Yes. Having one autoimmune disease slightly increases your risk of developing one or more additional autoimmune condition. 

Someone with an autoimmune thyroid disorder is more likely to develop another autoimmune condition, such as Addison’s disease, pernicious anaemia or coeliac disease. This risk is still very small, however. For example, between 1.5% to 3.8% of people with autoimmune thyroid disease also have coeliac disease compared to 1% in the general population. [1]  It is thought that about 10 per cent of people with autoimmune hypothyroidism (Hashimoto’s thyroiditis) also have pernicious anaemia.

Although the risk is small, it is important that such conditions are considered in patients with autoimmune thyroid disease if they develop new or nonspecific symptoms. For example, the NICE guidance on coeliac disease recommends that anyone with an autoimmune thyroid condition is also offered testing for coeliac disease at the time of diagnosis.[2]

It is also important for people with Addison’s disease, type 1 diabetes and other autoimmune diseases to be tested regularly for autoimmune thyroid disease.