Asymptomatic elevated parathyroid hormone level due to immunoassay interference.

BACKGROUND: Parathyroid hormone (PTH) measurement using immunoassays is inherently vulnerable to interferences due to the presence of different proteins such as heterophile antibodies, human anti-animal antibodies, auto-analyte antibodies, the rheumatoid factor, and others. The frequency of immunoassay interference can be as high as 6%. We report the case of a patient showing persistent high levels of PTH without impact on calcium and bone metabolism. CASE PRESENTATION: The patient was a 59-year-old asymptomatic woman who consistently showed elevated PTH levels (385-482 pg/ml) using the Roche Elecsys (Cobas e-411) and ADVIA Centaur assays, with normal calcium, phosphorus, vitamin D, and renal function parameters. She had no history of fractures, nephrolithiasis, gastrointestinal complaints, renal insufficiency, or autoimmune diseases. Her physical examination revealed no abnormalities. Biomarkers of bone metabolism were within the reference range. To rule out falsely elevated PTH levels, we initially performed serial dilutions using both assays, which revealed nonlinearity. After a polyethylene glycol precipitation test, less than 10% of PTH was recovered from the supernatant. These results suggested the presence of heterophile antibodies as the cause of the falsely elevated PTH levels. CONCLUSION: Physicians should be aware of this issue in order to avoid unnecessary clinical investigations and inappropriate treatments.

Structural basis for Aß1­42 toxicity inhibition by Aß C-terminal fragments: discrete molecular dynamics study.

Amyloid ß-protein (Aß) is central to the pathology of Alzheimer's disease. Of the two predominant Aß alloforms, Aß(1-40) and Aß(1-42), the latter forms more toxic oligomers. C-terminal fragments (CTFs) of Aß were recently shown to inhibit Aß(1-42) toxicity in vitro. Here, we studied Aß(1-42) assembly in the presence of three effective CTF inhibitors and an ineffective fragment, Aß(21-30). Using a discrete molecular dynamics approach that recently was shown to capture key differences between Aß(1-40) and Aß(1-42) oligomerization, we compared Aß(1-42) oligomer formation in the absence and presence of CTFs or Aß(21-30) and identified structural elements of Aß(1-42) that correlated with Aß(1-42) toxicity. CTFs co-assembled with Aß(1-42) into large heterooligomers containing multiple Aß(1-42) and inhibitor fragments. In contrast, Aß(21-30) co-assembled with Aß(1-42) into heterooligomers containing mostly a single Aß(1-42) and multiple Aß(21-30) fragments. The CTFs, but not Aß(21-30), decreased the ß-strand propensity of Aß(1-42) in a concentration-dependent manner. CTFs and Aß(21-30) had a high binding propensity to the hydrophobic regions of Aß(1-42), but only CTFs were found to bind the Aß(1-42) region A2-F4. Consequently, only CTFs but not Aß(21-30) reduced the solvent accessibility of Aß(1-42) in region D1-R5. The reduced solvent accessibility of Aß(1-42) in the presence of CTFs was comparable to the solvent accessibility of Aß(1-40) oligomers formed in the absence of Aß fragments. These findings suggest that region D1-R5, which was more exposed to the solvent in Aß(1-42) than in Aß(1-40) oligomers, is involved in mediating Aß(1-42) oligomer neurotoxicity.

Nuevos factores que intervienen en la regulación de la 1 alfa hidroxilasa renal de la vitamina D / New factors which regulate renal vitamin D1 alfa hydroxylase

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[Whole PTH and 1-84/84 PTH ratio for the non invasive determination of low bone turnover in renal osteodysthrophy]. / Utilidad de la determinación de PTH entera y del cociente PTH 1-84/7-84 en el diagnóstico no invasivo de osteodistrofia de bajo recambio.

