John H. Livesey

Effect of anticoagulants and storage temperatures on stability of plasma and serum hormones

OBJECTIVES To determine the effect of different anticoagulants and storage conditions on the stability of hormones in plasma and serum. DESIGN AND METHODS Human blood samples were collected from volunteers into EDTA, lithium heparin, sodium fluoride/potassium oxalate, or tubes without anticoagulant, plasma and serum left at -20 degrees C, 4 degrees C or 30 degrees C for 24 and 120 hours then assayed for ACTH, aldosterone, alpha-subunit, AVP, CRH, C-peptide, estradiol, FSH, glucagon, GH, IGF-1, IGFBP-3, insulin, leptin, LH, PPP, PTH, prolactin and VIP, or at room temperature for 0 to 72 hours (BNP, NT-BNP)(n = 6 per condition). RESULTS The anticoagulant altered the measured concentrations for 9 hormones when compared to EDTA. All hormones except ACTH were stable for > 120 hours in EDTA or fluoride at 4 degrees C, but only 13 hormones were stable in all anticoagulants. At 30 degrees C, 8 hormones were stable for > 120 hours in EDTA, and 3 hormones in all anticoagulants. BNP and NT-BNP were stable for < 24 hours when stored in EDTA or heparin at room temperature. DISCUSSION Storage of samples in EDTA plasma at 4 degrees C is suitable for most hormones (except ACTH) for up to 120 hours.

Effect of Vitamin D3 Supplementation on Upper Respiratory Tract Infections in Healthy Adults: The VIDARIS Randomized Controlled Trial

CONTEXT Observational studies have reported an inverse association between serum 25-hydroxyvitamin D (25-OHD) levels and incidence of upper respiratory tract infections (URTIs). However, results of clinical trials of vitamin D supplementation have been inconclusive. OBJECTIVE To determine the effect of vitamin D supplementation on incidence and severity of URTIs in healthy adults. DESIGN, SETTING, AND PARTICIPANTS Randomized, double-blind, placebo-controlled trial conducted among 322 healthy adults between February 2010 and November 2011 in Christchurch, New Zealand. INTERVENTION Participants were randomly assigned to receive an initial dose of 200,000 IU oral vitamin D3, then 200,000 IU 1 month later, then 100,000 IU monthly (n = 161), or placebo administered in an identical dosing regimen (n = 161), for a total of 18 months. MAIN OUTCOME MEASURES The primary end point was number of URTI episodes. Secondary end points were duration of URTI episodes, severity of URTI episodes, and number of days of missed work due to URTI episodes. RESULTS The mean baseline 25-OHD level of participants was 29 (SD, 9) ng/mL. Vitamin D supplementation resulted in an increase in serum 25-OHD levels that was maintained at greater than 48 ng/mL throughout the study. There were 593 URTI episodes in the vitamin D group and 611 in the placebo group, with no statistically significant differences in the number of URTIs per participant (mean, 3.7 per person in the vitamin D group and 3.8 per person in the placebo group; risk ratio, 0.97; 95% CI, 0.85-1.11), number of days of missed work as a result of URTIs (mean, 0.76 days in each group; risk ratio, 1.03; 95% CI, 0.81-1.30), duration of symptoms per episode (mean, 12 days in each group; risk ratio, 0.96; 95% CI, 0.73-1.25), or severity of URTI episodes. These findings remained unchanged when the analysis was repeated by season and by baseline 25-OHD levels. CONCLUSION In this trial, monthly administration of 100,000 IU of vitamin D did not reduce the incidence or severity of URTIs in healthy adults. TRIAL REGISTRATION anzctr.org.au Identifier: ACTRN12609000486224.

FGF23 Elevation and Hypophosphatemia after Intravenous Iron Polymaltose: A Prospective Study

CONTEXT Parenteral iron administration has been associated with hypophosphatemia. Fibroblast growth factor 23 (FGF23) has a physiological role in phosphate homeostasis via suppression of 25-hydroxyvitamin D [25(OH)D] activation and promotion of phosphaturia. We recently reported a case of iron-induced hypophosphatemic osteomalacia associated with marked FGF23 elevation. OBJECTIVE Our objective was to prospectively investigate the effect of parenteral iron polymaltose on phosphate homeostasis and to determine whether any observed change was related to alterations in circulating FGF23. DESIGN, SETTING, AND PARTICIPANTS Eight medical outpatients prescribed iv iron polymaltose were recruited. Plasma phosphate, 25(OH)D, 1,25-dihydroxyvitamin D [1,25(OH)(2)D], PTH, FGF23, and urinary tubular reabsorption of phosphate were measured prior to iron administration and then weekly for a minimum of 3 wk. RESULTS Plasma phosphate fell from 3.4 +/- 0.6 mg/dl at baseline to 1.8 +/- 0.6 mg/dl at wk 1 (P < 0.0001) associated with a fall in percentage tubular reabsorption of phosphate (90 +/- 4.8 to 68 +/- 13; P < 0.001) and 1,25(OH)(2)D (54 +/- 25 to 9 +/- 8 pg/ml; P < 0.001). These indices remained significantly suppressed at wk 2 and 3. 25(OH)D levels were unchanged. FGF23 increased significantly from 43.5 pg/ml at baseline to 177 pg/ml at wk 1 (P < 0.001) with levels correlating with both serum phosphate (R = -0.74; P <0.05) and 1,25(OH)(2)D (R = -0.71; P < 0.05). CONCLUSION Parenteral iron suppresses renal tubular phosphate reabsorption and 1alpha-hydroxylation of vitamin D resulting in hypophosphatemia. Our data suggest that this is mediated by an increase in FGF23.

Adaptation of the hypothalamopituitary adrenal axis to chronic exercise stress in humans.

Repeated acute or chronic exposure to a particular stress results in adaptation whereby the hypothalamopituitary adrenal (HPS) axis becomes less responsive to subsequent or continued exposure to that particular stress. To investigate the adaptive changes that occur in the HPA axis in response to chronic stress in humans, we studied the effect of chronic exercise stress on basal activity of the HPA axis in six highly trained male ultramarathon athletes and six healthy male controls matched for body mass index. After 3-5 of abstention from intense physical activity, the subjects were admitted to a metabolic study ward at 1600 h. Peripheral blood was sampled initially at 0300 h, at 20-min intervals from 0400 to 0900 h, hourly from 0900 to 1200 h, and then every 2 h from 1200 to 1600 h. A 24-h urine collection was completed during the admission. Peripheral blood adrenocorticotropic hormone (ACTH) was measured by radioimmunoassay. Plasma and urinary cortisol were measured by enzyme-linked immunoassay. Plasma and injury cortisol were measured by enzyme-linked immunosorbent assay (ELISA). Plasma ACTH and cortisol levels showed the expected diurnal change in athletes and control subjects (P = 0.00001). However, the early morning ACTH and cortisol surge occurred earlier in the athletes than in the controls (P = 0.026). Plasma ACTH levels were significantly higher in the athletes than in the control subjects (P = 0.0026). There was, however, no significant overall difference in plasma cortisol levels between the athletes and the control subjects, and urinary excretion of free cortisol was similar in the two groups. These data show that intense physical training leads to adaptive changes in basal HPA function, including a phase shift and increased pituitary in basal HPA function, including a phase shift and increased pituitary ACTH secretion, but also blunting of the adrenal cortisol response.

Low-dose growth hormone replacement lowers plasma leptin and fat stores without affecting body mass index in adults with growth hormone deficiency.

OBJECTIVE The ob gene product, leptin, is considered to be a marker of adipose tissue mass and a possible homeostatic regulator of body mass. Our objective was to examine the effect of GH replacement on adipose tissue stores and leptin in adult hypopituitarism.

