Thyroid dysfunction in patients with diabetic retinopathy

Thyroid disease and diabetes mellitus (DM) are the most common endocrinopathies in clinical practice that interact with each other. On the one hand, thyroid hormones regulate carbohydrate metabolism and pancreas functions, and on the other hand DM affects the function and work of the thyroid gland. Diabetic retinopathy (DR) is a highly specific neurovascular complication of both type 1 and type 2 DM, which is a significant cause of vision loss on a global scale. In DM, the internal blood-retinal barrier is the earliest to be damaged, and changes in neuroretina result from the loss of its adaptation to metabolic disorders. Patients with DM have a higher incidence of thyroid disease compared to people without DM. The coexistence of DM with thyroid disease leads to endothelial damage, and the degree of its dysfunction has a significant impact on the course of macro- and microangiopathic complications in patients. There are few reports in the literature about the impact of thyroid disease and substitution of levothyroxine preparations on the development and course of DR in patients with DM. It is unknown whether the fact that patients with unrecognised hypothyroidism are not treated with levothyroxine preparations disrupts thyroid hormone homeostasis to the extent that it may contribute to a higher incidence of DR. This review discusses recent clinical trials for thyroid dysfunction in patients with DR.