The principal drawback to radioactive iodine therapy is the high rate of postablative hypothyroidism, which occurs in at least 50% of patients immediately after therapy, with additional cases developing at a rate of 2% to 3% per year. Based on the assumption that hypothyroidism will develop, these patients should be given lifetime thyroid replacement therapy. Beta-adrenergic blocking agents such as propranolol or atenolol are useful adjunctive therapy for control of sympathomimetic symptoms such as tachycardia (51). An additional benefit of beta-blockers is the blocking of peripheral conversion of T4 to T3. In rare cases of thyroid storm, PTU, beta-blockers, glucocorticoids, and high-dose iodine preparations (intravenous sodium iodide) should be administered immediately, and referral to an intensive care unit is advisable.
Thyroid Nodules and Thyroid nodules are common and found on physical examination in up to 5% of patients. Cancer Nodules may be demonstrated on ultrasound in approximately 50% of 60-year-olds. The vast majority of nodules when discovered are asymptomatic and benign; however, malignancy and hyperthyroidism must be excluded (52). Ultrasound-guided fine-needle aspiration is recommended in the presence of the following factors: history of radiation to the head, neck, or upper chest; family history of thyroid cancer; ultrasound findings suggestive of malignancy; or a nodule larger than 1.5 cm in diameter (53).
Thyroid function tests should be performed before fine-needle aspiration and, if results are abnormal, the underlying disease should be treated. Because most nodules are “cold” on scanning, it is more cost-effective to proceed with tissue sampling rather than scanning. Needle biopsy provides a diagnosis in 95% of cases; in the 5% of patients in whom the diagnosis cannot be established, excisional biopsy is necessary. Only 20% of excisional biopsies of an “indeterminate aspiration” are found to be malignant (54). Lesions that are confirmed malignant on biopsy should be treated with extirpative surgery, and benign nodules should be palpated every 6 to 12 months. Thyroxine suppressive therapy for benign nodules is not recommended (53).
Papillary thyroid carcinoma is the most common malignancy, found in 75% of thyroid cancers. For unclear reasons the incidence of papillary cancer increased by almost threefold in the past 30 years, from 2.7 to 7.7 per 100,000 people (55). This may represent the more ready diagnosis of smaller cancers. The majority of cancers are found incidentally during routine examinations. Risk factors include a history of radiation exposure during childhood and family history. Signs include rapid growth of neck mass, new onset hoarseness, or vocal cord paralysis. In the setting of rapid growth, fixed nodule, new onset hoarseness, or the presence of lymphadenopathy, it is important to be sure a fine-needle aspiration is done. Thyroidectomy is the primary treatment with radioactive iodine and TSH suppression with thyroxine. Patients younger than 50 years of age with a primary tumor of less than 4 cm at presentation, even with associated cervical lymph node metastasis, are usually cured. In the elderly, anaplastic tumors have a poor prognosis and progress rapidly despite therapy.
Follicular thyroid cancer is the second most common thyroid cancer, comprising up to 10% of cases. These tend to occur in an older population with peak ages of 40 to 60. It has a threefold greater prevalence in women than men. This form of cancer tends to have vascular invasion, frequently with distant metastases. The prognosis tends to be less favorable with this form of cancer than with papillary cancers, although women do have a better prognosis than men.