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Context Vertebral fracture (VF) prevalence up to 24% has been reported among young people with type 1 diabetes (T1D). If this high prevalence is confirmed, individuals with T1D could benefit from preventative VF screening. Objective We compared the prevalence of VFs between adults with T1D and nondiabetic controls. Methods This cross-sectional study included 127 adults with T1D, and 65 controls with a similar age, sex, and BMI distribution, from outpatient clinics of 2 tertiary care centers. Vertebral fracture assessment (VFA) by dual-energy x-ray absorptiometry (DXA) was used for prevalent VFs. The modified algorithm-based qualitative (mABQ) method was applied. Bone mineral density (BMD) and trabecular bone score (TBS) were assessed by DXA. Serum bone turnover markers and sclerostin were measured in a subgroup of participants. Results Participants with T1D (70 women, 57 men) had a mean age of 42.8 ± 14.8 years, median diabetes duration of 25.8 (15.8-34.4) years, mean BMI of 26.6 ± 5.4 kg/m2 and mean HbA1c over the past 3 years of 7.5 ± 0.9%. Controls (35 women, 30 men) had mean age of 42.2 ± 15.9 years and mean BMI of 26.1 ± 5.1 kg/m2. VF prevalence was comparable between groups (2.4% vs 3.1%, P = 0.99). TBS, BMD at the total hip and femoral neck, and bone formation and resorption markers were lower while sclerostin levels were similar in participants with T1D vs controls. Conclusion Our VFA results using the mABQ method do not confirm increased prevalence of VFs in men and women with relatively well-controlled T1D.

The adult bone is continuously being remodelled to repair microdamage, preserve bone strength and mechanical competence as well as maintain calcium homeostasis. Bone turnover markers are products of osteoblasts (bone formation markers) and osteoclasts (bone resorption markers) providing a dynamic assessment of remodelling (turnover). Resorption-specific bone turnover markers are typically degradation products of bone collagen molecules (N- [NTX] and C-telopeptide cross-linked type 1 collagen [CTX]), which are released into the circulation and excreted in urine; or enzymatic activities reflecting osteoclastic resorption, tartrate-resistant acid phosphatase [TRACP]. Formation-specific bone turnover markers embrace different osteoblastic activities: type 1 collagen synthesis (Procollagen type I N- propeptide [PINP]), osteoblast enzymes (bone-specific alkaline phosphatase [BALP]), or bone matrix proteins [osteocalcin]. Among individuals not receiving osteoporosis treatment, resorption and formation markers are tightly linked and highly correlated (r = 0.6-0.8). Significant biological variability was reported in the past, but these issues have been greatly improved with automated assays and attention to pre-analytical and analytical factors that are known to influence bone turnover marker levels. Bone turnover markers are not useful in the diagnosis of osteoporosis, the individual prediction of bone loss, fracture, or rare complications, or in the selection of pharmacological treatment. Despite remaining issues with reference intervals and assays harmonization, bone turnover markers have proven to be useful in elucidating the pharmacodynamics and effectiveness of osteoporosis medications in clinical trials. As an alternative to BMD testing, BTMs may be useful to monitor osteoporosis therapies.

The quantitative evaluation of circulating PTH peaks revealed by PTH assays after HPLC separation constitutes the best way to study the behavior of PTH molecular forms, but it is also impractical.The objective of the study was to investigate the regulation of circulating PTH molecular forms by calcium through the use of PTH fragments/PTH (1-84) ratios derived from PTH assays with different specificities before and after HPLC separation of circulating PTH.CaCl2 and Na citrate were infused in eight volunteers. PTH was measured in serum and HPLC fractions at different calcium concentrations in PTH assays reacting with regions 1-2 (CA), 12-18 (T), and 65-69 (C) of the PTH structure.From hypo- to hypercalcemia, the C/CA ratio had the highest range (1.92 to 9.75; P0.001), and the C/T ratio had a higher range (1.69 to 6.11; P0.01) than the T/CA ratio (1.15 to 1.86). Human (h) PTH (1-84) represented 32.7 and 4.3% of circulating PTH in hypo- and hypercalcemic HPLC profiles, respectively. These numbers were 5 and 0.9% for amino-terminal (N)-PTH, an amino-terminal form of PTH distinct from hPTH (1-84), 7.3 and 6.8% for non-(1-84) PTH or large C-PTH fragments with a partially preserved N structure, and 54.9 and 88.1% for C-PTH fragments missing a N structure. The HPLC C-PTH fragments to hPTH (1-84) ratio had the most extensive range (1.67 to 20.58). Despite their quantitative differences, all ratios identified identical behavior of PTH fragments relative to PTH (1-84).PTH assay ratios are an adequate tool to investigate the modulation of PTH molecular forms, even if all PTH assays show some undesirable cross-reactivity with certain circulating forms of PTH.

