Graves' disease: Epidemiology, genetic and environmental risk factors and viruses.

Graves' disease (GD) is the most common cause of hyperthyroidism in developed Countries. It is more common between 30 and 60 years; 5-10 times more frequent in women. The genetic predisposition accounts for 79% of the risk for GD, while environmental factors for 21%. About 70% of genes associated with autoimmune thyroid disorders (AITD) are implicated in T-cell function. Among GD endogenous factors, estrogens, X-inactivation and microchimerism are important. Among environmental risk factors, smoking, iodine excess, selenium and vitamin D deficiency, and the occupational exposure to Agent Orange have been associated with GD. Many studies showed that HCV is associated with thyroid autoimmunity and hypothyroidism, in patients with chronic HCV hepatitis (CHC); a significant link has been shown also between HCV-related mixed cryoglobulinemia and risk for GD. Moreover, IFN-α-treated CHC patients develop GD more frequently. Novel studies are needed about possible risk factors to reduce the occurence of GD in West Countries.

Graves' disease: Clinical manifestations, immune pathogenesis (cytokines and chemokines) and therapy.

Graves' disease (GD) is characterized by thyrotoxicosis, caused by the presence of circulating thyroid stimulating antibodies (TSAb), that are determinant also in the pathogenesis of its extrathyroidal manifestations [Graves' ophthalmopathy (GO), pretibial myxedema]. T helper (Th)1 immune response prevails in the immune-pathogenesis of GD and GO, during the active phase, when Th1 chemokines, and their (C-X-C)R3 receptor, play a key role. In GD, the existing treatments are not ideal for hyperthyroidism (long-term remission with anti-thyroid-drugs only in 50% of patients; while radioiodine and surgery cause hypothyroidism). In GD, antigen-specific therapy has been recently published, with the induction of T cell tolerance via an immunization by TSH-R peptides. In GO, rituximab and drugs targeting cytokines have been evaluated. Furthermore, teprotumumab (a human monoclonal anti-IGF-1R blocking antibody) showed to be very effective in GO patients. Further researches are necessary to identify novel effective therapies targeting GD, or GO.

Novel therapies for thyroid autoimmune diseases: An update.

A Th1 immune-preponderance has been shown in the immunopathogenesis of autoimmune thyroiditis (AT), Graves' disease (GD) and Graves' Ophthalmopathy (GO), in which the Th1-chemokines (CXCL9, CXCL10, CXCL11), and their (C-X-C)R3 receptor, have a crucial role. Methimazole, and corticosteroids have been shown to modulate these chemokines; several efforts have been done to modulate the autoimmune reaction with other drugs, i.e. PPAR-γ, or -α ligands, or antibodies, or small molecules directed against CXCL10, or CXCR3. Antigen-specific therapy for GD, by inducing T cell tolerance through an immunization with TSH-R peptides, has been published. Drugs targeting cytokines [anti-TNFα (Etanercept), and anti-IL-6 (Tocilizumab)], and RTX (a chimeric monoclonal antibody vs. CD20) have been used in GO, with promising results. Teprotumumab (a human monoclonal anti-IGF-1R blocking antibody) has been investigated in a trial, showing it was very effective in GO patients. Still, more studies are needed for new therapies targeting autoimmune thyroid disorders.

Hashimotos' thyroiditis: Epidemiology, pathogenesis, clinic and therapy.

Hashimoto's thyroiditis (HT), the most frequent autoimmune thyroid disorders (AITDs), is the leading cause of hypothyroidism in the iodine-sufficient areas of the world. About 20-30% of patients suffers from HT, whose cause is thought to be a combination of genetic susceptibility and environmental factors that causes the loss of immunological tolerance, with a consequent autoimmune attack to the thyroid tissue and appearance of the disease. The pathologic features of lymphocytic infiltration, especially of T cells, and follicular destruction are the histological hallmark of autoimmune thyroiditis (AIT), that lead to gradual atrophy and fibrosis. An important role in the immune-pathogenesis of AITDs is due to chemokines and cytokines. In about 20% of patients, AITDs are associated with other organ specific/systemic autoimmune disorders. Many studies have demonstrated the relationship between papillary thyroid cancer and AITD. The treatment of hypothyroidism, as result of AIT, consists in daily assumption of synthetic levothyroxine.

The aggregation between AITD with rheumatologic, or dermatologic, autoimmune diseases.

Autoimmune thyroid diseases (AITD) are organ-specific autoimmune disorders mediated by Th1 lymphocytes, whose main clinical presentations are Hashimoto's thyroiditis (HT), or Graves' disease (GD). HT, GD, thyroid autoantibodies and thyroid dysfunctions have been shown in systemic rheumatologic diseases (as Sjögren's syndrome, systemic lupus erythematosus, rheumatoid arthritis, systemic sclerosis, or cryoglobulinemia). New associations of AITD with other autoimmune diseases are being discovered, for example with psoriatic arthritis and dermatological diseases. Several investigations suggest the importance of a shared genetic susceptibility and of environmental factors in patients with AITD and associated systemic autoimmunity. A major Th1 autoimmune response occurs in the initial, and/or active phases of organ-specific autoimmune disorders and/or systemic rheumatologic diseases with increased serum, or tissue, expressions of the Th1 chemokine CXCL10. Thyroid dysfunctions might have an important clinical impact, so a periodic thyroid screening in women with systemic or dermatological autoimmunity, overall in presence of thyroid autoantibodies is suggested.