nutritional disorders
Zinc Deficiency
Introduction
Zinc (Zn) is contained mainly in bones, teeth, hair, skin, liver, muscle, leukocytes, and testes. Zinc is a component of several hundred enzymes, including many nicotinamide adenine dinucleotide (NADH) dehydrogenases, RNA and DNA polymerases, and DNA transcription factors as well as alkaline phosphatase, superoxide dismutase, and carbonic anhydrase. (See also Overview of Minerals .) A diet high in fiber and phytate (eg, in whole-grain bread) reduces zinc absorption. Dietary deficiency is unlikely in healthy persons. Secondary zinc deficiency can develop in the following: Patients taking diuretics Patients with Diabetes Mellitus (DM) , Patients with stressful severe acute conditions (eg, sepsis, burns, head injury) Older institutionalized and homebound patients (common) Maternal zinc deficiency may cause fetal malformations and low birth weight. Zinc deficiency in children causes impaired growth, impaired taste (hypogeusia) and smell, delayed sexual maturation, and hypogonadism and oligospermia in men. In children or adults, manifestations also include alopecia, impaired immunity, anorexia, dermatitis, night blindness, anemia, lethargy, and impaired wound healing. Zinc deficiency during pregnancy may result in a low birth weight and preterm birth. Clinicians should suspect zinc deficiency in undernourished patients based on typical symptoms or signs and their response to zinc supplements. However, because many of the symptoms and signs are nonspecific, clinical diagnosis of mild zinc deficiency is difficult.Biotin,riboflavin, and essential fatty acid deficiencies may resemble zinc deficiency. Laboratory diagnosis is also difficult, requiring special collection techniques. Lowalbuminlevels, common in zinc deficiency, make serum zinc levels difficult to interpret; urine zinc levels are unreliable for acute deficiency, as are hair zinc levels. If available, isotope studies can measure zinc status more accurately. Treatment of zinc deficiency consists of elemental zinc 1 to 3 mg/kg orally once a day until symptoms and signs resolve. 