Goals And Expected Outcomes Of Treatment

With adequate doses of radioactivity, an 80% response rate should be expected. A primary goal of treatment is to resolve hyperthyroidism in as short a time as possible. However, with RAI doses calculated to achieve this goal in the majority of patients, a significant number of patients will ultimately become hypothyroid. The incidence of hypothyroidism was first estimated at 20% to 40% of patients one year after RAI therapy (30). With more conservative doses of RAI, the incidence of hypothyroidism may be lower, although, often at the expense of higher rates of persistent hyperthyroidism. Patient preferences, the availability of close follow-up, and potential risks from persistent hyperthyroidism should be considered when deciding between more definitive treatment with higher doses and the use of more conservative doses.

Some authorities have maintained that hypothyroidism, which is easily and inexpensively treated with thyroid hormone supplementation, is preferable to persistent hyperthyroidism, which, if not optimally treated, may produce significant morbidity. It is also commonly believed that hypothyroidism may be a frequent long-term consequence of autoimmune thyroid disease. This has led to the recommendation for higher treatment doses to reduce the need for additional treatments in patients who do not respond to initial treatments. If hypothyroidism is regarded as a potential therapeutic endpoint, patients should be given the understanding that they will likely require life-long thyroid hormone supplementation to maintain normal function in the future.

Hypothyroidism tends to occur more frequently in patients with small thyroid glands and lower 24-hour uptake measurements (31). Other independent predictors of hypothyroidism following RAI treatment include a diagnosis of GD, the level of thyroid autoantibodies, no antithyroid treatment given prior to RAI, nonpalpable goiter, and high RAI dose. In one series, the absence of these risk factors was associated with a 12% probability of developing hypothyroidism, whereas with all factors, the probability increases to 96% (32). Hypothyroidism may occur several years following RAI treatment, and may be more likely in patients who have had multiple RAI treatments (33). Regardless of whether the goal is to achieve euthyroidism or acceptable rates of hypothyroidism, all patients who have been treated with RAI should receive longitudinal clinical follow-up along with thyroid function studies. Patients with autoimmune thyroid disease should also be monitored for complications, such as Graves' opthalmopathy.

In addition to abolishing hyperthyroidism, treatment with radioiodine should significantly reduce thyroid gland size in patients with GD. A 50% to 80% reduction in gland volume may be seen in proportion to the radiation dose given (34).

0 0

Post a comment