Zinc

Zinc (Zn) is an essential trace element required for normal growth and maturation, as it is a component of many enzymes and protein structures. Most circulating zinc (80%) is present in the red cells. A similar proportion of plasma zinc is albumin bound, the remainder being bound to alpha-2-macroglobulin, although a small percentage is present as amino acid complexes.

Acute zinc deficiency may occur during catabolic processes (following surgery, infections etc.) or TPN with inadequate supplementation; the symptoms including a characteristic rash, abdominal pain and diarrhoea with depression and lethargy. Zinc deficiency may be associated with poor wound healing. Acrodermatitis enteropathica is a rare, autosomal recessive, inherited defect of zinc absorption, which presents with similar symptoms shortly after weaning. Zinc supplementation can result in copper deficiency and vice versa.

Plasma/serum zinc is the simplest means of assessing zinc status, but concentrations may be affected by diet (fasting leads to an increase), diurnal variation (peak around 10:00h), albumin concentrations, acute phase response (increased copper, decreased zinc), steroid therapy and pregnancy (decrease).