The conventional intact PTH assays detect not only PTH 1-84 but also inactive fragments (as PTH 7-84) that accumulate in renal failure. There has been a recent development of a new PTH assay that measures only true 1-84 PTH (Whole PTH or CAP assay, Scantibodies). As 7-84 PTH fragment is antagonistic on bone effects of 1-84 PTH, Moniere-Faugere has suggested that 1-84/7-84 PTH ratio less than 1 is predictive of low turnover. We evaluated the usefulness of CAP assay and the 1-84/7-84 PTH ratio as markers of bone turnover in a groups of 24 patients in peritoneal dialysis (PD). Patients were classified as having low bone turn over if they had a Total PTH (similar to intact PTH) of less than 100 pg/ml. We also measured serum CrossLaps (CTX) as another serum resorption marker. Patients had a mean Whole PTH of 95.5 pg/ml and a mesan total PTH of 155.4 pg/l (range 9 to 900). Whole PTH represented 69.1% of total PTH. Fifteen patients (62.5%) had a total PTH of less than 100. These patients had a 1-84/7-84 relationship of 1.9 +/- 1.8 while 9 patients with Total PTH more than 100 had a relationship of 1.29 +/- 0.6 (p = NS). There was a tight correlation between Whole PTH and total PTH (r = 0.98; p < 0.0001) and with serum CTX (r = 0.78; p < 0.0001). We conclude that 1-84/7-84 ratio does not seem useful in the prediction of low bone turnover and that Whole PTH does not seem to be more useful than intact PTH in the prediction of bone turnover in this population. Future studies should correlate this markers with direct measurements of bone turnover in bone biopsies to demonstrate their usefulness in the prediction of the type of renal osteodystrophy.

Utilidad de la determinación de PTH entera y del cociente PTH 1-84/7-84 en el diagnóstico no invasivo de osteodistrofia de bajo recambio / Whole PTH and 1-84/7-84 PTH ratio for the non invasive determination of low bone turnover in renal osteodystrophy

Los ensayos convencionales de PTH intacta detectan tanto la PTH 1-84 como fragmentos inactivos (como la PTH 7-84) que se acumula en insuficiencia renal. Recientemente se ha desarrollado un nuevo ensayo de PTH que mide solo la verdadera PTH 1-84 (PTH entera, Whole PTH o CAP assay, Scantibodies). Como el fragmento PTH 7-84 es antagónico sobre los efectos óseos de la PTH 1-84, Moniere-Faugere han sugerido que un cociente PTH 1-84/7-84 menor a 1 podría predecir bajo recambio óseo. Nosotros evaluamos la utilidad del ensayo de PTH entera y de la relación PTH 1-84/7-84 como marcadores de recambio óseo en un grupo de 24 pacientes en diálisis peritoneal (DP). Los pacientes se clasificaron como que presentaban bajo recambio óseo si tenían una PTH total (ensayo similar a la PTH intacta) de menos de 100 pg/ml. También medimos los Crosslaps (CTX) séricos como otro marcador de resorción. Los pacientes tuvieron una media de PTH entera de 95,5 pg/ml y una media de PTH total de 155,4 pg/ml (rango 9 a 900). La PTH entera representó el 69,1% de la PTH total. Quince pacientes (62,5%) tuvieron una PTH total menor a 100. Estos pacientes tuvieron cociente PTH 1-84/7-84 de 1,9 ± 1,8 mientras que 9 pacientes con una PTH total mayor a 100 tuvieron un cociente de 1,29 ± 0,6 (p = NS). Hubo una estrecha correlación entre PTH entera y PTH total 9 r = 0,98; p < 0,0001) y con los CTX séricos (r = 0,78; p < 0,0001). Nosotros concluimos que el cociente 1-84/7-84 no parece ser útil en la predicción bajo recambio óseo y que la PTH total no parece ser más útil que la PTH intacta en la predicción del recambio óseo en esta población. Futuros estudios deberán correlacionar estos marcadores con mediciones directas del recambio óseo en biopsias óseas para demostrar su utilidad en la predicción del tipo de osteodistrofia renal

