In 995 patients with Crohn’s disease from the PANTS study, lower baseline serum fT3/fT4 ratio was independently associated with female sex, higher inflammatory burden at baseline, and baseline corticosteroid use, and predicted primary non‐response to anti‐TNF therapy at week 14, but not non‐remission or change in faecal calprotectin concentrations at week 54. This evidence concerns the gene TNF and Crohn disease.