Diurnal and nocturnal variations of the serum iron in normal subjects

A prospective cohort examination of haematological parameters in relation to cancer death and incidence: the Busselton Health Study

BACKGROUND

Cancer risk is associated with serum iron levels. The aim of this study was to evaluate whether haematological parameters reflect serum iron levels and may also be associated with cancer risk.

METHODS

We studied 1564 men and 1769 women who were enrolled in the Busselton Health Study, Western Australia. Haematological parameters evaluated included haemoglobin (Hb), mean cell volume (MCV), mean cell haemoglobin (MCH) and mean cell haemoglobin concentration (MCHC) and red cell distribution width (RCDW). Statistical analyses included t-tests for quantitative variables, chi-square tests for categorical variables and Cox proportional hazards regression modelling for cancer incidence and death.

RESULTS

There was marginal evidence of an association between MCV (as a continuous variable) and non-skin cancer incidence in women (HR 1.15, 95% CI 1.013, 1.302; p = 0.030) but the hazard ratio was attenuated to non-significance after adjustment for serum ferritin (SF), iron and transferrin saturation (TS) (HR 1.11, 95% CI 0.972, 1.264; p = 0.126). There was strong evidence of an association between MCHC and prostate cancer incidence in men; the estimated hazard ratio for an increase of one SD (0.5) in MCHC was 1.27 (95% CI 1.064, 1.507; p = 0.008). These results remained significant after further adjustment for SF and iron; the estimated hazard ratio for an increase of one SD (0.5) in MCHC was 1.25 (p = 0.014, 95% CI 1.05 to 1.48).

CONCLUSIONS

The MCHC and MCV were associated with cancer incidence in a Western Australian population, although only MCHC remained associated with prostate cancer after adjusting with serum iron and TS (circulating iron) and SF (storage iron). Haematological parameters are thus of limited utility in population profiling for future cancer risk.

Effect of iron supplementation during lactation on maternal iron status and oxidative stress: A randomized controlled trial

We examined the effect of iron-containing prenatal vitamin-mineral supplements taken postpartum on biomarkers of iron status and oxidative stress. Lactating women (n = 114) were randomly assigned to consume daily one iron-free prenatal vitamin-mineral supplement plus either 27 mg of iron or placebo for approximately 3.5 months. The placebo group took the tablets between meals, while those given iron took the tablets either with (Fe-W) or between meals (Fe-B). Blood and urine samples were collected before and after the supplementation period to analyze hemoglobin (Hb), ferritin, hepcidin, transferrin saturation (TfSat), total plasma iron, and biomarkers of oxidative stress (isoprostane and 8-hydroxy-2-deoxyguanosine (8-OHdG)) and inflammation (C-reactive protein (CRP) and alpha-1-acid glycoprotein (AGP)). There was a trend toward a greater change in Hb among women in the Fe-B group compared to placebo (+2.5 vs. -3.7 g/L, respectively, p = 0.063). When the iron groups were combined, there was a greater change in Hb (+1.4 g/L) compared to placebo (p = 0.010). There were trends toward greater changes in TfSat (p = 0.087) and total plasma iron (p = 0.065) in the iron groups compared to placebo, yet no significant differences between the three groups in change in hepcidin (p = 0.291), isoprostane (p = 0.319), or 8-OHdG (p = 0.659), nor in change in ferritin among those with elevated CRP at baseline (60% of women; p = 0.946); among those without elevated CRP (40% of women), ferritin increased more in the iron groups compared to placebo (p = 0.001). Iron consumption during lactation moderately increased iron status, particularly among women without elevated CRP, and increased Hb, but did not significantly increase oxidative stress.

Association of iron indices and type 2 diabetes: a meta-analysis of observational studies

The literature on the role of body iron status in the development of type 2 diabetes (T2D) in humans is inconsistent. We aimed to assess the association between iron indices and T2D by a meta-analysis of previously published studies. A systematic literature search was conducted in PubMed and EMBASE. Observational studies on the association of ferritin (when controlled for age and sex), transferrin saturation, soluble transferrin receptor and transferrin with T2D were included. Pooled association estimates were calculated using a random effects model. Forty-six eligible studies were identified. The pooled multivariable adjusted relative risks of T2D in the highest versus lowest quartile of ferritin levels were significantly elevated in both cross-sectional as well as prospective studies and after restriction to inflammation-adjusted studies [overall: 1.67 (95% CI 1.41-1.99)]. The mean difference indicated 43.54 ng/mL (95% CI 28.14-58.94) higher ferritin levels in type 2 diabetic individuals. The relative risk for a transferrin saturation ≥ 50% was 1.59 (95% CI 1.28-1.97), the mean difference was -1.92% [95% CI -2.99-(-0.85)]. Study-specific results of soluble transferrin receptor and transferrin levels were extremely heterogeneous. Ferritin and clinically elevated transferrin saturation were strongly associated with an increased risk of T2D, overall and in prospective studies. Ferritin was also significantly associated after multivariable adjustment including inflammation. Thus, the current evidence hints at a causal effect; however, publication bias and unmeasured confounding cannot be excluded.

Inverse correlation between serum interleukin-6 and iron levels among Japanese adults: a cross-sectional study

BACKGROUND

Interleukin-6 (IL-6) is a multifunctional cytokine that is produced by many different cell types, and plays an important role in the regulation of inflammation, immune responses, the acute-phase response, and hematopoiesis. Previous laboratory and clinical studies have shown that IL-6 causes a significant decrease in serum iron levels. Therefore, we conducted an epidemiological study to examine the association between serum IL-6 and iron levels.

METHODS

In total, 280 Japanese individuals aged 20-78 years were enrolled when they visited a clinic located in an urban area for Helicobacter pylori (H. pylori) infection tests and subsequent eradication; 65.3% were infected with H. pylori. Subjects with gastric cancer, idiopathic thrombocytopenia, or IL-6 > 10 pg/mL were excluded from the study. Serum iron and IL-6 levels were measured using the 2-nitroso-5-(N-propyl-3-sulfopropylamino) phenol method and chemiluminescence enzyme immunoassay, respectively.

RESULTS

Geometric mean iron and IL-6 levels were 111.5 μg/dL and 1.77 pg/mL, respectively, for men, and 89.4 μg/dL and 1.55 pg/mL, respectively, for women. The logarithm of serum iron levels was negatively correlated with the logarithm of IL-6 levels in men (r = -0.19, p = 0.047), but not in women (r = -0.035, p = 0.65). Regression analysis, adjusted for sex, age, and H. pylori infection status, showed that the logarithm of serum iron levels was significantly associated with a decreased logarithm of IL-6 levels (β = -0.053, p = 0.041). The odds ratio for low serum iron levels adjusted for sex, age, and H. pylori infection status was 7.88 (95% CI 1.29-48.06) in those with an IL-6 level > 4 pg/mL.

CONCLUSION

Lower serum iron levels are significantly associated with higher serum IL-6 levels among Japanese adults.

Circulating human hepcidin-25 concentrations display a diurnal rhythm, increase with prolonged fasting, and are reduced by growth hormone administration

BACKGROUND

Hepcidin-25 reduces iron absorption by binding to the intestinal iron transporter ferroportin and causing its degradation. Currently, little is known about the basal regulation of circulating hepcidin-25. In addition, although erythropoietin administration has been reported to decrease the circulating hepcidin concentration, information is limited regarding how other stimulators of erythropoiesis, such as growth hormone (GH), might alter hepcidin-25 concentrations.

METHODS

We used a sensitive and specific hepcidin-25 dual-monoclonal antibody sandwich immunoassay to measure hepcidin-25 in healthy human volunteers at various time points throughout the day and during 3 days of fasting and subsequent refeeding. We also measured hepcidin-25 concentrations in healthy volunteers after GH administration.

RESULTS

In healthy individuals, hepcidin-25 concentrations displayed a diurnal variation, with concentrations being lowest in the early morning and steadily increasing throughout the day before declining during the evening hours, a pattern that was not influenced by food intake. Prolonged fasting produced statistically significant increases in hepcidin-25 concentrations. Refeeding reversed this process, and GH administration markedly decreased hepcidin-25 concentrations.

