Factors underlying abnormal zinc metabolism in uremia

Zinc balance studies were completed in ten hemodialyzed adult uremic patients and five normal controls to determine the cause of abnormal zinc metabolism in uremia. Subjects were fed standard hospital foods providing nutrients in amounts recommended for adult stable hemodialyzed patients. The amount of zinc in the diet was kept constant at 10 mg per day. After one week of stabilization, blood, urine, used dialysate (in patients on dialysis days) and stool samples were collected daily for the next two weeks. In comparison to controls, patients had lower plasma zinc levels (mean +/- SD, 112 +/- 10 vs. 82 +/- 12 micrograms/dl, P less than 0.01), lower urinary zinc excretion (560 +/- 120 vs. 40 +/- 20 mg/24 hrs, P less than 0.001) and higher fecal zinc losses (8.1 +/- 0.7 vs. 10.2 +/- 0.6 mg/24 hrs, P less than 0.01). Dialytic zinc losses were minimal (26 +/- 4 micrograms/treatment). During the study period, patients were in a negative zinc balance while normal controls maintained a positive zinc balance on 10 mg dietary zinc intake. These results demonstrate that augmented fecal zinc excretion in the presence of hypozincemia contributes to the negative zinc balance in hemodialyzed uremic patients.

Nucleotides in lymphocytes of human subjects with zinc deficiency

Cell-mediated immunity in human subjects is affected adversely as a result of zinc deficiency. The mechanism by which a deficiency of zinc may affect lymphocyte proliferation and functions, is not well understood at present. Nucleoside phosphorylase (NPase), a purine catabolic pathway enzyme, is zinc dependent, and a congenital deficiency of this enzyme is known to affect adversely cell-mediated immunity. This effect has been related to an accumulation of toxic nucleotides in lymphocytes as a result of NPase deficiency. Inasmuch as the effect of zinc deficiency on the activity of NPase and the levels of nucleotides in human lymphocytes has not been previously reported, we assayed these parameters in human subjects with zinc deficiency before and after zinc supplementation. A mild deficiency of zinc was diagnosed in those having decreased zinc in two out of three cell lineages (less than 42 micrograms in granulocytes, less than 48 micrograms in lymphocytes, and less than 1.70 microgram in platelets, per 10(10) cells). In comparison with five subjects with sufficient zinc, six subjects with zinc deficiency showed a decrease in the activity of NPase (p = 0.01), an increase in adenosine diphosphate (ADP) level (p = 0.008), a decreased adenosine triphosphate (ATP)-to-ADP ratio (p = 0.0001), and an increase in both guanosine triphosphate (GTP) (p = 0.02) and deoxyadenosine triphosphate (dGTP) (p = 0.04 in the lymphocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

Net renal tubular reabsorption of zinc in healthy man and impaired handling in sickle cell anemia

Zinc deficiency is a significant clinical finding in sickle cell anemia (SCA) and abnormalities of zinc handling such as hyperzincuria are present. The cause of increased urinary zinc excretion in SCA is not clear. To define the renal handling of zinc in SCA and in healthy subjects, we measured zinc (total and ultrafilterable plasma zinc, urine zinc) and creatinine clearance in eight healthy and seven SCA subjects. Ultrafilterable zinc in plasma was assessed by equilibration of plasma with 65Zn followed by filtration through Amicon Cetriflo CF25 cones. While the mean filtered load of zinc was not significantly different between the two groups, the mean zinc excretion rate was approximately three-fold higher in patients (1.73 +/- 0.96 vs. 0.63 +/- 0.39 micrograms/min, P less than .05). In controls, zinc excreted was significantly less than zinc filtered (P less than .005), the fractional excretion of zinc averaging 0.49 +/- 0.31, indicating net reabsorption. This was not the case for the SCA patients. We conclude that there is impaired renal tubular handling of zinc in SCA.

