¹²³I Thyroid Uptake and Thyroid Size at 24, 48, and 72 Hours after the Administration of Recombinant Human Thyroid-Stimulating Hormone to Normal Volunteers

Abstract

Context: Recombinant human TSH (rhTSH) is used to evaluate thyroid carcinoma patients and off-label for 131 I thyroid ablation and nontoxic goiter therapy.Objective: Our objective was to determine the optimal time for 131 I administration after rhTSH.Participants: Twenty-five euthyroid nongoitrous volunteers participated in the study.Design: Baseline 24-h thyroid 123 I uptake (RAIU) was measured, and then 0.1 mg rhTSH was administered.123 I was administered 24, 48, or 72 h after rhTSH, and a repeat 24-h RAIU was obtained. Setting:The study was conducted at an academic research center. Main Outcome Measures:Thyroid function tests, thyroid ultrasounds, and electrocardiograms were measured before rhTSH, then daily for 4 d, and finally 7 d after rhTSH.Results: Serum TSH concentrations 24 h after rhTSH increased from 1.7 Ϯ 0.5 U/ml (mean Ϯ SD) to 13.3 Ϯ 4. The 24-h RAIUs rose from 25 Ϯ 5 to 47 Ϯ 8% (88% increase) when the 123 I was given at 24 h after rhTSH and from 29.8 Ϯ 7 to 40.5 Ϯ 13% (36% increase) when the 123 I was given at 48 h and were unchanged when the 123 I was given at 72 h. The post-rhTSH RAIU increase was greater at 24 than at 72 h (P Ͻ 0.005) and marginally greater than at 48 h (P ϭ 0.057). Thyroid volumes significantly increased 48 h after rhTSH (10 Ϯ 3.8 vs. 11.1 Ϯ 3.7 ml; P Ͻ 0.009). Electrocardiograms were normal. Conclusions

Optimizing 131I Uptake After rhTSH Stimulation in Patients with Nontoxic Multinodular Goiter: Evidence from a Prospective, Randomized, Double-Blind Study

“…Our results indicate that the response to rhTSH in goiter patients, compared with healthy individuals, may differ. Although we observed a similar trend (the effect of rhTSH decreased with intervals longer than 24 h), we found that the RAIU was still significantly increased (by 62%) in the rhTSH/72-h group, in contrast to no response seen in healthy individuals (7). Apparently the morphologic or physiologic changes in goiter tissue cause a prolonged effect of rhTSH on RAIU.…”

“…In an uncontrolled trial including 25 healthy individuals (7)-also using 0.1 mg of rhTSH-the same intervals (24,48, and 72 h) between rhTSH and 131 I tracer administration were investigated. In that study (7), the relative increase in 24-h RAIU was 88%, 36%, and 0%, respectively, in the 24-, 48-, and 72-h rhTSH groups. Our results indicate that the response to rhTSH in goiter patients, compared with healthy individuals, may differ.…”

“…Recombinant human thyroid-stimulating hormone (rhTSH) increases the thyroid RAIU by approximately 100% in both healthy individuals (7,8) and goiter patients (9)(10)(11)(12)(13). In 3 randomized controlled trials (13)(14)(15), rhTSH has been documented to enhance the goiter volume reduction by 35%256% when standard 131 I activities are used.…”

Time to reconsider nonsurgical therapy of benign non-toxic multinodular goitre: focus on recombinant human TSH augmented radioiodine therapy

“…Defining a lower dose limit that increases RAIU sufficiently is paramount, since adverse effects, especially the induction of transient thyrotoxicosis, are dose dependent (40)(41)(42). The changes in thyroid RAIU following rhTSH doses between 0.01 and 0.9 mg have been investigated in both healthy individuals and patients with MNG (Table 1).…”

“…In addition, measurements of RAIU are extremely prone to variation in the method used. Despite these shortcomings, studies in MNG patients (19,20,40,(43)(44)(45)(46) and healthy individuals (41,42,47) document an approximately twofold increase in RAIU, largely independent of rhTSH dose. In support of this observation, a small comparative trial found that 0.03 mg was not superior to 0.01 mg (40) and another comparative trial observed that 0.3 mg was not superior to 0.1 mg (45).…”