Background: Non-(1–84) parathyroid hormone (PTH) fragments are large C-terminal fragments of PTH with a partially preserved N-terminal structure. They differ from other C-terminal PTH fragments, which do not have an N-terminal structure and do not react in intact PTH assays. We aimed to identify the minimal N-terminal structure common to all non-(1–84) PTH fragments.Methods: Sera obtained from six healthy individuals and six patients with primary hyperparathyroidism, and six serum pools from dialysis patients with different PTH concentrations were fractionated by HPLC and analyzed by four different PTH assays. Each assay was characterized by saturation analysis of its detection antibody and capacity to react with different PTH fragments. Human PTH(1–84) [hPTH(1–84)] calibrators were normalized to an in-house hPTH(1–84) calibrator.Results: The cyclase-activating PTH (CA-PTH) assay had an early (1, 2,) epitope and reacted only with hPTH(1–84). The other assays had epitopes in region (13–34). Total and intact PTH assays had epitopes proximal to position 18 and reacted equally well with hPTH(1–84) and hPTH(7–84), and the Elecsys PTH assay had an epitope distal to position 19, being saturable by hPTH(18–48) and also reacting with [Tyr34]hPTH(19–84). The HPLC profiles obtained with these assays showed that non-(1–84) PTH fragments did not react in the CA-PTH assay, as expected. The amount of non-(1–84) PTH detected by the other three assays was similar when the assay results were normalized to a common calibrator.Conclusions: The results suggest that the amount of non-(1–84) PTH detected by epitopes proximal or distal to position 19 of the PTH structure is identical, indicating a common minimum structure starting before position 19. This in turn points to a probable high-affinity interaction with the C-PTH receptor, as observed previously with [Tyr34]hPTH(19–84) in various cell lines and in mouse osteocytes with PTH/PTHrP type I receptor ablation.

In recent years, the enzymes which are involved in the formation of DHT in steroid target tissues have been well investigated, however, enzymes responsible for the catabolism and elimination of steroids in these tissues, in particular the uridine diphospho-glucuronosyltransferase (UGT) family of enzymes, have received much less attention. We have recently demonstrated that human and monkey are unique in having high plasma levels of C19 steroid glucuronides. These circulating conjugates have been proposed to reflect the peripheral conversion of adrenal and gonadal C19 steroids to potent androgens, especially DHT. In humans, the presence of steroid UGT activities is found in the liver and several extrahepatic tissues including the prostate, mammary gland and ovary. In addition, UGT activities were observed in breast and prostate tumor cell lines such as MCF-7 and LNCaP, respectively. In agreement with the presence of steroid conjugating enzymes in extrahepatic tissues, UGT cDNA clones, which encode steroid conjugating proteins, have been isolated from libraries constructed from human and monkey prostate mRNA. The presence of UGT transcripts and proteins in extrahepatic tissues in both species, as determined by Northern blot, ribonuclease protection, specific RT-PCR, in situ hybridization, Western blot and immunocytochemistry analysis, indicate the relevance of steroid glucuronidation in tissues other than the liver. Knowing that both the human prostate and the human prostate cancer LNCaP cell line express steroid metabolizing proteins, including UGT enzymes, regulation of UGT mRNA and protein levels, as well as promoter activity was studied in these cells. The results demonstrate a differential regulation between the two highly related isoforms UGT2B15 and UGT2B17, where only the expression of UGT2B17 was affected following treatments of LNCaP cells with androgens, growth factors or cytokines. Steroid conjugation by UGT enzymes is potentially involved in hormone inactivation in steroid target tissues, thus modifications in UGT expression levels may influence hormonal responses.