Zinc absorption in human small intestine

We determined the intestinal site of zinc absorption in humans and investigated the interaction between intestinal absorption of zinc and other solutes using the triple-lumen steady-state perfusion technique. Twenty-one healthy subjects participated in the study. During intestinal perfusion of a balanced electrolyte solution containing 0.1 mM zinc acetate, zinc absorption occurred throughout the entire small intestine. However, the jejunum had the highest rate of absorption (357 +/- 14 nM.min-1.40 cm-1) compared with the duodenum (230 +/- 33 nM.min-1.40 cm-1) and ileum (84 +/- 10 nM.min-1.40 cm-1). Over a range of zinc concentrations infused into the jejunum (0.1, 0.9, and 1.8 mM) there were linear increases in the rate of zinc absorption (P less than 0.05). Intestinal absorption of zinc was significantly stimulated by the addition of glucose (20 mM). Zinc absorption increased from 459 +/- 39 to 582 +/- 45 nM.min-1.40 cm-1 (P less than 0.05). Conversely, zinc (0.9 mM) also enhanced the absorption of glucose, which was increased from 293 +/- 43 to 447 +/- 27 microM.min-1.40 cm-1 (P less than 0.05). The enhanced absorption of zinc or glucose was not accompanied by any increase in absorption of water and sodium. In contrast, increasing the concentration of zinc in the perfusate resulted in decreased absorption of sodium and water in a dose-related manner. In conclusion, our study demonstrated that zinc absorption is concentration dependent and occurs throughout the small intestine. The jejunum has the highest rate of absorption of zinc. The interactions between absorption of zinc and other solutes suggest that the transport process of zinc is carrier mediated.

Serum thymulin in human zinc deficiency

The activity of thymulin (a thymic hormone) is dependent on the presence of zinc in the molecule. We assayed serum thymulin activity in three models of mildly zinc-deficient (ZD) human subjects before and after zinc supplementation: (a) two human volunteers in whom a specific and mild zinc deficiency was induced by dietary means; (b) six mildly ZD adult sickle cell anemia (SCA) subjects; and (c) six mildly ZD adult non-SCA subjects. Their plasma zinc levels were normal and they showed no overt clinical manifestations of zinc deficiency. The diagnosis of mild zinc deficiency was based on the assay of zinc in lymphocytes, granulocytes, and platelets. Serum thymulin activity was decreased as a result of mild zinc deficiency and was corrected by in vivo and in vitro zinc supplementation, suggesting that this parameter was a sensitive indicator of zinc deficiency in humans. An increase in T101-, sIg-cells, decrease in T4+/T8+ ratio, and decreased IL 2 activity were observed in the experimental human model during the zinc depletion phase, all of which were corrected after repletion with zinc. Similar changes in lymphocyte subpopulation, correctable with zinc supplementation, were also observed in mildly ZD SCA subjects. Inasmuch as thymulin is known to induce intra- and extrathymic T cell differentiation, our studies provide a possible mechanism for the role of zinc on T cell functions.

Zinc in growth and development and spectrum of human zinc deficiency

Growth retardation is seen in experimental animals as a result of severe dietary restriction of several essential trace elements. However, in humans, the effect of zinc deficiency is most pronounced. Growth failure and hypogonadism in males, related to a deficiency of zinc, have been recognized in many developing countries. A mild deficiency of zinc, affecting growth and development in children and adolescents, has been reported from developed countries as well. Zinc deficiency in humans may manifest as severe, moderate, or mild. The manifestations of severe zinc deficiency include bullous pustular dermatitis, alopecia, diarrhea, emotional disorder, weight loss, intercurrent infections due to cell-mediated immune dysfunctions, hypogonadism in males, neurosensory disorders, and problems with healing of ulcers. This condition can be fatal. A moderate level of zinc deficiency has been reported in a variety of conditions. Clinical manifestations include growth retardation and male hypogonadism in adolescence, rough skin, poor appetite, mental lethargy, delayed wound healing, cell-mediated immune dysfunctions, and abnormal neurosensory changes. A mild level of zinc deficiency may manifest with decreased serum testosterone level and oligospermia in males, decreased lean body mass, hyper-ammonemia, neurosensory changes, anergy, decreased serum thymulin activity, and decreased IL-2 activity. Although the clinical aspects of severe and moderate levels of zinc deficiency are well known, the recognition of mild levels of zinc deficiency has been difficult. Currently plasmas zinc appears to be the most widely used parameter for assessment of human zinc status, and it is known to be decreased in cases of severe and moderate deficiency of zinc.(ABSTRACT TRUNCATED AT 250 WORDS)

