Discordance between mass spectrometry and immunometric IGF-1 assay in pituitary disease: a prospective study.

PURPOSE: Measuring IGF-1, a biomarker for GH activity, is critical to evaluating disordered hypothalamic-pituitary GH axis. Inconsistent IGF-1 measurements among different immunoassays are well documented. We switched from Immulite 2000 immunoassay to narrow-mass-extraction, high-resolution liquid chromatography mass-spectrometry (LC-MS) compliant with recent consensus recommendations on assay standardization. Comparability of these two assays in patients with pituitary disease in a clinical practice setting is not known. We sought to compare IGF-1 levels on Immulite 2000 and LC-MS in samples from naïve and treated patients with secretory and non-secretory pituitary masses. METHODS: We prospectively collected serum samples from 101 patients treated at the Cedars-Sinai Pituitary Center between February 2012 and March 2014. We intentionally recruited more patients with acromegaly or GH deficiency to ensure a clinically representative cohort. Samples were classified as in or out of the respective reference ranges. Bland-Altman analysis was used to assess agreement between assays. RESULTS: Twenty-four percent of samples were classified differently as below, in, or above range. Agreement between the assays was poor overall, with a significant bias for immunoassay reporting higher values than LC-MS. This pattern was also observed in patients with acromegaly and those with ≥ 2 pituitary hormone deficiencies. CONCLUSIONS: IGF-1 results may differ after switching from an older immunoassay to a consensus-compliant assay such as LC-MS. Clinicians should consider the potential impact of assay switching before altering treatment due to discrepant results, particularly in patients monitored over time, such as those with acromegaly and GH deficiency.

Quantitative insulin analysis using liquid chromatography-tandem mass spectrometry in a high-throughput clinical laboratory.

BACKGROUND: Circulating insulin concentrations reflect the amount of endogenous insulin produced by the pancreas and can be monitored to check for insulin resistance. Insulin is commonly measured using immunochemiluminometric assays (ICMA). Unfortunately, differing crossreactivities of the various ICMA antibodies have led to variability in assay results. In contrast, liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based approaches can provide a highly specific alternative to immunoassays. METHODS: Insulin was extracted from patient serum and reduced to liberate the insulin B chain. Subsequent resolution of the peptide was achieved by LC coupled to triple-quadrupole MS. Selected-reaction monitoring of B-chain transitions was used for quantification. Recombinant human insulin was used as a calibrator and was compared against the National Institute for Biological Standards and Control (NIBSC) reference standard. Bovine insulin and a stable isotopic-labeled ((13)C/(15)N) human insulin B chain were used and compared as internal standards. RESULTS: The LC-MS/MS assay described herein has been validated according to CLIA guidelines with a limit of detection of 1.8 µIU/mL (10.8 pmol/L) and a limit of quantitation of 3 µIU/mL (18.0 pmol/L). A correlation between the LC-MS/MS assay and a US Food and Drug Administration-approved ICMA was completed for patient samples and the resulting Deming regression revealed good agreement. A reference interval for the assay was established. CONCLUSIONS: A simple, high-throughput, quantitative LC-MS/MS insulin assay traceable to the NIBSC standard has been successfully developed and validated.

Bile acid concentration reference ranges in a pregnant Latina population.

OBJECTIVE: The total bile acid (TBA) concentration criterion for diagnosing intrahepatic cholestasis of pregnancy varies in the published literature. The purpose of this study was to establish pregnancy-specific reference ranges for the TBA concentration among Latina women. STUDY DESIGN: Self-identified Latina women (n = 211) over 18 years of age with a singleton pregnancy were recruited and had random serum samples drawn during the second and third trimesters. The total and fractionated bile acid concentrations were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS), and reference ranges were calculated. Laboratory-provided general reference ranges from a general population of adult men and nonpregnant women were used for comparison. RESULTS: The TBA reference range for our Latina pregnant population (<8.5 µmol/L) was markedly lower than the laboratory-provided reference range (4.5 to 19.2 µmol/L). CONCLUSION: These data suggest that the upper TBA concentration reference range in our Latina pregnant population is 8.5 µmol/L, based on LC-MS/MS measurements.

