s40618-019-01094-7