Recurrent pneumothoraces in miliary tuberculosis

An 18-year-old female patient with miliary tuberculosis presented with bilateral, simultaneous pneumothoraces, which were recurrent with a bronchopleural fistula. The recurrent pneumothoraces were managed with tube thoracostomy and pleurodesis. Various possible pathogenetic mechanisms of this rare complication are discussed.

Cell cycle distribution defect in PHA-stimulated T lymphocytes of sickle cell disease patients

T lymphocytes from normal human controls and sickle cell disease (SCD) patients were isolated from peripheral blood and cultured for 72 hours following addition of phytohemagglutinin. The ratio for the fraction of cells in DNA synthesis (S phase) over the fraction in G2 phase (S/G2) was significantly higher in SCD patients in comparison to the controls (mean +/- SD) (4.01 +/- 0.78 vs. 2.78 +/- 0.76, P less than 0.02). Following in vivo zinc supplementation to two subjects, the S/G2 ratio was normalized. We conclude that the distribution of T lymphocytes in cell cycle is altered in SCD patients and that this effect may be zinc-dependent.

Zinc tolerance test in uremia: effect of calcitriol supplementation

The effect of 1,25(OH)2D3 on zinc absorption was indirectly determined in hemodialysis patients using the oral zinc tolerance test. The increment in plasma zinc and the area under the curve following an oral zinc load of 25 mg were studied in seven patients, before and after 6 weeks of therapy with 1 microgram/day of 1,25(OH)2D3 [Rocaltrol(R)]. Before therapy, fasting plasma zinc, 2 hour plasma zinc, and the area under the curve (AUC) were subnormal (hemodialysis patients vs normals: 96 +/- 2 vs 105 +/- 3 micrograms/dl, p less than 0.05, 161 +/- 8 vs 222 +/- 16 micrograms/dl, p less than 0.025, and 188 +/- 25 vs 302 +/- 33 micrograms hr/dl, p less than 0.025, respectively). Following Rocaltrol, serum calcium level increased (8.9 +/- .12 to 9.8 +/- .4 mg/dl, p less than 0.05), parathyroid hormone levels decreased (20.4 +/- 8.9 to 13.6 +/- 7.2 ng/ml, p less than 0.05), but there was no significant change in fasting plasma zinc, 2 hour plasma zinc, or AUC (89 +/- 3 micrograms/dl, 149 micrograms/dl, and 176 +/- 18 micrograms hr/dl, respectively). These results suggest that short-term 1,25(OH)2D3 therapy had no significant impact on zinc absorption or plasma zinc level in uremics.

Elevated plasma copper in chronic renal failure

Hypercupremia has been described in patients undergoing chronic dialysis. To further characterize dialysis-associated hypercupremia, we studied plasma copper (PCu) and ceruloplasmin (Cp) in patients on hemodialysis (n = 20) and peritoneal dialysis (n = 25), in uremic patients (n = 10) not yet on dialysis, and in normal age-matched control subjects (n = 20). PCu was significantly elevated in all three patients groups (mean +/- SD) (20.6 +/- 4.1, 19.8 +/- 4.6, 19.8 +/- 4.9 mumol/L, respectively) vs control subjects (16.5 +/- 2.7 mumol/L). However, Cp levels were not significantly different among the four study groups (330 +/- 60, 320 +/- 70, 370 +/- 100, and 360 +/- 90 mg/L, respectively). Calculated nonceruloplasmin copper was significantly higher in all uremic groups. The measurement of chelatable Cu confirmed the presence of significantly higher extractable Cu in hemodialysis (2.7 +/- 0.6 mumol/L) and peritoneal dialysis patients (2.4 +/- 0.5 mumol/L) than control subjects (1.5 +/- 0.3 mumol/L). Cu is elevated in uremia regardless of dialysis status and this elevation is not accounted for by an increase in plasma ceruloplasmin.