Testosterone reference ranges in normally cycling healthy premenopausal women.

INTRODUCTION: At present, there are no well-accepted reference ranges for serum testosterone concentrations in women. AIM: The aim of this study was to determine the reference ranges for serum testosterone and sex hormone-binding globulin (SHBG) in premenopausal women with normal menstrual cycles. METHODS: We measured serum total, free, and bioavailable testosterone and SHBG concentrations in 161 healthy, normally cycling women (18-49 years). Morning blood samples were collected during follicular, mid-cycle, and luteal phases of the menstrual cycle and analyzed using validated methods. Mean, median, and weighted average hormone levels across menstrual cycle phases as well as percentiles for a typical 30-year-old woman were determined. MAIN OUTCOME MEASURES: Age-related serum levels of total, free, and bioavailable testosterone and SHBG levels in normally cycling premenopausal women. RESULTS: Serum testosterone concentrations exhibited an age-related decline, whereas SHBG remained relatively stable across studied age ranges. Reference ranges for total, free, and bioavailable testosterone and SHBG were established using 5th and 95th percentiles. The estimated 5th and 95th percentiles for a 30-year-old woman were: testosterone, 15-46 ng/dL (520-1595 pmol/L); free testosterone, 1.2-6.4 pg/mL (4.16-22.2 pmol/L); calculated free testosterone, 1.3-5.6 pg/mL (4.5-19.4 pmol/L); bioavailable testosterone, 1.12-7.62 ng/dL (38.8-264.21 pmol/L); and SHBG 18-86 nmol/L. The variations of hormones and SHBG across menstrual cycle were consistent with previous literature. CONCLUSIONS: Reference ranges for free, total, and bioavailable testosterone and SHBG were established in premenopausal women using validated immunoassays and an adequate number of subjects consistent with recommendations by the National Committee for Clinical Laboratory Standards. The increase in testosterone in the mid-cycle period is relatively small compared with the overall variability, so these reference ranges can be applied irrespective of the day in the menstrual cycle the sample has been taken.

Plasma renin activity by LC-MS/MS: development of a prototypical clinical assay reveals a subpopulation of human plasma samples with substantial peptidase activity.

BACKGROUND: For management and treatment of secondary hypertension, plasma renin activity (PRA) assay is considered an essential diagnostic tool. We developed a liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based approach to PRA offering improvements in laboratory workflow and throughput. During development, we observed a substantial number of clinical samples that have strong degradation activity toward angiotensin (Ang) I during generation. A preliminary characterization of this degradation activity was performed, and we provide here a method by which this degradation can be monitored via the addition of an isotope-labeled degradation standard. METHODS: Automated online sample extraction coupled with HPLC was used to isolate Ang I and internal standard from plasma. The effluent from the analytical column was directed to a triple quadrupole MS operated in selected reaction monitoring mode, monitoring the a(5) and b(5) product ions from the [M+3H](+3) precursors. Routine analysis could be achieved with as little as 150 µL plasma. RESULTS: We identified both C-terminal and N-terminal degradation products of Ang I using isotope-labeled peptides as controls and substrates. In 2%-5% of patient samples, the degradation essentially eliminated any Ang I produced during generation. CONCLUSIONS: Our method requires reduced sample handling when compared with an RIA and eliminates the need for extended generation times for samples with low renin activity. Degradation of Ang I during generation appears to be a confounding variable in the interpretation of results from some clinical samples. Samples with profound degradation activity can be identified using a degradation standard that is added at the start of generation.

Ion mobility analysis of lipoprotein subfractions identifies three independent axes of cardiovascular risk.

