DIO1 and hypothyroidism: The observed reductions in T3 and T4, along with the transcriptional down-regulation of Dio1 mRNA (Supplementary Figure S4 at http://www.biochemj.org/bj/453/bj4530071add.htm), which is known to be down-regulated in cases of hypothyroidism, indicated that the livers of the treated rats were in a hypothyroid state [17,50].