Radioiodine therapy after recombinant human tsh administration or hormone withdrawal: Is there a difference in I-131 effective half-life?

Abstract

Introduction The release of thyroidectomized patients treated with radioactive iodine I-131 from the treating facility is predominantly judged on the basis of the residual I-131 activity which is dictated by the effective half-life of I-131. Purpose To determine the effective half-life of I-131 (Teff1/2 in thyroidectomized patients subjected to radioiodine therapy after either recombinant human TSH administration or hormone therapy withdrawal. Materials and methods A series of 88 consecutive patients administered with I-131 following thyroidectomy was investigated. Recombinant human TSH has been administered in 32 patients (group A), while the rest 56 patients (group B) had been subjected to hormone therapy withdrawal. Measurements of the dose rate emitted by the patient at mid-thoracic height at a distance of 1 m were obtained 0, 6, 24 and 30 h after I-131 administration. The T1/2 was determined from the exponential fit of measured data. Data regarding age, sex, weight, height, diet, administered dose, volume of water drunk, and size of remnant thyroid tissue were recorded. Results The mean I-131 Teff1/2 was found 8.8 h for group A and 12.4 h for group B, with difference being statistically significantly (p Conclusion Administration of recombinant human TSH instead of hormone thyroid withdrawal prior to radioiodine therapy of thyroidectomized patients may enhance elimination rate of residual I-131 activity, and accelerate release from treating facility.