OBJECTIVE: Whereas epidemiological studies show that levels of low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C) predict incident cardiovascular disease (CVD), there is limited evidence relating lipoprotein subfractions and composite measures of subfractions to risk for CVD in prospective cohort studies. METHODS AND RESULTS: We tested whether combinations of lipoprotein subfractions independently predict CVD in a prospective cohort of 4594 initially healthy men and women (the Malmö Diet and Cancer Study, mean follow-up 12.2 years, 377 incident cardiovascular events). Plasma lipoproteins and lipoprotein subfractions were measured at baseline with a novel high-resolution ion mobility technique. Principal component analysis (PCA) of subfraction concentrations identified 3 major independent (ie, zero correlation) components of CVD risk, one representing LDL-associated risk, a second representing HDL-associated protection, and the third representing a pattern of decreased large HDL, increased small/medium LDL, and increased triglycerides. The last corresponds to the previously described "atherogenic lipoprotein phenotype." Several genes that may underlie this phenotype-CETP, LIPC, GALNT2, MLXIPL, APOA1/A5, LPL-are suggested by SNPs associated with the combination of small/medium LDL and large HDL. CONCLUSIONS: PCA on lipoprotein subfractions yielded three independent components of CVD risk. Genetic analyses suggest these components represent independent mechanistic pathways for development of CVD.

Validation of hepascore, compared with simple indices of fibrosis, in patients with chronic hepatitis C virus infection in United States.

BACKGROUND & AIMS: Biomarkers are being developed as alternatives to liver biopsy for predicting liver fibrosis in patients with chronic hepatitis C. Hepascore uses noninvasive serum markers and has been validated in Australian and European populations for predicting different degrees of fibrosis. This study validated this test in a U.S. population. METHODS: Patients with chronic hepatitis C virus infection were assigned to training (n = 203) or validation (n = 188) sets. Liver fibrosis was staged according to the METAVIR scoring system. The Hepascore algorithm uses data on age, sex, as well as total bilirubin, gamma-glutamyl transferase, alpha2-macroglobulin, and hyaluronic acid levels. RESULTS: The ability of Hepascore to predict significant fibrosis (F2-4) as determined by the area under the receiver operating curve was similar in training (0.83) and validation sets (0.81) and was comparable to results seen in previous studies. A cutoff score of > or =0.55 was best for predicting significant fibrosis, with a sensitivity and specificity of 82% and 65% and positive and negative predictive values of 70% and 78%. When compared with 2 simple indices, FIB-4 (age, platelets, AST, and ALT) and APRI (AST/platelet ratio index), Hepascore performed better at excluding advanced fibrosis by using a low cutoff score but worse at predicting fibrosis by using a high cutoff score. An algorithm with Hepascore followed by FIB-4 or APRI spared 103 of 391 individuals a liver biopsy and missed advanced fibrosis in only 1 patient. CONCLUSIONS: Hepascore accurately predicted likelihood of developing fibrosis and could alleviate the need for liver biopsy in a subset of patients.

Vitamin D2 is as effective as vitamin D3 in maintaining circulating concentrations of 25-hydroxyvitamin D.

CONTEXT: Two reports suggested that vitamin D2 is less effective than vitamin D3 in maintaining vitamin D status. OBJECTIVE: Our objective was to determine whether vitamin D2 was less effective than vitamin D3 in maintaining serum 25-hydroxyvitamin D levels or increased the catabolism of 25-hydroxyvitamin D3. SUBJECTS AND DESIGN: This was a randomized, placebo-controlled, double-blinded study of healthy adults ages 18-84 yr who received placebo, 1000 IU vitamin D3, 1000 IU vitamin D2, or 500 IU vitamin D2 plus 500 IU vitamin D3 daily for 11 wk at the end of the winter. RESULTS: Sixty percent of the healthy adults were vitamin D deficient at the start of the study. The circulating levels of 25-hydroxyvitamin D (mean+/-sd) increased to the same extent in the groups that received 1000 IU daily as vitamin D2 (baseline 16.9+/-10.5 ng/ml; 11 wk 26.8+/-9.6 ng/ml), vitamin D3 (baseline 19.6+/-11.1 ng/ml; 11 wk 28.9+/-11.0 ng/ml), or a combination of 500 IU vitamin D2 and 500 IU vitamin D3 (baseline 20.2+/-10.4 ng/ml; 11 wk 28.4+/-7.7 ng/ml). The 25-hydroxyvitamin D3 levels did not change in the group that received 1000 IU vitamin D2 daily. The 1000 IU dose of vitamin D2 or vitamin D3 did not raise 25-hydroxyvitamin D levels in vitamin D-deficient subjects above 30 ng/ml. CONCLUSION: A 1000 IU dose of vitamin D2 daily was as effective as 1000 IU vitamin D3 in maintaining serum 25-hydroxyvitamin D levels and did not negatively influence serum 25-hydroxyvitamin D3 levels. Therefore, vitamin D2 is equally as effective as vitamin D3 in maintaining 25-hydroxyvitamin D status.

