Celiac disease is often associated with autoimmune diseases, such as dermatitis herpetiformis, autoimmune gastritis, type I diabetes, psoriasis and certain autoimmune thyroid diseases, such as Hashimoto's thyroiditis and Basedow's disease.
Although it is certain that people with celiac disease are more prone to suffer from thyroid disease, it is difficult to provide accurate percentages, given the discord among the various epidemiological data that prevent the establishment of the exact relationships between the two diseases.
In general, it is estimated that a patient suffering from celiac disease is three times more likely to suffer from diseases affecting the thyroid. However, the cases of hypo and subclinical hyper-thyroidism related to autoimmune thyroid diseases that escape some studies due to serological findings within the normal range should be considered. Although the values of TSH and thyroxine (T4) fall within the norm in these celiac patients, it is often possible to highlight a positive dosage of antitireoglobulin and anti-thyroxine antibodies, which testify to an increased risk of developing associated hypo- or hyper thyroid disorders at autoimmune thyroid diseases. It should also be emphasized that the association between celiac disease and autoimmune thyroid disease is not a consequence; this means that autoimmune thyroid diseases can be diagnosed both before and at a later date than the detection of celiac disease.
Considering the link, albeit weak, between the two diseases, the opposite discourse is also valid, namely the increased risk of celiac disease in patients suffering from autoimmune thyroiditis compared to the general population. Therefore, in these subjects there will be a greater percentage of positivity to the Ab-anti-tTG (anti-transglutaminase antibodies) and EMA (antiendomysium antibodies) test.
Some studies have observed that the prevalence of autoimmune thyroid disease in the celiac population is proportional to the duration of exposure to gluten; in other words, the diagnosis is much later and the greater the risk that celiac disease is associated with autoimmune thyroid disorders. For the same reason, a gluten-free diet seems to be able to positively influence the course of these thyroid diseases, but there are also exceptions highlighted by numerous studies that express a contrary opinion; therefore, it is not yet clear if and how much autoimmune thyroiditis in celiac patients depends on the duration and intensity of exposure to gluten, and vice versa. In the case of hypothyroidism associated with celiac disease, for example, we have seen that in many cases a gluten-free diet can reduce the dosage of replacement therapy with l-thyroxine; this effect could however be mostly due to the better intestinal absorption of the drug, deriving from the restoration of the normal structure and functionality of the enteric mucosa.
As explained in the article it is desirable a careful follow up of patients suffering from celiac disease, which includes the periodic dosage of thyroid hormones and TSH to investigate thyroid function. Such investigations are particularly important for celiacs in whom the presence of antithyroid autoantibodies has already been found.
