Zinc (Zn)

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Subject: Zinc (Zn)

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Definition

  • Zinc, an essential trace element, is the intrinsic metal component or activating cofactor for more than 70 important enzyme systems, including carbonic anhydrase, the ALPs, dehydrogenases, and carboxypeptidases. It is involved in the regulation of nucleoproteins and the activity of various inflammatory cells and plays a role in growth, tissue repair and wound healing, carbohydrate tolerance, and synthesis of testicular hormones. Zinc intake is closely related to protein intake; as a result, it is an important component of nutritionally related morbidity worldwide. Symptoms attributable to severe zinc depletion include growth failure, primary hypogonadism, skin disease, impaired taste and smell, and impaired immunity and resistance to infection. Subclinical zinc deficiency may significantly increase the incidence of and morbidity and mortality from diarrhea and upper respiratory tract infections. Along with iron, iodine, and vitamin A, zinc deficiency is one of the most important micronutrient deficiencies globally. Several studies have now demonstrated that supplementation of high-risk populations can have substantial health benefits.

  • Normal range: (see Table 16.89).

 
TABLE 16–89
Normal Range for Zinc by Age

Use

  • Detecting zinc deficiency

  • Assist in confirming acrodermatitis enteropathica

  • Evaluate nutritional deficiency

  • Evaluate possible toxicity

  • Monitor replacement therapy in individuals with identified deficiencies

  • Monitor therapy of individuals with Wilson disease

Interpretation

Increased In

  • Anemia

  • Arteriosclerosis

  • Coronary heart disease

  • Primary osteosarcoma of the bone

Decreased In

  • Acrodermatitis enteropathica

  • AIDS

  • Acute infections

  • Acute stress

  • Burns

  • Cirrhosis

  • Conditions that decrease albumin

  • Diabetes

  • Long-term TPN

  • Malabsorption

  • Myocardial infarction

  • Nephrotic syndrome

  • Nutritional deficiency

  • Pregnancy

  • Pulmonary TB

  • Ulcerative colitis, Crohn disease

  • Regional enteritis, sprue, intestinal bypass, neoplastic disease

  • Increased catabolism induced by anabolic steroids

Limitations

  • Plasma levels of zinc do not necessarily correlate with tissue levels and do not reliably identify individuals with zinc deficiency. Although plasma levels are generally a good index of zinc status in healthy individuals, these levels are depressed during inflammatory disease states.

  • Erythrocyte concentrations of zinc may provide a more useful measure of zinc status during acute or chronic inflammation. Several functional indices also can be used to indirectly assess zinc status. Serum superoxide dismutase and erythrocyte alkaline phosphatase activities have been proposed as indirect markers of zinc status, but these tests are not widely available.

  • The conditions of anorexia and starvation also result in low zinc levels.

  • Hemolyzed specimens cause false elevation of serum zinc levels.

  • Specimens should be collected in metal-free specimen containers.

  • Auranofin, chlorthalidone, corticotropin, oral contraceptives, and penicillamine increase zinc levels.

  • Anticonvulsants, cisplatin, citrates, corticosteroids, estrogens, interferon, and oral contraceptives decrease zinc levels.

 
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