Dietary model for production of experimental zinc deficiency in man

A semipurified diet based on soy protein was developed to induce mild zinc deficiency in five male volunteers. Each of seven daily menus provided (mean +/- SD) 2248 +/- 128 kcal, 56.6 +/- 5.7 protein, 261 +/- 30 g carbohydrate, 110 +/- 21 g fat, 8.5 +/- 1.4 g fiber, and 4.8 +/- 1.3 mg zinc. The analytical value for phytate:zinc molar ratio was 21 +/- 9. One subject, who received five of the menus for 28 wk, lost approximately 200 mg body zinc and 7% weight; zinc concentration declined 25% in plasma, 30% in lymphocytes, and 55% in neutrophils. This dietary model allowed simple formulation of new menus for subjects in diverse states of health. It caused no ill effects after prolonged consumption, and all deficiency symptoms were reversed by zinc supplementation of 30 mg/d for 20 wk. With simple manipulation, this dietary model may be used safely for gradual induction of zinc and/or other micronutrient deficiencies in humans.

Treatment of Wilson's disease with zinc: III. Prevention of reaccumulation of hepatic copper

Twelve patients with Wilson's disease, most of whom had received intensive treatment with penicillamine, were given zinc therapy as their sole medication for copper control. Serial liver biopsies were performed during a 12- to 20-month follow-up period to determine whether hepatic copper reaccumulates during zinc therapy. Mean baseline liver copper concentration was 255 micrograms/gm dry weight, whereas the mean value after therapy was 239 micrograms. No patient demonstrated hepatic reaccumulation of copper during zinc therapy. Copper balance, 24-hour urinary copper excretion, and nonceruloplasmin plasma copper concentration all indicated good copper control during zinc therapy. Hepatic zinc concentration increased twofold to threefold over baseline values but no toxicity was seen. Hepatic zinc concentrations appeared to reach a plateau after 12 to 18 months of zinc therapy. We conclude that oral zinc as the sole maintenance therapy in patients with Wilson's disease prevents hepatic reaccumulation of copper.

Treatment of Wilson's disease with zinc. I. Oral zinc therapy regimens

The standard therapy for preventing copper accumulation in Wilson's disease, D-penicillamine, has been a life-saving drug, but it has many side effects and some patients are completely intolerant. We have been using oral zinc as another approach to the therapy for Wilson's disease, with copper balance studies as the key initial assessment of the adequacy of a given dose or regimen of zinc therapy. We earlier reported that an intensive regimen of zinc (zinc taken every 4 hr) was effective in controlling copper balance. We have now shown with balance studies that a simplified zinc therapy regimen of 50 mg zinc taken 3 times per day is effective in controlling copper balance. Preliminary work presented here with other simplified regimens also indicate their effectiveness. These studies increase the data base, in terms of copper balance, for zinc therapy of Wilson's disease, and expand the dose range and regimens of zinc which have been shown to control copper balance.

Treatment of Wilson's disease with zinc. II. Validation of oral 64copper with copper balance

The efficacy of zinc as a therapeutic agent to control copper balance in Wilson's disease patients has been previously documented with balance studies. In an attempt to develop a simpler and faster tool for evaluating the adequacy of zinc therapy, a technique that measures the uptake into blood of a small oral dose of 64copper was studied in conjunction with copper balance. The mean peak 64copper uptake into blood of nine Wilson's disease patients on D-penicillamine, trien, or no medication was 6.04 +/- 2.74%, comparable with normal controls. Seven patients on zinc therapy had a markedly and significantly reduced mean uptake of 0.79 +/- 1.05% after treatment. The data demonstrate that the prevention of copper uptake into blood in Wilson's disease patients by zinc therapy can be evaluated by 64copper uptake and that peak uptakes of less than 1% occur in patients with neutral or negative copper balance.