Direct determination of lipoprotein particle sizes and concentrations by ion mobility analysis.

BACKGROUND: Current methods for measuring the concentrations of lipoprotein particles and their distributions in particle subpopulations are not standardized. We describe here and validate a new gas-phase differential electrophoretic macromolecular mobility-based method (ion mobility, or IM) for direct quantification of lipoprotein particles, from small, dense HDL to large, buoyant, very-low-density lipoprotein (VLDL). METHODS: After an ultracentrifugation step to remove albumin, we determined the size and concentrations of lipoprotein particles in serum samples using IM. Scan time is 2 min and covers a particle range of 17.2-540.0 A. After scanning, data are pooled by totaling the particle number across a predetermined size range that corresponds to particular lipoprotein subclasses. IM results were correlated with those of standard methods for cholesterol and apolipoprotein analysis. RESULTS: Intra- and interassay coefficients of variation for LDL particle size were <1.0%. The intra- and interassay variation for LDL and HDL particle subfraction measurements was <20%. IM-measured non-HDL correlated well with apolipoprotein B (r = 0.92). CONCLUSIONS: The IM method provides accurate, reproducible, direct determination of size and concentration for a broad range of lipoprotein particles. Use of this methodology in studies of patients with cardiovascular disease and other pathologic states will permit testing of its clinical utility for risk assessment and management of these conditions.

Correlation of Insulin-Like Growth Factor-I and -II Concentrations at Birth Measured by Mass Spectrometry and Growth from Birth to Two Months.

BACKGROUND: Immunoassays used to measure insulin-like growth factor (IGF)-I and -II concentrations are susceptible to interference from IGF-binding proteins. The aim of this study was to investigate the association of IGF-I and -II concentrations at birth with neonatal anthropometry using a liquid chromatography/mass spectrometry (LCMS) assay. METHODS: LCMS was used to measure IGF-I and -II concentrations in umbilical cord blood of term, healthy infants enrolled in the Cork BASELINE Birth Cohort Study. Weight, length, and occipitofrontal head circumference (OFC) were measured at birth and 2 months. RESULTS: Cord blood IGF-I and -II concentrations were measured in 1,100 infants. Mean (SD) IGF-I and -II concentrations were 52.5 (23.9) ng/mL and 424.3 (98.2) ng/mL, respectively. IGF-I and -II concentrations at birth were associated (p < 0.05) with weight (R2 = 0.19, R2 = 0.01), length (R2 = 0.07, R2 = 0.004), and OFC (R2 = 0.03, R2 = 0.04) at birth. Low IGF-I concentrations at birth were associated with increases in weight (p < 0.001) and OFC (p < 0.01) Z-scores in the first 2 months. CONCLUSION: Using an LCMS assay, we have shown that anthropometric parameters at birth are associated with IGF-I and weakly with IGF-II concentrations. This indicates that, at the time of birth, IGF-I is the more important growth factor for regulating infant growth.

A cross-sectional study of bone turnover markers in healthy premenopausal women.

