In sputum cells of COPD patients, HAMP expression was increased relative to healthy controls with no difference demonstrated between patients with high and low intracellular iron (1.40 [0.94,4.30] vs. 2.34 [1.70,8.00] fold difference, p = 0.09, Mann–Whitney test, Fig. 2a). This evidence concerns the gene HAMP and chronic obstructive pulmonary disease.