Osteoporosis is the most common cause of fragility fractures. Bone remodelling is essential for repairing damaged areas within bone to preserve bone strength and for assisting in mineral homeostases. In young adults, bone remodelling is usually balanced with approximately as much bone replaced as is removed during each remodelling cycle. However, when remodelling becomes accelerated in combination with an imbalance that favours bone resorption over formation, such as during menopause, precipitous losses in bone mass occur. Bone turnover markers (BTMs) measure the rate of bone remodelling allowing for a dynamic assessment of skeletal status and hold promise in identifying those at highest risk of rapid bone loss and subsequent fracture. Further, the use of BTMs to monitor individuals administered osteoporosis therapy is attractive as monitoring anti-fracture efficacy with bone mineral density has significant limitations. This review details remodelling biology, pre-analytical and analytical sources of variability for BTMs, describes the most commonly used resorption and formation markers, and offers some guidelines for their use and interpretation in the laboratory and the clinic.

The MTG-BT estimates the hydrolysis of triacyl-glycerols by pancreatic lipase, and appears attractive for monitoring exogenous lipase requirements in patients with exocrine pancreatic insufficiency. To assess the test's discrimination capacity and repeatability, 9 CF patients with PERT and 10 healthy children underwent the (13)C-MTG-BT twice, at a 2- to 4-week interval. The test distinguished well between patients with severe exocrine pancreatic insufficiency (SEPI) and healthy subjects. However, within-subject variability for postprandial per thousand(13)C-enrichment and postprandial % dose recovery (PDR) was high in both groups. Therefore, the (13)C-MTG-BT seems useful to distinguish between SEPI and normal exocrine pancreatic function, but requires further development to improve its repeatability.

The hormone assay laboratory has seen incredible changes over the last 50 years. In this historical review, we describe how the evolution of fundamental concepts in endocrinology and in hormone assay technology have faceted the laboratory as we know it today. The discovery of neurohormones, hormone receptors and the evolution of the concept of free hormones had a very significant impact on our understanding of the mechanisms of hormone action in health and disease and therefore on how physicians currently prescribe endocrine tests. In the analytical field, modern hormone assays rapidly replaced crude colorimetric methods and bioassays. Starting with the pioneering work of Yalow and Berson, hormone assays have gradually evolved through improvements in all aspects of assay design. This is best exemplified by the evolution of thyroid and parathyroid hormone assays. After reviewing some of the limitations of actual hormone immunoassays, we present some reflections on what the future of the hormone laboratory may look like considering all the developments in automation, point-of-care testing, molecular biology and array technologies.

Although enzymes that catalyze the formation of steroids are well known, less information is available about the enzymes involved in the metabolism of these hormones. Steroid glucuronidation, by UDP-glucuronosyltransferase enzymes, is one mechanism by which steroid hormones can be metabolized and eliminated from a tissue. Previous results suggest that the monkey represents the most appropriate animal model for studying the physiologic relevance of steroid glucuronidating enzymes. The monkey UGT1A01 cDNA clone was isolated by RT-PCR amplification of the liver RNA. The cDNA contains an open reading frame of 1599 bp encoding a protein of 533 residues. The primary structure of monkey UGT1A01 is 95% identical to human UGT1A1. To compare monkey and human UGT1A1 enzymes, both cDNA clones were transfected into HK293 cells and stable cell lines expressing each UGT1A1 protein were established. Western blot analysis of the monUGT1A01-HK293 and hUGT1A1-HK293 cell lines using a anti-UGT1A polyclonal antibody (RC-71) revealed expression of exogenous 55 kDa UGT1 proteins. The transferase activities of monkey and human UGT1A1 proteins were tested with over 60 compounds and were demonstrated to be active on the same compounds. For endogenous compounds only bilirubin and C18 steroids were glucuronidated by these enzymes. Using microsome preparation (from HK293 cell expressing monkey UGT1A01), the apparent K m values were 13, 5 and 6 μM for the conjugation of estradiol, 2-hydroxyestradiol and 2-hydroxyestrone, respectively, and were very similar to the values obtained with human UGT1A1. Specific RT-PCR analysis demonstrated the expression of monkey and human UGT1A1 transcripts in several tissues including liver, kidney, intestine, prostate, testis and ovary suggesting a contribution of this isoenzyme to estrogen metabolism in the cynomolgus monkey as in human.