BACKGROUND: Biochemical markers of bone turnover (BTMs) provide useful information in the diagnosis and management of metabolic bone diseases. Currently, there exist few published reference ranges for bone markers in healthy premenopausal women using the newer, automated assays of bone turnover. This cross-sectional study of healthy premenopausal women was performed to determine reference ranges for four different markers of bone turnover and to compare reference ranges in users and non-users of oral contraceptives (OCs). METHODS: Urinary N-telopeptide of type 1 collagen (NTX) was determined from fasting second morning-void urine of healthy premenopausal women. In addition, fasting serum was collected for determination of C-telopeptide of type I collagen (CTX), bone-specific alkaline phosphatase (bone ALP), and N-terminal propeptide of type 1 procollagen (PINP). Subjects underwent central dual energy X-ray absorptiometry and completed a questionnaire regarding medical history and activities known to affect bone health. RESULTS: Serum and urine samples were collected from 237 healthy premenopausal women (119 OC users and 118 non-users) between the ages of 28 and 45 years. The mean age of subjects was 37 years, with a mean bone mineral density T-score of -0.1 at the lumbar spine and 0.0 at the total hip. Logarithmic transformation produced normal distributions for all markers but NTX. Mid-95% ranges for each marker were generally consistent with those reported by manufacturers. For each BTM examined, values were skewed toward the lower end of the range. Median NTX levels for OC users and non-users were 16.0 and 29.0 nmol/mmol creatinine, respectively. The mid-95% ranges for NTX in OC users and non-users were 3-60 and 4-64 nmol/mmol creatinine, respectively. Median levels of CTX, bone ALP, and PINP were also lower in OC users than non-users. The mean level of each BTM was significantly lower in OC users than non-users (P<0.01), whereas reference ranges (geometric mean+/-2 SD) were somewhat similar for the two groups. CONCLUSION: Values obtained from this well-characterized population provide reference ranges for BTMs in healthy premenopausal women. Median and mean BTM levels for OC users were consistently lower compared with non-users; thus, separate reference ranges are required for these two groups of premenopausal women. The relevance of premenopausal reference ranges for postmenopausal women remains uncertain.

Total and free cortisol levels during 1 µg, 25 µg, and 250 µg cosyntropin stimulation tests compared to insulin tolerance test: results of a randomized, prospective, pilot study.

PURPOSE: The appropriate cosyntropin dose during cosyntropin stimulation tests remains uncertain. We conducted a prospective, randomized pilot study to compare 1 µg IV low dose cosyntropin test, 25 µg IM medium dose cosyntropin test, and 250 µg IM standard dose cosyntropin test to evaluate secondary adrenal insufficiency. Insulin tolerance test was used as the gold standard. METHOD: The study included patients with hypothalamic/pituitary disease (n = 10) with at least one pituitary axis deficiency other than ACTH deficiency and controls (n = 12). All tests were done in random order. Sensitivity and specificity were calculated for total cortisol and serum free cortisol cut-off levels during cosyntropin stimulation tests. RESULTS: The median (range) age and F/M sex ratios for patients and controls were 54 years (23-62), 2/8, and 33 years (21-51), 6/6, respectively. The best total cortisol cut-off during low dose cosyntropin test, medium dose cosyntropin test, 30 min and 60 min standard dose cosyntropin test were 14.6 µg/dL (100% sensitivity & specificity), 18.7 µg/dL (100% sensitivity, 88% specificity), 16.1 (100% sensitivity & specificity), and 19.5 µg/dL (100% sensitivity & specificity), respectively. There was no difference in the ROC curve for cortisol values between the cosyntropin stimulation tests (p > 0.41). Using a cortisol cut-off of 18 µg/dL during cosyntropin stimulation tests, only cortisol level at 30 min during standard dose cosyntropin test provided discrimination similar to insulin tolerance test. The best peak free cortisol cut-off levels were 1 µg/dL for insulin tolerance test, 0.9 µg/dL for low dose cosyntropin test, 0.9 µg/dL for medium dose cosyntropin test, and 0.9 µg/dL and 1.3 µg/dL for 30 min and 60 min standard dose cosyntropin test, respectively. CONCLUSION: All cosyntropin stimulation tests had excellent correlations with insulin tolerance test, when appropriate cut-offs were used. This pilot study does not suggest an advantage in using 25 µg cosyntropin dose during the cosyntropin stimulation test. A serum free cortisol cut-off of 0.9 µg/dL may be used as pass criterion during low dose cosyntropin test, standard dose cosyntropin test cosyntropin test, and 30 min standard dose cosyntropin test.

