Levels of zinc and thymulin in plasma from patients with Crohn's disease.

Levels of zinc in plasma from patients with Crohn's disease were significantly lower than those of sex and age matched controls. We also measured the level of plasmic thymulin, a hormone released by the thymus gland, which in its active form binds one zinc molecule. The zinc unbound form of thymulin is biologically inactive and its level in the blood is a very sensitive marker of even marginal zinc deficiency. Levels of active thymulin were significantly reduced in plasma from patients with Crohn's disease, whereas plasma concentrations of the inactive form was higher than in controls. The in vitro addition of zinc ions restored thymulin activity in plasma from patients with Crohn's disease, and induced the disappearance of the inactive form. These findings suggest the existence of a zinc dependent alteration regarding the biological function of thymic hormones in patients with Crohn's disease. Such a defect might explain some of the immunological abnormalities observed in these pathological conditions.