CONCLUSIONS

Our results indicate that in humans, hepcidin-25 exhibits diurnal changes that can be altered by prolonged fasting, which increases hepcidin-25 concentrations approximately 3-fold after 3 days of fasting, possibly owing to a suppression of erythropoiesis that may occur during the fasting state to preserve tissue iron concentrations. In contrast, GH administration decreased hepcidin-25 concentrations by approximately 65%, presumably by stimulating erythropoiesis. These results indicate that circulating hepcidin-25 concentrations display much more dynamic and rapid variation than might have been anticipated previously.

Circadian rhythm in serum iron levels

This study was aimed at assessing the circadian rhythm of serum iron levels in Chinese healthy subjects. The project was conducted in 19 healthy, Chinese male subjects following a 4-day diet equilibration. Blood samples were collected on day 5 at 0800, 1000, 1200, 1400, 1600, 1800, 2000, and 2400 hours to determine endogenous serum iron concentrations. Iron concentrations were determined using an inductively coupled plasma mass spectrometry. Iron concentration was decreased from morning to afternoon. The minimum value of iron level was 1,987 μg/L at 2000 hours while the maximum was 2,229 μg/L at 1000 hours, and 2,278 μg/L at 1400 hours, respectively, the amplitude was 291 μg/L. This study indicates that when assessing the bioequivalence of iron formulations, baseline levels of iron (obtained before dosing) should not be subtracted simply from the amount obtained on the drug dosing day to yield the net effect of iron formulation administration. More valid methods to optimize the design of such bioequivalence studies should be taken into consideration.

Diurnal variation of hematology parameters in healthy young males: the Bispebjerg study of diurnal variations

PURPOSE

To evaluate the influence of time of day on the circulating concentrations of 21 hematology parameters.

MATERIALS AND METHODS

Venous blood samples were obtained under standardized circumstances from 24 healthy young men every third hour through 24 hours, nine time points in total. At each time point, the level of melatonin, iron, transferrin, transferrin saturation, ferritin, cobalamin, folate, red blood cells and white blood cells was measured. The data were analysed by rhythmometric statistical methods. The biological variations were calculated.

RESULTS

Significant oscillation of melatonin (p < 0.0001) with an amplitude (amp) of 19.84 pg/ml and a peak level at 03:34 h confirmed the normal 24-hour rhythms of the participants. Erythrocytes (p < 0.0001, amp = 0.15 × 10(12)/L), hemoglobin (p < 0.0001, amp = 0.29 mmol/L), hematocrit (p < 0.0001, amp = 0.01), iron (p < 0.0001, amp = 4.00μmol/L), transferrin (p = 0.03, amp = 1.41μmol/L), transferrin saturation (p < 0.0001, amp = 6.37%) and folate (p < 0.0001, amp = 1.55nmol/L) oscillated significantly, with gradually falling mean levels through the day to nadir around midnight. Leukocyte count (p < 0.0001, amp = 0.78 × 10(9)/L), neutrophils (p = 0.001, 0.31 × 10(9)/L), eosinophils (p < 0.0001, amp = 0.04 × 10(9)/L), monocytes (p = 0.0009, amp = 0.06 × 10(9)/L), lymphocytes (p < 0.0001, amp = 0.49 × 10(9)/L) oscillated significantly with gradually increasing mean levels through the day peaking at midnight. Iron, leukocytes and hemoglobin had the highest 24 hour oscillations in proportion to the reference intervals of the parameters for healthy young men.

CONCLUSIONS

Biochemical screenings are biased by diurnal variations, which must be considered when blood concentrations of these parameters are interpreted in the clinical setting.