The conventional intact PTH assays detect not only PTH 1-84 but also inactive fragments (as PTH 7-84) that accumulate in renal failure. There has been a recent development of a new PTH assay that measures only true 1-84 PTH (Whole PTH or CAP assay, Scantibodies). As 7-84 PTH fragment is antagonistic on bone effects of 1-84 PTH, Moniere-Faugere has suggested that 1-84/7-84 PTH ratio less than 1 is predictive of low turnover. We evaluated the usefulness of CAP assay and the 1-84/7-84 PTH ratio as markers of bone turnover in a groups of 24 patients in peritoneal dialysis (PD). Patients were classified as having low bone turn over if they had a Total PTH (similar to intact PTH) of less than 100 pg/ml. We also measured serum CrossLaps (CTX) as another serum resorption marker. Patients had a mean Whole PTH of 95.5 pg/ml and a mesan total PTH of 155.4 pg/l (range 9 to 900). Whole PTH represented 69.1% of total PTH. Fifteen patients (62.5%) had a total PTH of less than 100. These patients had a 1-84/7-84 relationship of 1.9 ± 1.8 while 9 patients with Total PTH more than 100 had a relationship of 1.29 ± 0.6 (p = NS). There was a tight correlation between Whole PTH and total PTH ( r = 0.98; p < 0.0001) and with serum CTX ( r = 0,78; p < 0,0001). We conclude that 1-84/7-84 ratio does not seem useful in the prediction of low bone turnover and that Whole PTH does not seem to be more useful than intact PTH in the prediction of bone turnover in this population. Future studies should correlate this markers with direct measurements of bone turnover in bone biosies to demonstrate their usefulness in the prediction of the type of renal osteodystrophy

Estimación de la prevalencia de osteodistrofia renal de bajo recambio a través de marcadores bioquímicos en una población en diálisis peritoneal / Estimation of the prevalence of adynamic bone disease using biochemical markers

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Vitamin D and bone mineral density in ambulatory women living in Buenos Aires, Argentina.

The aim of this study was to determine possible associations between bone mineral density (BMD), 25-hydroxyvitamin D (25(OH)D) and intact parathyroid hormone (PTH). In a retrospective study we examined the case notes of free-living postmenopausal women living in our city (34 degrees S). We also report a low prevalence of vitamin D deficiency (25(OH)D < 25 nmol/1, 5.6%) and of secondary hyperparathyroidism (intact PTH > 65 pg/ml, 7.5%). Age was correlated with BMD at the lumbar spine (r = -0.25, p = 0.00038) and femoral neck (r = -0.252, p = 0.0003). Body mass index (BMI) was correlated with BMD at the femoral neck (r = 0.177, p = 0.021) but not at the lumbar spine. 25(OH)D was positively correlated with BMD at the femoral neck (r = 0.149, p = 0.036) but not at the lumbar spine. PTH was positively correlated with age (r = 0.279, p = 0.012) and negatively correlated with 25(OH)D (r = -0.322, p = 0.0036). PTH was also negatively correlated with BMD at the lumbar spine (r = -0.258, p = 0.02) and the femoral neck (r = -0.282, p = 0.011). Forward stepwise multiple regression showed that BMI, age and 25(OH)D made significant contributions to BMD at the femoral neck. PTH also showed a significant contribution to BMD at both sites. In conclusion, weak correlations found between PTH and 25(OH)D and BMD suggest these biochemical variables, among other factors, contribute to lumbar spine and femoral neck BMD.

Early expression of pituitary adenylate cyclase-activating polypeptide and activation of its receptor in chick neuroblasts.

