Mean (± SD) levels of iodothyronines in blood plasma of control X. laevis and larvae exposed to each of three model thyroperoxidase inhibitors during pro-metamorphosis at 2, 4, 7 and 10 d post NF 53/54. Sample sizes are n = 3 pools except for the high PTU treatment which has a sample size of n = 2 pools. Treatments with evidence of a difference with the control (FDR-adjusted p < 0.05) are indicated with an asterisk (*). T4, thyroxine; T3, triiodothyronine; MMI, methimazole; MBT, mercaptobenzothiazole; PTU, propylthiouracil; MMI:Low, 55 μM; MMI:Med, 110 μM; MMI:High, 220 μM; MBT:Low, 0.18 μM; MBT:Med, 0.54 μM; MBT:High, 1.6 μM; PTU:Low, 13 μM; PTU:Med, 39 μM; PTU:High, 117.5 μM.