Abstract
Background: Recombinant human thyrotropin (rhTSH) approximately doubles thyroid radioiodine uptake (RAIU) in patients with nontoxic nodular goitre (NTNG), at large independent of rhTSH dose.
Aim: To evaluate the optimal time interval (24h, 48h or 72h) for rhTSH injection to enhance RAIU.
Methods: Randomized placebo-controlled, double-blinded study in a two-factorial design. Eighty-one (70 females, median age 52, range 22-83 years) patients with benign NTNG were randomized to either 0.1 mg rhTSH or isotonic saline, and furthermore to a time interval of 24h, 48h, or 72h before 131I-tracer administration. The rhTSH/placebo stimulated RAIU was performed four weeks after a baseline RAIU, determined at 24h and 96h.
Results: Mean baseline RAIU was 34.5% ± 1.2% (SE), and did not differ significantly in any of the groups. No change was seen in any of the placebo subgroups. In the rhTSH/24h group, the increase in 24h and 96h RAIU was 122% (95% CI, 87-157%) and 108% (95% CI, 74-142%), respectively. It was 97% (95% CI, 62-132%) and 82% (95% CI, 60-104%), respectively, in the rhTSH/48h group and 61% (95% CI, 36-85%) and 52% (95% CI, 28-75%), respectively, in the rhTSH/72h group. All increases were highly significant (p<0.0001). The RAIU increase was greater after rhTSH/24h than after rhTSH/72h (p=0.023) and insignificantly higher than after rhTSH/48 hours (p=0.512).
Conclusions: The increase in RAIU in nontoxic goitre patients after stimulation with rhTSH seems to be time dependent, with a waning effect if the time interval exceeds 24h. However, in contrast to healthy individuals (S. Pena et al., 2006) the effect is still pronounced after 72 hours. The importance of this timing in the context of 131-I therapy should be explored.