To investigate the involvement of pituitary adenylate cyclase- activating polypeptide (PACAP) and GH-releasing factor (GRF) during early chick brain development, we established neuroblast- enriched primary cell cultures derived from embryonic day 3.5 chick brain. We measured increases in cAMP generated by several species-specific forms of the peptides. Dose-dependent increases up to 5-fold of control values were measured in response to physiological concentrations of human/salmon, chicken, and tunicate PACAP27. Responses to PACAP38 were more variable, ranging from 5-fold for human PACAP38 to 4-fold for chicken PACAP38, to no significant response for salmon PACAP38, compared with control values. The responses to PACAP38 may reflect a greater difference in peptide structure compared with PACAP27 among species. Increases in cAMP generated by human, chicken, and salmon/carp GRF were not statistically significant, whereas increases in response to lower-range doses of tunicate GRF27-like peptide were significant, but small. We also used immunocytochemistry and Western blot to show synthesis of the PACAP38 peptide. RT-PCR was used to demonstrate that messenger RNAs for PACAP and GRF and a PACAP-specific receptor were present in the cells. This is a first report suggesting an autocrine/paracrine system for PACAP in early chick brain development, based on the presence of the ligand, messages for the ligand and receptor, and activation of the receptor in neuroblast-enriched cultures.

Characterization of the gene encoding both growth hormone-releasing hormone (GRF) and pituitary adenylate cyclase-activating polypeptide (PACAP) in the zebrafish.

The purpose of this research was to isolate and characterize the gene encoding growth hormone-releasing hormone (GRF) and pituitary adenylate cyclase-activating polypeptide (PACAP) from the zebrafish. The gene is comprised of five exons with two distinct peptides encoded on separate exons, GRF on exon 4 and PACAP on exon 5. Our evidence indicates that the zebrafish genome contains a single copy of the GRF-PACAP gene. The tissue distribution pattern of the mRNA transcript shows expression in the brain, eye, gastrointestinal tract, ovary and testis; each transcript was sequenced and found to be identical to the gene. This is the first report of GRF-PACAP mRNA expression in the eye of a non-mammalian species. Evidence that a duplication of the PACAP gene gave rise to the vasoactive intestinal peptide (VIP) gene is supported by the high amino acid sequence identity between PACAP in zebrafish and VIP in other fish species.

Calcium bioavailability and parathyroid hormone acute changes after oral intake of dairy and nondairy products in healthy volunteers.

This study was designed to compare calcium bioavailability and serum parathyroid hormone acute changes after oral intake of 500 mg of elemental calcium from liquid milk, yogurt, calcium-citrate-enriched powdered milk or a calcium carbonate pill; or after intake of soybean imitation-milk. After a 12-h fast, blood samples were drawn both at baseline and 1, 2, 3 and 4 h after an oral intake of the above-mentioned products, which were ingested together with a light neutral breakfast. The administration order of the study products was randomly assigned to each of 19 healthy young volunteers (11 females, 8 males). The baseline serum concentrations of ionized calcium, phosphorus and intact parathyroid hormone (iPTH) were normal. Calcium-citrate-enriched powdered milk induced a significant increase in serum ionized calcium (p<0.001) and a significant and continuous decrease in serum iPTH concentration (p<0. 001). Yogurt and the calcium carbonate pill induced a similar but less significant effect, increasing serum ionized calcium (p<0.05) and decreasing serum iPTH (p<0.01). Liquid milk only induced a significant change in serum ionized calcium and iPTH concentration during the first 2 h; this effect was lost during the following 2 h. In conclusion, our study suggests the possibility that the addition of calcium citrate to powered milk may improve calcium bioavailability and enhance the inhibitory effect on serum iPTH in the assayed conditions.

Influence of age and sex in serum osteocalcin levels in thoroughbred horses.

In this study, we assessed the potential value of free serum osteocalcin or bone gla protein (BGP), the most abundant non collagenous matrix protein found in bone and dentin, to reflect changes of bone turnover in thoroughbred horses. Levels of osteocalcin were analyzed in serum samples of 54 clinically normal animals divided into three groups (A, B, C) according to age: 8, 16-18 and 24-36 months, in order to determine the standard for young horses of different age and sex. Serum BGP was measured by an in-house developed double antibody radioimmunoassay using bovine antigen. The mean BGP levels (ng/ml) were 45.65 +/- 11.69; 33.65 +/- 16.65; 15.08 +/- 6.70 respectively for groups A, B and C; statistically significant differences were found between groups (A vs B and C; Bvs C). