We acknowledge that corticosteroid use may reflect more active disease, and indeed was part of our definition of PNR, so the association between fT3/fT4 ratio and corticosteroids may be a combination of the direct effect of the corticosteroids on the hypothalamic–pituitary–thyroid axis and more severe IBD, as evidenced by raised CRP and higher faecal calprotectin concentrations. The gene discussed is CRP; the disease is inflammatory bowel disease.