While the capsule is intact and the gland itself is still distinct from surrounding tissue, microscopic examination can provide a more revealing indication of the level of damage.Histologically, the hypersensitivity is seen as diffuse parenchymal infiltration by lymphocytes, particularly plasma B-cells, which can often be seen as secondary lymphoid follicles (germinal centers, not to be confused with the normally present colloid-filled follicles that constitute the thyroid). Atrophy of the colloid bodies is lined by Hürthle cells, cells with intensely eosinophilic, granular cytoplasm, a metaplasia from the normal cuboidal cells that constitute the lining of the thyroid follicles. Severe thyroid atrophy presents often with denser fibrotic bands of collagen that remains within the confines of the thyroid capsule. Diagnosis
Diagnosis is usually made by detecting elevated levels of antithyroid peroxidase antibodies in the serum, but seronegative (without circulating autoantibodies) thyroiditis is also possible.Given the relatively nonspecific symptoms of initial hypothyroidism, Hashimotos thyroiditis is often misdiagnosed as depression, cyclothymia, premenstrual syndrome, chronic fatigue syndrome, fibromyalgia, and less frequently, as erectile dysfunction or an anxiety disorder. On gross examination, a hard goiter that is not painful to the touch often presents; other symptoms seen with hypothyroidism, such as periorbital myxedema, depend on the current state of progression of the response, especially given the usually gradual development of clinically relevant hypothyroidism. Testing for thyroid-stimulating hormone (TSH), free T3, free T4, and the antithyroglobulin antibodies (anti-Tg), antithyroid peroxidase antibodies (anti-TPO, or TPOAb) and antimicrosomal antibodies can help obtain an accurate diagnosis.
Iodine also promotes follicular cell apoptosis and has an influence on immune cells (augmented maturation of dendritic cells, increased number of T cells, stimulated B-cell immunoglobulin production).Data from The Danish Investigation of Iodine Intake and Thyroid Disease shows that within two cohorts (males, females) with moderate and mild iodine deficiency, the levels of both thyroid peroxidase and thyroglobulin antibodies are higher in females, and prevalence rates of both antibodies increase with age. Sex
Study of healthy Danish twins divided to three groups (monozygotic and dizygotic same sex, and opposite sex twin pairs) estimated that genetic contribution to thyroid peroxidase antibodies susceptibility was 61% in males and 72% in females, and contribution to thyroglobulin antibodies susceptibility was 39% in males and 75% in females.The high female predominance in thyroid autoimmunity may be associated with the X chromosome. It contains sex and immune-related genes responsible for immune tolerance. A higher incidence of thyroid autoimmunity was reported in patients with a higher rate of X chromosome monosomy in peripheral white blood cells.Another potential mechanism might be skewed X-chromosome inactivation, leading to the escape of X-linked self-antigens from presentation in the thymus and loss of T-cell tolerance.Having other autoimmune diseases is a risk factor for developing Hashimotos thyroiditis, and the opposite is also true.