Mutational Analysis in Pediatric Thyroid Cancer and Correlations with Age, Ethnicity, and Clinical Presentation.

BACKGROUND: Well-differentiated thyroid cancer (WDTC) incidence in pediatrics is rising, most being papillary thyroid carcinoma (PTC). The objective of the study was to assess the prevalence of different mutations in pediatric WDTC and correlate the genotype with the clinical phenotype. METHODS: This is a single-center retrospective study. Thyroid tissue blocks from 42 consecutive pediatric WDTC patients who underwent thyroidectomy between 2001 and 2013 were analyzed at Quest Diagnostics for BRAF(V600E), RAS mutations (N,K,H), and RET/PTC and PAX8/PPARγ rearrangements, using validated molecular methods. Thyroid carcinomas included PTC, follicular thyroid carcinoma (FTC), and follicular variant of PTC (FVPTC). RESULTS: Thirty-nine samples (29 females) were genotyped. The mean age at diagnosis was 14.7 years (range 7.9-18.4 years), and most were Hispanic (56.4%) or Caucasian (35.9%). The mean follow-up period was 2.9 years. Mutations were noted in 21/39 (53.8%), with both BRAF(V600E) (n = 9), and RET/PTC (n = 6) detected only in PTC. Mutations were detected in 2/5 FTC (PAX8/PPARγ and NRAS) and 3/6 FVPTC cases (PAX8/PPARγ). Of 28 PTC patients, 57.1% had mutations: 32.1% with BRAF(V600E), 21.4% with RET/PTC, and 3.6% with NRAS. Of patients with BRAF(V600E), 77.8% were Hispanic and 88.9% were >15 years, while all RET/PTC-positive patients were ≤15 years (p = 0.003). Tumor size, lymph node involvement, and distant metastasis at diagnosis (or soon after (131)I ablation) did not vary significantly based on the mutation. CONCLUSIONS: BRAF(V600E) was the most common mutation, especially in older and Hispanic adolescents. A larger, ethnically diverse pediatric cohort followed long term will enable the genotypic variability, clinical presentation, and response to therapy to be better assessed.

Regulation of glucose transport and insulin signaling by troglitazone or metformin in adipose tissue of type 2 diabetic subjects.

Type 2 diabetic subjects failing glyburide therapy were randomized to receive additional therapy with either metformin (2,550 mg/day) or troglitazone (600 mg/day) for 3-4 months. Biopsies of subcutaneous abdominal adipose tissue were obtained before and after therapy. Glycemic control was similar with both treatments. Metformin treatment increased insulin-stimulated whole-body glucose disposal rates by 20% (P < 0.05); the response to troglitazone was greater (44% increase, P < 0.01 vs. baseline, P < 0.05 vs. metformin). Troglitazone-treated subjects displayed a tendency toward weight gain (5 +/- 2 kg, P < 0.05), increased adipocyte size, and increased serum leptin levels. Metformin-treated subjects were weight-stable, with unchanged leptin levels and reduced adipocyte size (to 84 +/- 4% of control, P < 0.005). Glucose transport in isolated adipocytes from metformin-treated subjects was unaltered from pretreatment. Glucose transport in both the absence (321 +/- 134% of pre-Rx, P < 0.05) and presence of insulin (418 +/- 161%, P < 0.05) was elevated after troglitazone treatment. Metformin treatment had no effect on adipocyte content of GLUT1 or GLUT4 proteins. After troglitazone treatment, GLUT4 protein expression was increased twofold (202 +/- 42%, P < 0.05). Insulin-stimulated serine phosphorylation of Akt was augmented after troglitazone (170 +/- 34% of pre-Rx response, P < 0.05) treatment and unchanged by metformin. We conclude that the ability of troglitazone to upregulate adipocyte glucose transport, GLUT4 expression, and insulin signaling can contribute to its greater effect on whole-body glucose disposal.

Differential effects of metformin and troglitazone on cardiovascular risk factors in patients with type 2 diabetes.