Fortification iron as ferrous sulfate plus ascorbic acid is more rapidly absorbed than as sodium iron EDTA but neither increases serum nontransferrin-bound iron in women

The absorption profile of iron fortificants may be a determinant of their ability to generate nontransferrin-bound iron (NTBI) and, thus, their potential safety. Ferrous iron may be absorbed more rapidly than chelated ferric iron, but differences at the fortification level cannot be distinguished with nonisotopically labeled serum iron curves. Using stable isotope appearance curves (SIAC) in serum, we measured iron absorption profiles from FeSO(4) with ascorbic acid (AA) and from NaFeEDTA, as well as the serum hepcidin and NTBI response following the meals. Healthy women (n = 16) were given 6 mg oral iron as labeled FeSO(4) and NaFeEDTA with a maize porridge using a crossover design. SIAC, NTBI, and serum hepcidin were measured over 8 h after the meal. Iron from FeSO(4) plus AA was more rapidly absorbed, resulting in a 35% greater relative AUC during the first 2 h than for NaFeEDTA (P < 0.001). Median (95% CI) fractional iron absorption from the FeSO(4)- and NaFeEDTA-fortified meals was 15.2% (11.0-19.5) and 6.0% (5.0-9.2), respectively (P < 0.001). In response to the FeSO(4)-fortified meal, there was an ~60% increase in median serum hepcidin (P < 0.05) but no significant change in NTBI. There was no significant change in serum hepcidin or NTBI after the NaFeEDTA-fortified meal. SIAC are a useful new tool to compare iron absorption profiles from different iron compounds in fortified foods. Even with the use of a very well absorbed ferrous iron compound, iron fortification in this population does not increase NTBI, suggesting a low risk for adverse health consequences.

Serum iron increase as a measure of iron absorption - studies on the correlation with total absorption

The correlation between the magnitude of the increase of serum iron after an oral dose of iron and the total absorption of iron was studied in 51 healthy subjects and 10 patients with iron deficiency anaemia. 59Fe-labelled solutions of ferrous sulphate (25-100 mg iron) were administered to the fasting subjects. The serum iron concentration was followed for 4-6 hours and the absorption was measured in a whole-body counter. Good correlation was found between the maximal increase of serum iron and the total amount of iron absorbed after a dose of iron given as a solution. The serum iron method may be used for comparisons of the absorbability of different doses of iron by performing cross-over studies in groups of subjects. However, it was found that in an individual subject the serum iron method could not be used to determine the amount of iron absorbed from an oral dose of iron.

Immunoassay for human serum hepcidin

We developed and validated the first serum enzyme-linked immunosorbent assay for hepcidin, the principal iron-regulatory hormone that has been very difficult to measure. In healthy volunteers, the 5% to 95% range of hepcidin concentrations was 29 to 254 ng/mL in men (n = 65) and 17 to 286 ng/mL in women (n = 49), with median concentrations 112 versus 65 (P < .001). The lower limit of detection was 5 ng/mL. Serum hepcidin concentrations in 24 healthy subjects correlated well with their urinary hepcidin (r = 0.82). Serum hepcidin appropriately correlated with serum ferritin (r = 0.63), reflecting the regulation of both proteins by iron stores. Healthy volunteers showed a diurnal increase of serum hepcidin at noon and 8 pm compared with 8 am, and a transient rise of serum hepcidin in response to iron ingestion. Expected alterations in hepcidin levels were observed in a variety of clinical conditions associated with iron disturbances. Serum hepcidin concentrations were undetectable or low in patients with iron deficiency anemia (ferritin < 10 ng/mL), iron-depleted HFE hemochromatosis, and juvenile hemochromatosis. Serum hepcidin concentrations were high in patients with inflammation (C-reactive protein > 10 mg/dL), multiple myeloma, or chronic kidney disease. The new serum hepcidin enzyme-linked immunosorbent assay yields accurate and reproducible measurements that appropriately reflect physiologic, pathologic, and genetic influences, and is informative about the etiology of iron disorders.

