Thereafter, either 10 ml NaCl 0.9% or 100µg CRF topped up to 10ml with NaCL 0.9% (according to randomisation) will be injected intravenously. Endoscopist and assistant staff will be blinded to the randomisation. Subsequently, the gut surface will be examined for at least 5 min with endomicroscopy for any change in IEL, epithelial breaks/gaps with extrusion of fluorescein into the gut lumen and widening of intervillous space.