A collaborative, double-blind randomized study of cetiedil citrate in sickle cell crisis

We have recently completed a double-blind, placebo-controlled, noncrossover study, the goal of which was to determine whether cetiedil citrate (cetiedil) could affect the course of vaso-occlusive crises in sickle cell disease. Patients, who presented to the emergency room at least 4 but no more than 24 hours after the onset of a painful vasoocclusive crisis severe enough to require hospitalization, were considered candidates for the study. Each patient received either placebo or cetiedil at one of the following three dosages: 0.2, 0.3, or 0.4 mg/kg body weight. The assigned drug dosage was given as a 30 minute intravenous infusion every 8 hours for 4 consecutive days. A total of 67 patients was enrolled in the study. Cetiedil, at its highest dosage (0.4 mg/kg body weight), was found to be significantly superior to placebo both in reducing the number of painful sites present on all 4 treatment days and in shortening the total time in crisis. No serious adverse reactions were observed during the course of the study. We conclude that cetiedil, given at a dosage of 0.4 mg/kg body weight, is therapeutically advantageous for sickle cell crisis.

Corticosteroid For the Treatment of Porokeratosis of Mibelli

Intralesional triamcinolone and oral predtiisolone in low dosage with topical fl6ocinolone acetonide were tried in 10 cases of torokeratosis of mibehi. Moderate to good response was observed in 60% cases with flattening of the lesions, to, complete disappearance.

Zinc tolerance test in uremia. Effect of ferrous sulfate and aluminum hydroxide

The effects of ferrous sulfate and aluminum hydroxide on the oral zinc tolerance test after administration of 25 mg of elemental zinc as sulfate were studied in six hemodialysis patients and six normal controls. Fasting plasma zinc levels, the 2-hour plasma zinc peak, and the area under the plasma zinc curve were significantly lower in patients compared with values in controls (plasma zinc, 92 +/- 4 compared with 108 +/- 3 micrograms/dL, p less than 0.025; 2-hour plasma zinc peak, 159 +/- 8 compared with 228 +/- 17 micrograms/dL, p less than 0.025; and area under the curve, 193 +/- 41 compared with 316 +/- 39 micrograms h/dL, p less than 0.025). Ferrous sulfate (300 mg orally), when administered along with zinc sulfate, decreased the area under the curve significantly (in patients by 28%, in controls by 40%) in comparison with the results obtained when zinc sulfate was given alone. When 30 mL of aluminum hydroxide was administered orally with zinc sulfate, the area under the curve decreased by 60% in controls and 75% in patients (p less than 0.005). These results confirm the presence of diminished zinc absorption in patients with renal failure and show that ferrous sulfate and aluminum hydroxide, which worsen this defect, also impair zinc absorption in normal subjects.

Lymphocyte subpopulation abnormalities in sickle cell anemia: a distinctive pattern from that of AIDS

In this study, we evaluated lymphocyte subpopulations in 23 adults with SCA. When compared to controls, SCA patients had higher lymphocyte counts with normal numbers of T101+ cells (T-lymphocytes) and T4+ cells. T8+ cells were significantly increased in SCA patients in comparison to controls (1684 +/- 243 vs 980 +/- 367, p less than .001). This increment was largely dependent on a T101-, T8+ cell population. The SCA patients as a group had significantly decreased T4/T8 ratio (p less than .0001). The SCA patients with history of blood transfusions had higher T4+ cells numbers and higher T4/T8 ratio, but no other significant differences from nontransfused patients were noted. Our results are different from those reported for nontransfused children with SCA who showed normal T4/T8 ratio. Thus, a distinct pattern of abnormalities is seen in the lymphocyte subpopulations of adult SCA patients, unrelated to their exposure to blood transfusions.

