Oral Zinc Tolerance Test Research Articles

Clinical application of an oral zinc tolerance test.

Clinical application of an oral zinc tolerance test.

Lack of acute zinc effect on thyrotropin-releasing hormone–stimulated thyroid-stimulating hormone secretion during oral zinc tolerance test in healthy men

It is known that zinc interacts with thyroid hormones, altering plasma thyroid-stimulating hormones (TSH), triiodothyronine (T 3), and tetraiodothyronine (T 4) in rats and humans. To investigate whether zinc affects thyrotropin-releasing hormone (TRH)–stimulated TSH, 5 healthy men were tested at 8:00 am after an overnight fast. Elemental zinc (37.5 mg, as heptahydrated zinc sulfate) was administered orally, and TRH (200 μg) was administered intravenously for 1 minute. Blood samples were collected from an antecubital vein at −30, 0, 30, 60, 90, 150, 210, 240, 270, and 300 minutes. Serum zinc remained constant throughout the control period. However, serum zinc was significantly elevated after oral zinc administration in the experimental group ( P < .05). Plasma TSH levels increased after TRH injection in the control and in the experimental group, although not significantly when comparing both groups. Moreover, no significant areas under the curves and no correlation between serum zinc and plasma TSH levels were detected in both groups studied. This is the first study that showed the relationship between TRH-stimulated TSH secretion during oral zinc tolerance test in healthy men. These results suggest that a single oral dose of zinc did not change TSH secretion after TRH injection. Furthermore, acute increases in blood TRH and TSH did not alter serum zinc levels.

Zinc pharmacokinetics in insulin-dependent diabetes mellitus patients after oral zinc tolerance test

Zinc is an essential micronutrient that is directly involved in the physiology of insulin, and zinc metabolism could play a role in the pathogenesis of diabetes mellitus and its complications. On the other hand, low zinc absorption and hyperzincuria in diabetic animals and humans have indicated that diabetics are more susceptible to zinc deficiency. This study was designed to compare zinc metabolism in ten insulin-dependent diabetic patients with ten healthy controls, using an oral zinc tolerance test. Pharmacokinetic parameters were performed to study intestinal zinc absorption and urinary zinc excretion. Absorption of zinc was extensive during the first two hours after administration of a single oral dose of 25 mg Zn ++. The area under the serum zinc curve (AUC) and maximum concentration of zinc (C max) did not differ in both control and experimental groups, p < 0.05. In addition, absorption rate constant (K a), elimination rate constant (K el), absorption half-life (T 1/2a), elimination half-life (T 1/2el), and time of maximum concentration (T max) were not significantly different between the diabetic patients and controls ( p > 0.05). All these kinetic parameters suggest that there is no malabsorption of zinc in diabetic patients. Conversely, zinc clearance/creatinine clearance ratio (CZn ++/Ccr ratio) in diabetic patients differed significantly in comparison to controls, p < 0.05, indicating renal dysfunction in these patients. We conclude that a single oral dose of zinc can be used to investigate zinc absorption and zinc clearance, and that diabetic patients have a specific normal gastrointestinal function and renal dysfunction in terms of zinc clearance.

Effects of zinc deficiency/zinc supplementation on ammonia metabolism in patients with decompensated liver cirrhosis.

Hepatic encephalopathy is one of the major complications in decompensated liver cirrhosis. The current study was conducted to clarify the mechanisms of zinc deficiency in liver cirrhosis and its involvement in hepatic encephalopathy via ammonia metabolism. Ten patients each with compensated or decompensated liver cirrhosis and 11 healthy volunteers were enrolled in the study. Serum zinc levels and its daily urinary excretion were measured, an oral zinc-tolerance test was performed to examine zinc malabsorption, and the effects of diuretics on zinc excretion and of zinc supplementation on ammonia metabolism in the skeletal muscle were studied. The mean serum zinc levels in patients with decompensated liver cirrhosis were found to be significantly lower than the levels in controls and patients with compensated liver cirrhosis. The serum zinc levels were inversely correlated with blood ammonia in the fasting state. In the oral zinc-tolerance test, the percent increase in serum zinc levels 120 and 180 min after ingestion was less in cirrhotic patients than in controls. A diuretic administration resulted in a significant reduction in serum zinc levels. An increased uptake of ammonia by and an increased release of glutamine from leg skeletal muscle after oral supplementation of zinc sulfate were evident. Taken together, zinc deficiency in decompensated cirrhotic patients appears to be due to low absorption and to high urinary excretion, for which excessive diuretic administration is, in part, responsible, and zinc supplementation might play an important role in the prevention of hepatic encephalopathy by activating glutamine synthetase.

Oral zinc tolerance test in pregnant women

Zinc (Zn) is essential for fetal growth and development, and Zn requirement is increased during pregnancy. The purpose of this study was to determine whether intestinal Zn absorption is increased during pregnancy in order to maintain Zn homeostasis. Oral Zn tolerance test (ZnTT) was performed on 25 healthy pregnant women and 7 healthy non-pregnant female volunteers after the administration of 22.5 mg elemental Zn as sulphate following an overnight fast at a single oral dose. Although the mean baseline plasma Zn level was lower in pregnant women than the controls (P < 0.05), there was no statistically significant difference in Zn absorption as determined by the 2nd- and 3rd-hour plasma Zn levels. The relative dose responses also did not show a significant difference between the pregnant and the control groups. Furthermore, different trimesters and the nutritional status did not have a significant impact on Zn absorption. The results suggest that the lack of a compensatory increase in intestinal Zn absorption in spite of the low Zn status in pregnancy may suggest the intestinal factor as a contributary factor in poor bioavailability. J. Trace Elem. Exp. Med. 14:17–23, 2001. © 2001 Wiley-Liss, Inc.

Oral zinc tolerance test in pregnant women

Zinc (Zn) is essential for fetal growth and development, and Zn requirement is increased during pregnancy. The purpose of this study was to determine whether intestinal Zn absorption is increased during pregnancy in order to maintain Zn homeostasis. Oral Zn tolerance test (ZnTT) was performed on 25 healthy pregnant women and 7 healthy non-pregnant female volunteers after the administration of 22.5 mg elemental Zn as sulphate following an overnight fast at a single oral dose. Although the mean baseline plasma Zn level was lower in pregnant women than the controls (P < 0.05), there was no statistically significant difference in Zn absorption as determined by the 2nd- and 3rd-hour plasma Zn levels. The relative dose responses also did not show a significant difference between the pregnant and the control groups. Furthermore, different trimesters and the nutritional status did not have a significant impact on Zn absorption. The results suggest that the lack of a compensatory increase in intestinal Zn absorption in spite of the low Zn status in pregnancy may suggest the intestinal factor as a contributary factor in poor bioavailability. J. Trace Elem. Exp. Med. 14:17–23, 2001. © 2001 Wiley-Liss, Inc.

Effect of 1,2‐Dimethyl‐3‐Hydroxypyridin‐4‐One (L1) on zinc absorption

The aim of the study was to determine the effect of L1 on zinc absorption in healthy individuals. Ten healthy volunteer individuals were included. Oral zinc tolerance test was performed first with 120 mg ZnSO4·7H2O (22.5 mg elementary zinc) and then with zinc sulfate and deferiprone (L1) at a dose of 500 mg. Plasma and urine zinc concentrations were assessed by an atomic absorption spectrophotomer. When zinc profile values during the OZTT were compared, there was only a significant increase during the 3rd hour (147 ± 6.5 μg/dl vs. 166.4 ± 13.8 μg/dl) in the zinc sulfate + L1 trial. However AUC4 values for both tests were 2.623 ± 0.193 and 2.874 ± 0.247, respectively. The difference was not significant (P > .05). Our data revealed that L1 does not have a negative effect on zinc absorption. So, we concluded that L1 and zinc can be given together orally. J. Trace Elem. Exp. Med. 11:5–9, 1998. © 1998 Wiley-Liss, Inc.