The plasma ACTH, AVP, CRH and catecholamine responses to conventional and laparoscopic cholecystectomy

OBJECTIVES We compared the responses of the stress hormones, Cortisol, ACTH, vasopressin (AVP), corticotrophin releasing hormone (CRH) and catecholamines to elective conventional and laparoscopic cholecystectomy.

Hormone stability in human whole blood

OBJECTIVE To determine whether significant changes in the plasma concentrations of 17 hormones occur when human whole blood is held at 4 or 24 degrees C for up to 24 h before separation of the plasma fraction. DESIGN AND METHODS Blood samples (EDTA) from healthy human volunteers were held at 4 degrees C or 24 degrees C for 0.5, 6 or 24 h before separation. Plasma concentrations of ACTH, aldosterone, gonadotrophin alpha-subunits, AVP, C-peptide, estradiol, FSH, GH, glucagon, IGF-1, IGFBP3, insulin, leptin, LH, prolactin, PTH and VIP were measured and the results compared to baseline values. Nonlinear regression was used to test for a significant mean rate of change. The time interval for median concentrations to change by 10% was determined. RESULTS Significant changes were observed for ACTH (decrease at 18.6 hr, 4 degrees C; 17.5 hr, 24 degrees C); AVP (increase at 2.6 h, 24 degrees C); insulin (decrease at 16.8 hr, 4 degrees C; 16.9 hr, 24 degrees C) and VIP (increase at 18.6 h, 24 degrees C). No changes were detected for the remaining analytes.B CONCLUSIONS: The measurement of some hormones is compromised by a delay in plasma separation from normal human blood. While many hormones appear stable in normal whole blood, we recommend that processing occurs without delay.

PLASMA CORTICOTROPHIN‐RELEASING FACTOR AND VASOPRESSIN RESPONSES TO HYPOGLYCAEMIA IN NORMAL MAN

The plasma Cortisol, ACTH, AVP and corticotrophin‐releasing factor (CRF) responses to insulin‐induced hypoglycaemia were investigated in six normal men using a controlled, randomized, cross‐over design. Hormonal concentrations were determined following insulin or saline injection. The maximum Cortisol response was seen at 90 min while plasma ACTH, AVP and CRF concentrations peaked at 45 min following insulin injection. The responses of the insulin‐treated and control groups were compared by assessing the incremental response from baseline (pre‐injection) to peak hormone levels. A significant increase was observed for each hormone following insulin injection. The mean of the incremental responses between 30 and 120 min in each subject was also statistically greater for each hormone in the insulin‐treated group when compared with the control group. These results are consistent with the hypothesis that AVP and CRF are both physiological mediators of ACTH secretion induced by a hypoglycaemic stress.

Plasma corticotrophin releasing hormone, vasopressin, ACTH and Cortisol responses to acute myocardial infarction

OBJECTIVES We assessed the magnitude and duration of the response of hypothalamic‐pituitary‐adrenal hormones to the stress of myocardial infarction, in the presence and absence of angiotensin converting enzyme inhibitors. In particular, we wished to analyse the interrelationships between peripheral plasma levels of corticotrophin releasing hormone (CRH), vasopressin (AVP) and adrenocorticotrophin (ACTH), and also between ACTH and Cortisol, during a prolonged medical stress.

Effect of Naloxone on the Hormone Response to crf in Normal man

Ovine corticotropin releasing factor (CRF) was administered to six normal men and the plasma ACTH and cortisol responses compared with those following the same dose of CRF (200 micrograms) plus the opiate receptor blocker naloxone (20mg). The addition of naloxone was associated with a significant increase in plasma ACTH, cortisol and aldosterone responses. No change was observed in peripheral plasma levels of epinephrine, norepinephrine, arginine vasopressin, angiotensin II or renin activity in response to CRF plus naloxone. It is concluded that endogenous opioid peptides may inhibit the ACTH response to CRF. However the addition of naloxone does not increase the ACTH response to CRF sufficiently to constitute a useful test of pituitary function.