Dose-dependent acute effects of recombinant human TSH (rhTSH) on thyroid size and function: comparison of 0·1, 0·3 and 0·9 mg of rhTSH

P>Context Recombinant human TSH (rhTSH) is used to augment the effect of radioiodine therapy for nontoxic multinodular goitre. Reports of acute thyroid swelling and hyperthyroidism warrant safety studies evaluating whether these side-effects are dose dependent. Objective To determine the effects on thyroid size and function of various doses of rhTSH. Design In nine healthy male volunteers, the effect of placebo, 0 center dot 1, 0 center dot 3 and 0 center dot 9 mg of rhTSH was examined in a paired design including four consecutive study rounds. Main outcome measures Main outcome measures were evaluated at baseline, 24 h, 48 h, 96 h, 7 days and 28 days after rhTSH and included: Thyroid volume (TV) estimation by planimetric ultrasound, and thyroid function by serum TSH, free T3, free T4 and Tg levels. Results Following placebo or 0 center dot 1 mg rhTSH, the TV did not change significantly from baseline at any time. At 24 and 48 h after administration of 0 center dot 3 mg rhTSH, the TV increased by 37 center dot 4 +/- 12 center dot 3% (SEM) (P = 0 center dot 03) and 45 center dot 3 +/- 16 center dot 1% (P = 0 center dot 05) respectively. After 0 center dot 9 mg rhTSH, the TV increased by 23 center dot 3 +/- 5 center dot 8% (P = 0 center dot 008) and 35 center dot 5 +/- 18 center dot 4% (P = 0 center dot 02) respectively. The increase in serum FT3, FT4 and thyroglobulin (Tg) was greater when administering 0 center dot 3 mg compared with 0 center dot 1 mg (P = 0 center dot 02) and when administering 0 center dot 9 mg compared with 0 center dot 3 mg (P = 0 center dot 02). After 0 center dot 1 mg rhTSH, the increase in FT3 and Tg was not significantly different from placebo whereas the FT4 increase was significantly higher (P = 0 center dot 02 compared with placebo). Conclusions In healthy individuals, rhTSH-induced thyroid swelling and hyperthyroidism is rapid and dose dependent. If valid for patients with goitre, our results suggest that these adverse effects are unlikely to be of clinical significance, following doses of rhTSH of 0 center dot 1 mg or less.