Excess thyroid hormone causes a widespread disturbance in metabolism, since thyroid hormone effectively regulates the metabolic level in the body. For practical purposes, the two names, thyrotoxicosis, or hyperthyroidism, are used interchangeably. Hashimoto's thyroiditis is typically characterized by thyroid enlargement and often underactivity. Idiopathic hypothyroidism is usually the result of Hashimoto's thyroiditis, and myxedema is the most advanced form of this illness. Of course hypothyroidism and myxedema can also be induced by other causes of thyroid hormone deficiency.
Patients can move from one or the other category, depending upon the stage of their illness.
At a later stage, this individual might become hyperthyroid and fit in the category of Graves' disease. Or, the patient might have progressive destruction of the thyroid, or develope blocking antibodies, and become hypothyroid or ultimately develop myxedema. The common features of the autoimmune thyroid diseases include the immune reactivity to specific thyroid antigens. Patients with AITD may have antibodies, less frequently, to adrenal steroidogenic enzymes, ovarian steroidogenic enzymes, and components of the pituitary gland, thus qualifying for the Multiple Endocrine Autoimmune Syndrome 6 . Anti-cardiolipin antibodies are present in increased incidence in patients with autoimmune thyroid disease, including Graves disease.