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Antithyroid drugs are not indicated for definitive treatment because of
universal relapse, and are used only for preparation to ablative therapy
with radioiodine or surgery. The indications to specific forms of treatment
in toxic adenoma and toxic multinodular goiter are summarized in Tables
5 and 6.
Table 5: Factors favoring specific forms of treatment in toxic and pretoxic adenoma. Surgery
Table 6: Factors favoring specific forms of treatment in toxic multinodular goiter. Surgery
Toxic Adenoma Hyperthyroidism due to toxic adenoma responds well to radioiodine, and the nodule is partially reduced by this form of therapy[2, 3]. In severe hyperthyroidism, pretreatment with thionamides is indicated, but radioiodine should be given before restoration of extranodular thyroid function by TSH. Under these conditions, post-radioiodine hypothyroidism is rare. Relatively high doses of 131I are used, generally 200 µCi/g of estimated nodule weight. Surgery is a more appropriate choice in large (>5 cm) nodules with associated pressure symptoms. Young age also favors surgery with respect to radioiodine. Lobectomy is indicated in classic toxic adenoma in otherwise normal thyroid glands. When single hyperfunctioning thyroid nodules occur in a multinodular goiter subtotal or near total thyroidectomy is indicated. Hypothyroidism does not occur in patients submitted to lobectomy, but may well occur in those treated with subtotal thyroidectomy. Substitution treatment with L-T4 is mandatory in all cases of hypothyroidism. Autonomously functioning thyroid nodules (pretoxic adenomas) are rather frequent, mainly in endemic areas. These nodules may remain unchanged in volume and function for years or decades, but their evolution to thyrotoxicosis may be insidious, and is frequently recognized after the appearance of cardiac complications. Because of this, we believe that autonomously functioning thyroid nodules deserve radioiodine or surgical treatment. Most recently percutaneous ethanol injection treatment (PEIT) has been offered as an additional option for both toxic and pretoxic adenoma. PEIT consists in the administration of 98 % ethanol (total amount 1.5 ml per gram of nodular tissue) by a needle inserted into the nodule. Though generally well tolerated, a transient burning sensation is experienced by most patients. More serious side effects are rare, and include transient dysphonia, general malaise, and transient exacerbation of thyrotoxicosis in untreated toxic adenoma. Normalization of thyroid function tests and reduction of the nodular volume have been reported in more than 70 % of patients after 3 to 5 injections. The response to PEIT in large nodules is less satisfactory. PEIT can be proposed as alternative treatment to patients with small toxic adenomas or, more appropriately, with pretoxic nodules. Since the extranodular tissue is unaffected by the treatment, there is no risk of hypothyroidism which, instead, is a relatively common complication of radioiodine administration in patients with pretoxic nodules. The need for repeated injections (up to 8), the relatively high cost, and the possible discomfort associated with intranodular ethanol injection may however limit the use of this form of treatment. Toxic Multinodular Goiter Toxic multinodular goiter is more frequent in patients older than age 50, who may have other, nonthyroidal illnesses adding a risk to surgery. Therefore, many patients with toxic multinodular goiters receive radioiodine. Hyperthyroidism is cured in virtually all cases, although more than one dose of 131I may be required. However, the reduction in thyroid size is only partial, because of the presence of intrathyroidal calcifications, fibrosis, and large areas of nonfunctioning tissue. Nevertheless, in patients with large mediastinal goiters, but contraindications to surgery, radioiodine may be used with benefit and partial relieve of pressure symptoms. Prior to 131I administration, coexistent "cold” nodules must be submitted to fine needle aspiration cytology to exclude associated malignancy. Effective doses of 131I are relatively high in this condition. Post-radioiodine hypothyroidism is much less frequent than in toxic diffuse goiter, but may develop at any time after administration of 131I. Pretreatment with thionamides is recommended even in mild to moderate hyperthyroidism to avoid excessive relase of thyroid hormones after 131I. Surgery is generally regarded as a better option in patients with large goiters, especially if there is evidence of substernal extension and compression of airways and blood vessels. Surgery is also indicated in those instances when radioiodine uptake by the gland is relatively low, as frequently occurs in large multinodular goiters. Control of hyperthyroidism with antithyroid drugs and preoperative iodide is mandatory. Subtotal or near total thyroidectomy is indicated. Thus, hypothyroidism should be expected and adequate L-T4 treatment is required. We consider appropriate the use of partially suppressive doses of L-T4 to prevent recurrences. It is worth mentioning that surgical complications, such as laryngeal nerve paralysis and hypoparathyroidism, are more frequently observed in toxic multinodular goiters, especially if large and substernal, when compared to Graves' disease. |