Impaired IgM antibody responses to an influenza virus vaccine in adults with sickle cell anemia

Type-specific IgM and IgG antibody responses to a polyvalent influenza vaccine were evaluated in 16 adults with sickle cell anemia, with the use of an enzyme-linked immunosorbent assay. When compared to healthy controls, 8 out of the 16 patients had decreased or undetectable postvaccination anti-influenza IgM antibody levels. These patients were found to have significantly lower serum IgM levels and nondetectable splenic tissue (by 99Tc scans), as compared to those with normal IgM responses. Impaired IgM antibody primary immune responses may play a role in the pathogenesis of infectious complications seen in adult patients with sickle cell anemia.

Effect of zinc supplementation on hyperprolactinaemia in uraemic men

Zinc and prolactin levels were measured in 32 male haemodialysis patients; 12 were receiving 50 mg zinc per day as zinc acetate and 20 were not. Zinc-treated patients had significantly higher plasma zinc levels (134 +/- 10 micrograms/dl v 88 +/- 2 micrograms/dl) and lower serum prolactin levels (11 +/- 4 ng/ml v 29 +/- 7 ng/ml) than untreated patients. Plasma zinc and serum prolactin were inversely related in zinc-treated and untreated patients (r = -0.79, p less than 0.001).

Clinical and biochemical manifestation zinc deficiency in human subjects

During the past two decades, essentiality of zinc for man has been established. Deficiency of zinc in man attributable to nutritional factors and several diseased states has been recognized. High phytate content of cereal proteins decreases availability of zinc, thus the prevalence of zinc deficiency is likely to be high in the population subsisting on cereal proteins mainly. Zinc deficiency has been noted to occur in patients with malabsorption syndrome, chronic renal disease, cirrhosis of the liver, sickle cell disease, AE, and other chronically debilitating diseases. Growth retardation, male hypogonadism, skin changes, poor appetite, mental lethargy and delayed wound healing are some of the manifestations of chronically zinc-deficient human subjects. In severely zinc-deficient patients, dermatological manifestations, diarrhea, alopecia, mental disturbances and intercurrent infections predominate. If untreated, the condition becomes fatal. Zinc deficiency affects testicular functions adversely in man and animals. This effect of zinc is at the end-organ level. It appears that zinc is essential for spermatogenesis. Zinc is involved in many biochemical functions. Several zinc metalloenzymes have been recognized in the past decade. Zinc is required for each step of cell cycle in microorganisms and is essential for DNA synthesis. The effect of zinc on protein synthesis may be attributable to its vital role in nucleic acid metabolism. The activities of many zinc-dependent enzymes have been shown to be affected adversely in zinc-deficient tissues. Zinc atoms in some of the enzyme molecules participate in catalysis and also appear to be essential for maintenance of structure of apoenzymes. Zinc also plays a role in stabilization of biomembrane structure and polynucleotide confirmation.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical, endocrinological and biochemical effects of zinc deficiency

The essentiality of zinc for humans was recognized in the early 1960s. The causes of zinc deficiency include malnutrition, alcoholism, malabsorption, extensive burns, chronic debilitating disorders, chronic renal disease, certain diuretics, the use of chelating agents such as penicillamine for Wilson's disease, and genetic disorders such as acrodermatitis enteropathica and sickle cell disease. The requirement of zinc is increased in pregnancy and during the growing age period. The clinical manifestations in severe cases of zinc deficiency included bullous-pustular dermatitis, alopecia, diarrhoea, emotional disorder, weight loss, intercurrent infections, hypogonadism in males and it is fatal if untreated. A moderate deficiency of zinc is characterized by growth retardation and delayed puberty in adolescents, hypogonadism in males, rough skin, poor appetite, mental lethargy, delayed wound healing, taste abnormalities and abnormal dark adaptation. In mild cases of zinc deficiency in human subjects, we have observed oligospermia, slight weight loss and hyperammonaemia. Zinc is a growth factor. As a result of its deficiency, growth is affected adversely in many animal species and in man. Inasmuch as zinc is needed for protein and DNA synthesis and cell division, it is believed that the growth effect of zinc is related to its effect on protein synthesis. Testicular functions are affected adversely as a result of zinc deficiency in both humans and experimental animals. This effect of zinc is at the end organ level and the hypothalamic--pituitary axis is intact in zinc-deficient subjects. Inasmuch as zinc is intimately involved in a cell division, its deficiency may adversely affect testicular size and thus its function. In mice, the incidence of degenerate oocytes, and hypohaploidy and hyperhaploidy in metaphase II oocytes were increased due to zinc deficiency. Zinc at physiological concentrations reduced prolactin secretion from the pituitary in vitro and it has been suggested that this trace element may have a role in the in vivo regulation of prolactin release. Thymopoietin, a hormone needed for T-cell maturation, has also been shown to be zinc dependent. It is clear that zinc may have several roles in biochemical and hormonal functions of various endocrine organs. Future research in this area is very much needed.

