Toxic Adenoma medical therapy
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] ; Associate Editor(s)-in-Chief: Aditya Ganti M.B.B.S. [2]
Overview
The mainstay of treatment for most patients with toxic adenoma includes radioiodine, anti thyroid drugs.
Medical Treatment
In patients with overt thyrotoxicosis, beta blocker will alleviate the signs and symptoms mediated by the increased beta-adrenergic activity. The mainstay of treatment for most patients with toxic adenoma includes treatment with radioiodine and surgery. Alternative treatment modalities include percutaneous ethanol injection, thermoablation, or radiofrequency ablation. Antithyroid drugs are not routinely employed in the management of toxic adenoma.
RADIOACTIVE IODINE
In the United States, radioactive iodine is the preferred choice of treatment for patients with toxic adenoma.
Indications
Radioactive iodine is generally preferred over surgery when there is
- No suspicion of coexisting thyroid malignancy
- No large goiter threatening local compressive symptoms
- No other reason for neck surgery (e.g., primary hyperparathyroidism)
- No imperative for immediate cure, and whenever the patient’s general health makes him or her a poor candidate for surgery. <Ref>
Contraindications
- Pregnant women
- Children and adolescents(associated with risk of thyroid cancer)<ref>
The reported rates of overt hypothyroidism vary among studies between 0% and 35%. 15 The development of hypothyroidism was not associated with age, sex, radioiodine dose, radioiodine uptake, or degree of suppression of the extranodal tissue. The predictors of occurrence of hypothyroidism were pretreatment with antithyroid medications and a positive thyroid antibody status. Antibody-positive patients showed an earlier occurrence of hypothyroidism than did antibody-negative patients, 15 suggesting that the autoimmunity added to damage to the thyroid gland. Moreover, these results suggest that longer follow-up periods may uncover hypothyroidism more frequently. In patients treated with antithyroid drugs prior to radioiodine therapy, the increase in TSH may reactivate suppressed thyroid tissue and iodide uptake, resulting in damage by 131 iodine. Therefore, some clinicians administer levothyroxine for 2 weeks prior to therapy in order to assure that the tissue surrounding the toxic adenoma is suppressed. In some instances, high doses of 131 iodine in the nodule may provide enough radiation to the surrounding tissue that its function is seriously damaged.
It is noteworthy that therapy with 131 iodine may trigger the development of anti-TSH receptor autoantibodies. 16 For example, about 5% of patients treated with 131 iodine for toxic or euthyroid multinodular goiter develop stimulating TSH receptor antibodies and Graves’ disease. 17 Hence, hypothyroidism may, in part, result from the development of humoral autoantibodies in patients with toxic adenomas treated with 131 iodine.
Percutaneous ethanol injection
An alternative to surgery and 131 iodine therapy for toxic adenomas is the use of percutaneous ethanol injection into the nodule under ultrasound guidance. 8 18
- The injection results in necrosis and thrombosis of small vessels.
- Side effects include local pain and, in rare cases, recurrent nerve damage. 19 20
- Results of ethanol injection in relatively large AFTNs (diameter 3 to 4 cm) are also favorable, particularly in patients with subclinical hyperthyroidism. 21
Percutaneous laser thermal ablation (LTA)
- Percutaneous laser thermal ablation (LTA) is a more recently introduced technique for the treatment of thyroid nodules. 22
- In hyperfunctioning nodules, LTA induced a nearly 50% volume reduction with a variable frequency of normalization of thyroid-stimulating hormone levels. 23 24
- Ultrasound-guided laser or radiofrequency ablation are also used for symptomatic solid nodules with normal or abnormal thyroid function and appear safe and effective. 25 Newer techniques, whose clinical utility need further characterization, include microwave ablation and high-intensity focused ultrasound. 25
Complications
Potential adverse effects of 131 I therapy for toxic nodular goiter include
- Radiation thyroiditis
- Postablative hypothyroidism.
Radiation thyroiditis
- Radiation thyroiditis presents with anterior neck pain in the week after therapy and exacerbation of thyrotoxicosis because of the release of preformed thyroid hormone from the gland, which typically occurs 2 to 8 weeks after treatment.
- Pretreatment with an antithyroid drug has been shown to decrease the severity of thyrotoxicosis caused by radiation thyroiditis in Graves’ disease, 132 133 134 135 but this has not been established for toxic nodular goiter.
- Thyroiditis-related gland swelling with potential worsening of compressive symptoms is a concern that has not actually been realized in studies of radioiodine therapy for nodular goiter. 136 137
- Long term, thyroid volume typically decreases by about 40% after 131 I treatment. 138 139
Postablative hypothyroidism
- The incidence of postablative hypothyroidism after radioiodine therapy has been reported to be 25% to 50%, which is lower than that encountered after treatment of patients with Graves’ disease.
- This is presumably because suppressed extranodular thyroid tissue does not take up radioiodine.
- Radioisotopic distribution within functioning tissue can also be heterogeneous.
- Postablative hypothyroidism is more common when higher doses of radioactive iodine are administered.
ANTITHYROID DRUGS
- Unlike hyperthyroid Graves’ disease, thyroid autonomy in toxic nodular goiter rarely remits unless it has been provoked by an iodine load.
- Thionamide therapy alone may not control hyperthyroidism completely because of the substantial store of previously synthesized thyroid hormone that can be present in the large gland of a patient with toxic nodular goiter.
- But still antithyroid medications are indicated in situations which include
- Useful for the initial control of hyperthyroidism that is severe or complicates cardiac or other conditions in a fragile patient.
- PTU is the immediate treatment of choice for pregnant patients with hyperthyroidism.
- Time-limited course of antithyroid drugs can sometimes be useful to evaluate the clinical status of patients with subclinical hyperthyroidism who have nonspecific symptoms, such as nervousness or insomnia, that may or may not improve with definitive treatment of mild hyperthyroidism.
- If a patient experiences an improvement in symptoms or sense of well-being when thyroid function has been restored to normal on thionamide therapy, then radioiodine therapy or surgery is indicated.