Diurnal variation of serum iron, iron-binding capacity, transferrin saturation, and ferritin levels

Serum iron levels vary throughout the day. Morning levels are generally assumed to be higher than afternoon or evening levels. We studied whether our practice of restricting serum iron collections to the morning was necessary. Serum iron, iron-binding capacity, transferrin saturation, and ferritin levels were determined on blood specimens obtained from 20 healthy adult volunteers at 8 AM, noon, and 4 PM (day 1) and 8 AM (day 2). Although statistically significant differences among mean values for the collection times were observed for iron, iron-binding capacity, and (log) ferritin, no consistent diurnal variation was seen. Morning iron levels were higher than afternoon levels for only half of the subjects. Between-day variation for all 4 analytes was similar to within-day variation. We conclude that the practice of restricting iron specimen collections to a specific time of day does not improve the reliability of the test result.

Iron status of the free-living, elderly Framingham Heart Study cohort: an iron-replete population with a high prevalence of elevated iron stores

BACKGROUND

Although iron deficiency occurs commonly in vulnerable groups of women of reproductive age, infants, and children, less is known about the iron nutriture of the elderly.

OBJECTIVE

Our objective was to evaluate the iron status of a noninstitutionalized, elderly US population, with a particular focus on 2 concerns unique to the elderly: 1) potential confounding effects of chronic disease on iron measures and 2) increased occurrence of elevated iron stores.

DESIGN

Multiple iron measures, including serum ferritin (SF), transferrin saturation, mean cell volume, and hemoglobin, were used to evaluate the prevalence of iron deficiency (ID), iron deficiency anemia (IDA), and other measures of iron nutriture in 1016 elderly white Americans aged 67-96 y from the Framingham Heart Study. "Diseased" subjects were defined as those with possible pathologically altered iron measures due to inflammation, infection, elevated liver enzymes, hereditary hemochromatosis, or cancer. The effect of altered iron status on various prevalence estimates was assessed.

RESULTS

The elderly subjects had a low prevalence of ID (2.7%), IDA (1.2%), and depleted iron stores (3%; SF < 12 microg/L). In contrast, 12.9% had elevated iron stores (SF > 300 microg/L in men and SF > 200 microg/L in women), of which only 1% was attributable to chronic disease. The prevalence of ID, IDA, and depleted iron stores was unaffected by the presence of chronic disease.

CONCLUSIONS

The Framingham Heart Study cohort is an iron-replete elderly population with a high prevalence of elevated iron stores in contrast with a low prevalence of iron deficiency, with insignificant effects of chronic disease on these iron status estimates. The likely liability in iron nutriture in free-living, elderly white Americans eating a Western diet is high iron stores, not iron deficiency.

Pediatric reference ranges for creatine kinase, CKMB, Troponin I, iron, and cortisol

OBJECTIVES

To determine the pediatric reference ranges for iron, cortisol, CK, CKMB, and troponin I.

METHODS

Iron and CK were measured on the Vitros analyzer (Johnson and Johnson) while CKMB, troponin I, and cortisol were measured on the Immuno I (Bayer Corp.). Pediatric reference ranges were determined on hospitalized patients using the Hoffmann approach.

RESULTS

Pediatric reference ranges were obtained for iron (AM and PM) and cortisol (AM and PM). Ranges were also obtained for CKMB, troponin I, and total CK.

CONCLUSION

This work represents an expansion in our knowledge base on pediatric reference ranges. For iron, the 97.5th percentiles were significantly higher in the PM than in the AM. The diurnal fluctuation in 97.5th percentiles for cortisol was only 10-20%. Pediatric reference ranges for CKMB were not previously available and are important especially in the first year of life. The elevated Troponin I is found in the first year of life also represents new data.

Practice guideline development task force of the College of American Pathologists. Hereditary hemochromatosis