Clinical manifestations of zinc deficiency

The essentiality of zinc for humans was recognized in the early 1960s. The causes of zinc deficiency include malnutrition, alcoholism, malabsorption, extensive burns, chronic debilitating disorders, chronic renal diseases, following uses of certain drugs such as penicillamine for Wilson's disease and diuretics in some cases, and genetic disorders such as acrodermatitis enteropathica and sickle cell disease. In pregnancy and during periods of growth the requirement of zinc is increased. The clinical manifestations in severe cases of zinc deficiency include bullous-pustular dermatitis, alopecia, diarrhea, emotional disorder, weight loss, intercurrent infections, hypogonadism in males; it is fatal if unrecognized and untreated. A moderate deficiency of zinc is characterized by growth retardation and delayed puberty in adolescents, hypogonadism in males, rough skin, poor appetite, mental lethargy, delayed wound healing, taste abnormalities, and abnormal dark adaptation. In mild cases of zinc deficiency in human subjects, we have observed oligospermia, slight weight loss, and hyperammonemia. Zinc is a growth factor. Its deficiency adversely affects growth in many animal species and humans. Inasmuch as zinc is needed for protein and DNA synthesis and for cell division, it is believed that the growth effect of zinc is related to its effect on protein synthesis. Whether or not zinc is required for the metabolism of somatomedin needs to be investigated in the future. Testicular functions are affected adversely as a result of zinc deficiency in both humans and experimental animals. This effect of zinc is at the end organ level; the hypothalamic-pituitary axis is intact in zinc-deficient subjects. Inasmuch as zinc is intimately involved in cell division, its deficiency may adversely affect testicular size and thus affect its functions. Zinc is required for the functions of several enzymes and whether or not it has an enzymatic role in steroidogenesis is not known at present. Thymopoeitin, a hormone needed for T-cell maturation, has also been shown to be zinc dependent. Zinc deficiency affects T-cell functions and chemotaxis adversely. Disorders of cell-mediated immune functions are commonly observed in patients with zinc deficiency. Zinc is beneficial for wound healing in zinc-deficient subjects. In certain zinc-deficient subjects, abnormal taste and abnormal dark adaptation have been noted to reverse with zinc supplementation.

Laboratory diagnosis of zinc deficiency

Zinc status in human subjects is assessed by measurement of zinc in plasma, erythrocytes, neutrophils, lymphocytes, and hair. Available data indicate that zinc in neutrophils and the assay of activity of alkaline phosphatase in neutrophils may be the best tools for the diagnosis of zinc deficiency. Measurement of zinc in the plasma is simple and readily available in many laboratories. Plasma zinc is useful provided the plasma is unhemolyzed and conditions, such as infections, acute stress, myocardial infarction and intravascular hemolysis, are ruled out. Inasmuch as hair and erythrocytes turn over slowly, their zinc levels do not reflect recent changes with respect to zinc status. Other useful parameters for assessment of zinc status include metabolic balance studies, urinary zinc excretion. Cu:Zn ratio, zinc tolerance test, and measurement of activities of zinc-dependent enzymes in suitable biological samples.