Hypothyroidism is a condition that results from thyroid hormone deficiency that can range from an asymptomatic condition to a life-threatening disease. The prevalence of hypothyroidism varies according to the population, from up to 3 to 4% in some populations and in the case of subclinical hypothyroidism up to 5–10%. Clinical symptoms of hypothyroidism are diverse, broad, and non-specific and can be related to many systems, reflecting the systemic effects of thyroid hormones. The severity of the symptoms is usually related to the severity of the thyroid hormone deficit. The most common form of hypothyroidism, primary hypothyroidism, is diagnosed when there is elevation of TSH and decrease in the level of free T4 and Subclinical hypothyroidism is diagnosed when there is an elevation of TSH with normal levels of free T4. The most frequent cause of primary hypothyroidism in populations without iodine deficiency is Hashimoto’s thyroiditis or chronic lymphocytic thyroiditis. Iodine deficiency is the main cause of hypothyroidism in populations with deficiency of iodine intake. The treatment of choice for hypothyroidism is thyroxine (T4), which has shown efficacy in multiple studies to restore the euthyroid state and improve the symptoms of hypothyroidism. In subclinical hypothyroidism, the treatment depends on the age, functionality, and comorbidities of the patients. The total replacement dose of levothyroxine in adults is approximately 1.6 mcg/kg; however in elderly patients with heart disease or coronary heart disease, the starting dose should be from 0.3 to 0.4 mcg/kg/day with progressive increase of 10% of the dose monthly.
Part of the book: Cellular Metabolism and Related Disorders
Graves disease is an autoimmune disease, with a genetic susceptibility, activated by environmental factors like stress, iodine excess, infections, pregnancy and smoking. It is caused by thyroid stimulating immunoglobulin (TSI) or thyroid stimulating antibody (TSAb) and is the most common cause of hyperthyroidism with an incidence of 21 per 100,000 per year. Treatment of Graves disease includes antithyroid drugs such as methimazole and propylthiouracil, radioactive iodine therapy and thyroidectomy. Methimazole, an antithyroid drug that belongs to the thioamides class, is usually the first line of treatment due to lower risk of hepatotoxicity compared to propylthiouracil. Radioactive iodine therapy is reserved for those patients who do not respond to antithyroid drugs or have contraindication or adverse effects generated by antithyroid drugs, and thyroid surgery is an option in people with thyroid nodular disease with suspected malignancy or large goiters such as predictors of poor response to antithyroid drugs and radioactive iodine therapy. Multiple factors influence the management of patients with Graves disease including patient and physician preferences, access to medical services and patients features such as age, complications and comorbidities.
Part of the book: Graves' Disease