Hereditary hemochromatosis is an autosomal recessive disorder, the gene for which occurs in approximately 10% of Americans, most of whom are unaffected heterozygotes. Approximately 5/1000 white Americans are homozygous and at risk of developing severe and potentially lethal hemochromatosis. The disorder affects numerous organ systems, but the most common symptoms are fatigue, palpitations, joint pains, and impotence; the most common signs are those that relate to hypothalamic, cardiac, hepatic or pancreatic dysfunction, including poor cold tolerance, impotence in males, amenorrhea in females, cardiac arrhythmias, dyspnea, edema, hepatosplenomegaly, spider telangiectases, ascites, deformity, swelling or limitation of motion of joints, weight loss, hyperpigmentation. Characteristic abnormalities of laboratory tests include elevated serum iron concentration, high transferrin saturation, elevated serum ferritin concentration, elevated serum transaminases, hyperglycemia and low values for thyroid-stimulating hormone (TSH) and gonadotropins. Death may be the result of cardiac arrhythmia, congestive heart failure, liver failure or liver cancer. Since many of these complications cannot be reversed once they have developed, early diagnosis and treatment are essential. In view of the high prevalence in the American population (prevalence varies with ethnic background), the low cost of diagnosis and treatment, the efficacy of treatment if begun early, and, on the other hand, high costs and low success rate of late diagnosis and treatment, systematic screening for hemochromatosis is warranted for all persons over the age of 20 years. The initial screening should be by measurement of serum iron concentration and transferrin saturation. The practice guideline provides a diagnostic algorithm for cases in which the serum transferrin saturation is 60% or greater. It also provides guidelines for clinical management.

Relationship between iron status and chronic akathisia in an in-patient population with chronic schizophrenia

Iron status and akathisia were assessed in 105 long-stay in-patients who fulfilled DSM-III-R criteria for schizophrenia, all but three of whom were receiving antipsychotic medication. Chronic akathisia was diagnosed in 23% and pseudoakathisia in 20%. No significant correlation was found between serum iron concentration and the severity of akathisia. There was no significant difference in serum iron concentration between patients with chronic akathisia and those without. However, serum iron and percentage saturation were significantly raised in patients with pseudoakathisia compared with patients with chronic akathisia, and tended to be higher than in patients with akathisia. These findings do not support an association between low serum iron and chronic akathisia.

Influence of food intake on the 24-hr variations of plasma iron concentration in the rabbit

Circadian variations in plasma iron levels were first reported in humans in 1937. Influences of the sleeping pattern and of plasma cortisol and adrenaline levels on these variations as well as the reproducibility of the phenomenon itself are discussed controversially in the literature. The influence of food intake, however, was not considered in most of the studies and is therefore subject of this investigation. Circadian plasma iron and plasma transferrin variations were determined in rabbits and compared under free access to food and under starvation (caecotrophy was not prevented). Population-mean-cosinor analysis of circadian plasma iron concentrations showed similar variations in the fed and starved condition (mesor: 116.6 micrograms/dl vs 118.1 micrograms/dl, acrophase 0752 hr vs 0728) except for a significant increase of the circadian amplitude under free access to food (30.9 micrograms/dl vs 22.3 micrograms/dl, P less than 0.05). There was no variation in plasma transferrin, which shows that 24 hr variations in plasma iron are not caused by modulation of plasma transferrin. These findings demonstrate a circadian rhythm for plasma iron, the amplitude of which is increased by food intake.

Circadian rhythms in the aged: a review

After a review of the fundamental concepts on chronobiology, the importance of circadian rhythms in the aged was examined on the basis of the data obtained in animals and humans, including personal observations on over 40 blood constituents. During ageing there are significant modifications of circadian rhythms, with frequent diminution of amplitude and a shift of acrophase. The biological, clinical and therapeutic implications of these findings are discussed.

Effect of oral iron supplementation during pregnancy on maternal and fetal iron status

The known increased need for iron during pregnancy appears to be met only in part by increased iron absorption and amenorrhea. Considerable demands are made on maternal iron stores and, since many women lack sufficient storage iron, pregnancy may be expected to cause iron deficiency. This may lead to anemia in pregnancy and post partum and could also have a bearing on the iron status of the fetus and the neonate. Based on these considerations, prophylactic supplementation of dietary iron is advocated but remains a disputed issue. In the present controlled, prospective and longitudinal study changes in hematologic status, and in particular in iron stores, during pregnancy were investigated in 44 healthy Caucasian women with uncomplicated pregnancies and deliveries. They were randomly assigned to a study group (n = 21) receiving oral iron supplements from the 16th week of amenorrhea until 6 weeks post partum, and a control group (n = 23) without iron supplementation. Maternal concentrations of hemoglobin, serum iron, serum transferrin and serum ferritin were determined at 16, 28 and 36 weeks of amenorrhea, at delivery, and 6 and 12 weeks post partum. The same variables were determined in cord blood. Iron supplementation appeared to prevent the physiologic fall in hemoglobin and serum iron concentrations which occurred in the control group, but had little influence on the observed rise in transferrin concentrations. Ferritin levels in serum, which are known to reflect mobilisable iron stores, fell to 30% of the initial values in the control group and to 70% in the study group. Six and 12 weeks post partum ferritin levels were still low in the nonsupplemented group (Tab. I).(ABSTRACT TRUNCATED AT 250 WORDS)

