Antithyroid Pretreatment Research Articles

Long-term effect of radioactive iodine on thyroid function and size in patients with solitary autonomously functioning toxic thyroid nodules.

To investigate the long-term effects of radioiodine (131I) on thyroid function and size in patients with a solitary toxic thyroid nodule. Prospective study of patients treated for a solitary autonomous toxic nodule, followed by evaluation of thyroid volume and function. Sixty-two consecutive patients followed for a minimum of 12 months (range 12-168, median 60). Seventeen patients received antithyroid drug treatment before 131I. Standard thyroid function variables and ultrasonically determined thyroid volume before as well as 0.75, 1.5, 3, 6 and 12 months after treatment, and then once a year were investigated. 131I treatment (3.7 MBq/g thyroid tissue corrected to a 100% 24-h 131I uptake) was given as a single dose in 53 patients; six needed two doses and another three were given 3-5 131I treatments. The median initial dose was 310 MBq (140-666) and the median total dose was 332 MBq (148-1576). In patients receiving one 131I treatment (n = 53) the total thyroid volume decreased significantly from a median of 40 ml (range 19-77) to 24 ml (8-50) within 3 months. This represented a median reduction of 35%. A further significant decrease was seen after 24 months to a total reduction of 45%. In patients given more than one dose the thyroid volume was reduced from a median of 45 ml (19-104) before treatment to 30 ml (14-50) after a follow-up of 60 months (9-132) after the last 131I treatment. Patients without antithyroid pretreatment, receiving one 131I treatment (n = 39) became euthyroid after a median of 1.5 months (0.75-9) after treatment. Seventy-five per cent were euthyroid within 3 months. In patients pretreated with antithyroid drugs and treated with one dose of 131I (n = 14) euthyroidism was achieved after a median of 12 months (0.75-24) after 131I treatment. Hypothyroidism developed in five patients (8%) after a median of 36 months (6-60) after 131I treatment. A cure-rate of 75% within 3 months is seen when treating autonomous solitary toxic thyroid nodules with 131I. The thyroid volume is reduced by 35% within 3 months and 45% after 2 years. Side-effects are few and consist of hypothyroidism in less than 10% with a median follow-up of 5 years. This treatment should be regarded as the standard treatment for this condition until prospective comparisons with surgery and ethanol injection therapy have been performed.

Changes in the thyroid technetium-99m scintigram after antithyroid and subsequent radioiodine treatment for solitary autonomous nodules.

In patients with solitary autonomous thyroid nodules, the treatment of choice is radioiodine (131I) therapy, eventually preceded by antithyroid drugs to avoid aggravation of hyperthyroidism. The aim of this study was to evaluate the scintigraphical results of 131I treatment when using antithyroid pretreatment. Twenty-four patients having a solitary autonomous thyroid nodule were studied. A technetium-99m (99mTc) pertechnetate scintigraphy was performed at the time of diagnosis, when serum thyrotropin (TSH) had been normal for about 3 months on antithyroid drug treatment, and finally when serum TSH was normalized after 131I treatment. The primary scintigram showed suppression of 99mTc pertechnetate in the paranodular thyroid tissue in all patients. The second scintigram showed normal uptake in the paranodular tissue in 22 patients and a continuing suppression of the paranodular tissue in 2 patients. The third scintigram showed a solitary adenoma in 14 patients with none or almost no uptake in the paranodular tissue, resembling the first scintigram. In 6 patients an adenoma was still present, but uptake was seen in the paranodular tissue; in 3 patients a homogenous uptake without any sign of the previous nodule, and in 1 patient very low uptake in the gland was seen. Four patients developed hypothyroidism in the follow-up period of approximately 1 year. Pretreatment with antithyroid drugs induced an increase in serum TSH, stimulating the paranodular tissue. 131I will therefore be distributed in the whole thyroid gland, and not only in the autonomous solitary nodule. After 131I treatment, we continuously found a solitary nodule with low uptake in the paranodular tissue in 20 of 24 patients.