Effect of 1,2-Dimethyl-3-Hydroxypyridin-4-One (L1) on zinc absorption

The aim of the study was to determine the effect of L1 on zinc absorption in healthy individuals. Ten healthy volunteer individuals were included. Oral zinc tolerance test was performed first with 120 mg ZnSO4·7H2O (22.5 mg elementary zinc) and then with zinc sulfate and deferiprone (L1) at a dose of 500 mg. Plasma and urine zinc concentrations were assessed by an atomic absorption spectrophotomer. When zinc profile values during the OZTT were compared, there was only a significant increase during the 3rd hour (147 ± 6.5 μg/dl vs. 166.4 ± 13.8 μg/dl) in the zinc sulfate + L1 trial. However AUC4 values for both tests were 2.623 ± 0.193 and 2.874 ± 0.247, respectively. The difference was not significant (P > .05). Our data revealed that L1 does not have a negative effect on zinc absorption. So, we concluded that L1 and zinc can be given together orally. J. Trace Elem. Exp. Med. 11:5–9, 1998. © 1998 Wiley-Liss, Inc.

Pregnancy outcome of mothers with defective oral zinc tolerance test

Pregnancy outcome of four previously reported women with impaired zinc absorption was determined. These women were supplemented with zinc sulphate for 6 months. Their plasma Zn levels prior to conception were within normal levels. Of the four deliveries, all newborns were normal; only one had closed spina bifida. Our data are further evidence for a possible role of zinc metabolism, at least in some mothers with previous neural tube defects (NTD) babies. J. Trace Elem. Exp. Med. 10:153–154, 1997. © 1997 Wiley-Liss, Inc.

The application of an oral zinc tolerance test to assess zinc absorption from three different dietary sources in the dog

Zinc (Zn) is a key nutrient for dogs, playing an important role in many metabolic functions. It has been estimated that 91% of the minimum maintenance requirement for Zn is needed to support hair growth. Coat condition is perceived as being important by pet owners and is thus of fundamental concern when evaluating the adequacy of a diet for dogs.Zn absorption has been shown to vary as a function of the amount and source of the Zn in the diet and as a function of the presence of elevated calcium and / or phytate levels in the diet.It has been suggested that when dietary Zn is supplied in the form of a chelate with amino acids, rather than from inorganic sources, a greater proportion of Zn is absorbed an is thus available to the animal. Further, the undesirable effects that dietary antagonists, such as calcium, exert on Zn absorption may be negated

The application of an oral zinc tolerance test to assess zinc absorption from three different dietary sources in the dog

Zinc (Zn) is a key nutrient for dogs, playing an important role in many metabolic functions. It has been estimated that 91% of the minimum maintenance requirement for Zn is needed to support hair growth. Coat condition is perceived as being important by pet owners and is thus of fundamental concern when evaluating the adequacy of a diet for dogs.Zn absorption has been shown to vary as a function of the amount and source of the Zn in the diet and as a function of the presence of elevated calcium and / or phytate levels in the diet.It has been suggested that when dietary Zn is supplied in the form of a chelate with amino acids, rather than from inorganic sources, a greater proportion of Zn is absorbed an is thus available to the animal. Further, the undesirable effects that dietary antagonists, such as calcium, exert on Zn absorption may be negated

A standardized oral zinc tolerance test for assessment of zinc absorption in dogs.

Three oral zinc tolerance tests using increasing doses of elemental zinc (0.5, 0.75 and 1.0 mg/kg) given as zinc sulphate (ZnSO4.7H2O) were carried out in eight normal beagles. The zinc tolerance curves obtained were similar to those described in man, with the peak plasma zinc concentration occurring 2 h after dosing. There was a considerable variation between individual animals in the peak plasma zinc concentration achieved with each dose. This would appear to limit the value of a zinc tolerance test in assessing the efficiency of zinc absorption in individuals, although it may be of value in making comparisons between groups of dogs.

Oral plasma zinc tolerance test in patients with protein energy malnutrition.

Zinc absorption was measured in 37 children with malnutrition using the oral zinc tolerance test (22.5 mg elementary zinc) and the results compared with those of a group of healthy control subjects. The increase in plasma zinc was significantly lower in patients with marasmic kwashiorkor than in the control group. The zinc tolerance test was, however, normal in marasmic patients. We conclude that zinc deficiency occurs in some types of protein energy malnutrition, and that malabsorption may aggravate zinc deficiency. It is reasonable to give higher doses of zinc than are usually recommended during oral zinc supplementation in patients with protein energy malnutrition.

Zinc plasma levels after oral zinc tolerance test in nonalcoholic cirrhosis.

Zinc absorption was examined in 25 nonalcoholic cirrhotic patients using the oral zinc tolerance test and comparing results to a healthy control group. With 22.5 mg elementary zinc, the increase in plasma zinc was significantly lower in the cirrhotic patients than in the control group with P less than 0.01 in the first and second hours and P less than 0.05 in the fourth hour. The zinc malabsorption may result from an abnormal small intestinal mucosa. Indeed small intestinal biopsies in all patients showed partial shortening and prominent distension of villi and intense stromal edema with inflammatory cell infiltration of the lamina propria. However, it is not clear whether these intestinal changes are due to zinc deficiency or to portal hypertension. Thus zinc malabsorption appears to contribute to zinc deficiency in nonalcoholic cirrhotics and seems to result, in part, from pathological changes in the mucosa.

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.

The increase in zincaemia provoked by starvation does not influence the intestinal absorption of zinc

Serum zinc, measured in obese patients undergoing two weeks of therapeutic starvation (0 kcal, water ad libitum) increased significantly during the starvation period (+ 48% at day 10) and returned to prestarvation values after refeeding with a 500 kcal diet. Intestinal absorption of zinc was investigated by an oral zinc tolerance test (with 75 mg of zinc acetate) on the second and the tenth day of starvation. No significant differences were observed between the first and the second test. In our experimental conditions 10 days of starvation failed to induce a loss of zinc exceeding 0.75% of the total body stores. It is concluded that the concentration of zinc in blood per se does not regulate intestinal absorption in the absence of a significant change in zinc requirements.

Low Erythrocyte Zinc Content in Acquired Aphasia With Convulsive Disorder (Landau-Kleffner Syndrome)

Abnormal zinc metabolism in a 6-year-old male patient with Landau-Kleffner syndrome (acquired aphasia and convulsive disorder) is the subject of our report. We describe a significant decrease of erythrocyte and plasma zinc levels in the patient as compared with normal. Red blood cell zinc content is normally 38.5 +/- 2.7 micrograms/g hemoglobin v 16.5 micrograms/g hemoglobin found in the patient. Plasma zinc level is 94.6 +/- 10.4 micrograms/dL in normal in comparison with 50.4 micrograms/dL in the patient. Normal oral zinc tolerance test performed on the patient precludes altered zinc absorption or increased urinary loss. The possible connection between abnormal zinc metabolism and the pathophysiology of Landau-Kleffner syndrome is discussed.

Does the oral zinc tolerance test measure zinc absorption?

Increases in plasma zinc concentration were compared with radiozinc absorption after oral test doses. Ten healthy, fasting subjects were each given 385 mumol zinc chloride (25 mg Zn) labelled with 0.5 muCi 65ZnCl2 and a non-absorbed marker, 51CrCl3, dissolved in 100 ml of water; another 10 persons were given 354 mumol zinc chloride and 125 g of minced turkey containing 31 mumol zinc also labelled with 65Zn and 51Cr. Measurements were made of plasma zinc concentration at hourly intervals for 5 hours, radiozinc absorption by stool counting of unabsorbed radioactivity 12-36 hours later, and radiozinc retention by whole body counting at 7 days. The mean percentage of radiozinc absorbed and retained in the body from the two test meals was found to be identical (42%). In contrast the increased area under the plasma zinc curve up to 5 hours after the turkey meal, 28 +/- 9 mumol/L (mean +/- SD) was significantly less than that for zinc chloride alone, 47 +/- 15 mumol/L, p less than 0.005. Despite this difference, a good correlation was found between the area under the plasma zinc curve and 65Zn absorption in individual subjects after each meal. The discrepancy between the results of zinc absorption derived from the plasma zinc curve and 65Zn absorption for the liquid and solid test meals was most likely explained by binding of zinc to food and delayed gastric emptying of the solid meal. With a test meal of turkey meat at least this dampened the plasma appearance of zinc but did not affect its overall absorption.