Part of “CHAPTER 45 – HYPOTHYROIDISM“

Hypothyroidism may develop from any one of a number of acquired thyroid diseases or their treatments, from hereditary abnormalities, or secondarily from hypothalamic-pituitary disease (Table 45-1). Usually, hypothyroidism develops as a consequence of Hashimoto disease or of prior radioactive iodine or surgical management of Graves disease. In 20% of patients treated for Graves disease, the hypothyroidism that develops after radioactive iodine therapy occurs within the first 12 months of treatment. The initial incidence is locally influenced by the dosage of radiation used. A slower but relentlessly progressive increase in incidence of hypothyroidism continues at a rate of 2% to 4% of the population at risk each year.7

Hypothyroidism may also develop as a late consequence of Graves disease in patients who previously were not treated with radioactive iodine or surgery.8 Studies suggest that thyrotropin-binding inhibitor immunoglobulins circulate in some of these patients.9 The hyperthyroidism of Graves disease may be supplanted by hypothyroidism, because the autoimmune production of thyrotropin receptor-blocking antibodies has resulted in inhibition of thyroid-stimulating hormone (TSH) receptor function.