OBJECTIVE: Traditional cardiovascular risk factors (CVRF) only partly explain the excessive risk of cardiovascular disease in patients with type 2 diabetes. There is now an increasing appreciation for many novel CVRF that occur largely as a result of insulin resistance and hyperinsulinemia. Therefore, we investigated whether diabetes medications that vary in their mechanism of action and ability to reduce insulin resistance may differ in their effects on both traditional and novel CVRF. RESEARCH DESIGN AND METHODS: We compared the addition of metformin or troglitazone therapy on CVRF in 22 subjects with type 2 diabetes who remained in poor glycemic control (with HbA1c >8.5%) while taking glyburide 10 mg twice daily. Subjects were initially randomized to either metformin 850 mg once daily or troglitazone 200 mg once daily. Both medications were then titrated upward as needed to achieve fasting plasma glucose <120 mg/dl. Measures of glucose control, insulin resistance, and CVRF (blood pressure, lipids, plasminogen activator inhibitor-1, C-reactive protein, fibrinogen, and small dense LDL) were assessed both before and after therapy. RESULTS: After 4 months of treatment, both metformin and troglitazone led to similar decreases in fasting plasma glucose and HbA1c. The reduction in insulin resistance determined by hyperinsulinemic-euglycemic clamp was nearly twofold greater with troglitazone than metformin. Metformin did not induce significant changes in blood pressure, LDL cholesterol, LDL size, HDL cholesterol, triglycerides, or plasminogen activator inhibitor-1. However, C-reactive protein did decrease by 33% (6 +/- 1 to 4 +/- 1 mg/l; P < 0.01) [corrected]. Troglitazone therapy was associated with increases in LDL size (26.21 +/- 0.22 to 26.56 +/- 0.25 nm; P=0.04) and HDL cholesterol (33 +/- 3 to 36 +/- 3 mg/dl; P=0.05) and decreases in triglycerides (197 +/- 19 to 155 +/- 23 mg/dl; P=0.07) and C-reactive protein by 60% (8 +/- 3 to 3 +/- 1 mg/l, P < 0.01) [corrected]. CONCLUSIONS: For patients with type 2 diabetes in whom maximal sulfonylurea therapy failed, the addition of the insulin sensitizer troglitazone seemed to have greater benefits on several traditional and novel CVRF than metformin therapy. These differences were not related to glycemic improvement but reflected, in part, the greater reduction in insulin resistance obtained with addition of troglitazone. These data suggest that medications that more effectively address this underlying metabolic defect may be more beneficial in reducing cardiovascular risk in type 2 diabetes.

Injectable dexamethasone sodium phosphate administered orally? A pharmacokinetic analysis of a common emergency department practice.

BACKGROUND: The injectable formulation of dexamethasone has been administered orally, for the treatment of pediatric asthma and croup. The practice is followed in emergency departments around the country, but pharmacokinetic data supporting this practice are lacking. OBJECTIVES: This study evaluated the relative bioavailability and pharmacokinetics of dexamethasone sodium phosphate for injection (DSPI) administered orally compared to dexamethasone oral concentrate (DOC) in healthy adults. METHODS: This was an open label, crossover study of 11 healthy adults 18 to 45 years of age. All subjects received 8 mg of dexamethasone oral concentrate initially. After a 1-week wash-out period, subjects received 8 mg of DSPI administered orally. Dexamethasone levels were measured by liquid chromatography in tandem mass spectrometry. Cmax and area under the curve (AUC (0-t) and AUC (0-∞)) were calculated and compared between groups using the paired t test. RESULTS: The mean ± SD AUC(0-t) for dexamethasone oral concentrate and DSPI were 5497.23 ± 1649 and 4807.82 ± 1971) ng/dL/hr, respectively; 90% confidence interval (CI) was 78.8%-96.9%. The mean ± SD AUC(0-∞) for dexamethasone oral concentrate and DSPI were 6136.43 ± 2577 and 5591.48 ± 3075 ng/dL/hr, respectively; 90% CI was 79.0% -105.2%. Mean Cmax ± SD for DOC and DSPI were 942.94 ± 151 and 790.92 ± 229 ng/dL, respectively; 90% CI 76.8%-91.7%. The relative bioavailability of DSPI administered orally was 87.4% when using AUC(0-t) and 91.1% when using AUC(0-∞). The calculated absolute bioavailability was 75.9%. CONCLUSIONS: DSPI is not bioequivalent to dexamethasone oral concentrate when administered orally. The existing literature supports the efficacy of DSPI despite this. Dosing adjustments may be considered.