The laboratory evaluation of microcytic red blood cells

Microcytic red blood cell states are common clinical problems in both adult and pediatric age groups. The recent widespread availability of electronic blood cell counters for performing routine blood counts has increased the detection of microcytic red blood cells. Physicians must workup both symptomatic and asymptomatic patients with microcytic red blood cells before they can initiate proper therapy and/or counseling. The purpose of this review is threefold: (1) to discuss the causes of microcytic red blood cells in terms of disorders of decreased heme production vs. disorders of decreased globin production, (2) to review the clinical laboratory tests useful in differentiating microcytic red blood cell states, and (3) to present a practical approach for the laboratory workup of microcytic red blood cells.

[The plasma 59Fe clearance curve in man. An evaluation of methods of measurement and analysis]

Studies of 59Fe clearance from the plasma are used for obtaining a quantitative measure of erythropoiesis. However, there are many difficulties associated with a good definition and a valid analysis of the plasma 59Fe clearance curve. The low plasma activity, plasma iron variation, and traces of haemolysis are factors which make the measurement of the curve difficult. All these problems were examined in the present work. Liquid scintillation counting allows a more accurate assay of plasma 59Fe activity than conventional gamma counting. Plasma iron fluctuations may affect tracer kinetics but adjustment of plasma activity for plasma iron variation (expressing 59Fe activity per unit mass of iron) does not appear a satisfactory procedure for overcoming this difficulty. The removal of haemoglobin from plasma samples is a necessary procedure to avoid contamination by [59Fe] haemoglobin. Fitting three exponentials to the plasma 59Fe clearance curve does not yield satisfactory results in some cases. A better prediction of the clearance curve in most cases can be obtained by means of a more refined mathematical model.

Serum ferritin and iron stores during pregnancy

The iron status of two groups of pregnant women was investigated. One group did not receive iron (group B), the other erceived 100 mg iron/day (group A). 1. In all individuals concentrations of hemoglobin, serum iron, transferrin and serum ferritin were determined at regular intervals from the third month until delivery and at 3 months after delivery. The same determinations were performed in cord blood. 2. Changes in iron status appeared to be less in individuals with iron supplement than in those without iron supplement. A fall in Hb, serum iron and serum ferritin is observed in all individuals. 3. Three months after delivery the Hb concentration has generally returned to the normal female value, but the serum ferritin concentration is still very low. 4. The fetus does not discriminate as to the iron status of the mother. In both groups (A and B) cord blood values appeard to be not significantly different.

Variation of serum iron concentration in young healthy men: Within-day and day-to-day changes

1. Serum iron concentration values were determined on a group of 11 healthy young men on blood specimens which were drawn at various hours of the day: 800 h, 1100 h, and 1400 h; on each of four separate days. 2. using a three-way ANOVA (analysis of variance) model, we determined the diurnal variation both for the group as a whole (main hour effect) and for the individual subjects (subject-hour and subject-day-hour interactions). 3. the total combined within-day variation as expressed in coefficients of variation was 12.9% with the peak value seen at 1400 h. 4. on a separate study, blood specimens were obtained at 1100 h on five separate days during a two week period on the same volunteers. 5. using a two-way ANOVA model (subject and day) the day-to-day coefficient of variation was found to be 26.6% for the group. In both cases (within-day and day-to-day) the biological variation was considerably greater than the analytic variation.