Treatment of Thyrotoxicosis
Author: Hristozov К.
Thyrotoxicosis is a collective term including a group of diseases of different etiology, characterized by elevated levels of circulating thyroid hormones. Hyperthyroidism refers specifically to increased synthesis and secretion of thyroid hormones due to Graves’ disease (GD), toxic adenoma, and pituitary adenoma producing thyroid-stimulating hormone (TSH). The state of thyrotoxicosis without hyperthyroidism includes the various forms of thyroiditis, struma ovarii, iodine-induced and exogenous thyrotoxicosis. Grave’s disease is an autoimmune disease that is triggered by circulating autoantibodies directed against TSH receptors on the surface of thyrocytes. It represents the most common cause of hyperthyroidism, with a chronic-progressive course, prone to exacerbation or relapses after treatment. Extrathyroidal manifestations of the disease include thyroid-associated ophthalmopathy (TAO), pretibial myxedema, thyroid acropachia, and others, which are not found in other forms of thyrotoxicosis. Diagnosis is based on clinical presentation, hormonal and immunological findings, and imaging studies. Current therapy includes medical treatment with thyrostatics (thionamides) and definitive treatment – surgical or radioiodine therapy. Alongside, beta-blockers are recommended, as well as sedative drugs, antioxidants, in severe forms of thyrotoxicosis – corticosteroids are administered and in rhythm disorders – anticoagulants. The goal is to restore and maintain an euthyroid state and permanent immunological remission. The more common side effects of thyrostatic therapy are expressed in the suppression of granulopoiesis in the bone marrow, allergic reactions, myopathy, gastrointestinal – characterized mainly by methyl-mercaptoimidazole (MMI), and hepatotoxic action of propylthiouracil (PTU). Current recommendations for the treatment of TAO are based on an individualized approach, and transitory deterioration has been observed as a disadvantage of radioiodine therapy, as one of the three therapeutic options for the treatment of GD, which can be avoided with a protective corticosteroid course. Treatment options in children are the same as in adults, but the risks and benefits of each method are different. New European Thyroid Association recommendations from 2022 year for the treatment of childhood GD include a prolonged course of MМI as first-line treatment, with a preference for dose titration over the combination method of therapy with levothyroxine, and refraining from the use of PTU. As definitive treatment, total thyroidectomy or radioiodine therapy is recommended with the goal of complete thyroid ablation with subsequent replacement therapy. During pregnancy, treatment with MMI is contraindicated. If necessary, the same should be performed after the age of 16 week of gestation and only in case of proven side effects of the ongoing PTU therapy. The optimal time for surgical intervention is the second trimester. In elderly people it is preferred prolonged thyrostatic or radioiodine therapy. A challenge in daily practice is the recognition of the two types of drug-induced thyrotoxicosis due to Amiodarone intake. Their diagnosis is essential because the two forms are based on different therapeutic approach.