Temporal relationship between vitamin D status and parathyroid hormone in the United States.

BACKGROUND: Interpretation of parathyroid hormone (iPTH) requires knowledge of vitamin D status that is influenced by season. OBJECTIVE: Characterize the temporal relationship between 25-hydroxyvitamin D3 levels [25(OH)D3] and intact iPTH for several seasons, by gender and latitude in the U.S. and relate 25-hydrovitamin D2 [25(OH)D2] levels with PTH levels and total 25(OH)D levels. METHOD: We retrospectively determined population weekly-mean concentrations of unpaired [25(OH)D2 and 25(OH)D3] and iPTH using 3.8 million laboratory results of adults. The 25(OH)D3 and iPTH distributions were normalized and the means fit with a sinusoidal function for both gender and latitudes: North >40, Central 32-40 and South <32 degrees. We analyzed PTH and total 25(OH)D separately in samples with detectable 25(OH)D2 (≥4 ng/mL). FINDINGS: Seasonal variation was observed for all genders and latitudes. 25(OH)D3 peaks occurred in September and troughs in March. iPTH levels showed an inverted pattern of peaks and troughs relative to 25(OH)D3, with a delay of 4 weeks. Vitamin D deficiency and insufficiency was common (33% <20 ng/mL; 60% <30 ng/mL) as was elevated iPTH levels (33%>65 pg/mL). The percentage of patients deficient in 25(OH)D3 seasonally varied from 21% to 48% and the percentage with elevated iPTH reciprocally varied from 28% to 38%. Patients with detectable 25(OH)D2 had higher PTH levels and 57% of the samples with a total 25(OH)D > 50 ng/mL had detectable 25(OH)D2. INTERPRETATION: 25(OH)D3 and iPTH levels vary in a sinusoidal pattern throughout the year, even in vitamin D2 treated patients; 25(OH)D3, being higher in the summer and lower in the winter months, with iPTH showing the reverse pattern. A large percentage of the tested population showed vitamin D deficiency and secondary hyperparathyroidism. These observations held across three latitudinal regions, both genders, multiple-years, and in the presence or absence of detectable 25(OH)D2, and thus are applicable for patient care.

Variability and reliability of single serum IGF-I measurements: impact on determining predictability of risk ratios in disease development.

In recent years, a number of investigators have studied the relationship between IGF-I and risk of developing cancer, diabetes or cardiovascular disease. Upper tertile, quartile, and quintile IGF-Is were associated with higher risk of developing cancer, and lowest quartile with cardiac disease and diabetes. As part of a study to correlate serum IGF-Is and growth hormone dynamics in aging, we measured fasting serum IGF-I at baseline and two weeks later in a group of 84 normal volunteers between the ages of 50 and 90 years. Although the correlation between the two IGF-Is was high (r=0.922; p<0.0001) there were substantial differences between the two IGF-I values ranging from -36.25 to +38.24% between individual IGF-I values at the two blood draws and a significant difference between the mean IGF-Is at visits I and 2 (mean 120.28+/-53.5 vs. 114.95+/-50.03; p=0.03). When considered in quartiles, IGF-I changed from one quartile to another in 34/84 (40.5%) of the volunteers. When the group was divided in halves, tertiles,quartiles, or quintiles there was an increasing number of subjects who changed from one subdivision to another as the number of gradations increased. These results suggest that the predictive outcomes of earlier studies that used single IGF-I samples for analysis of risk ratios according to tertiles, quartiles, or quintiles could have been different if a second IGF-I was used to establish the risk ratio. The results also suggest that variability in IGF-I should be taken into account when designing such studies.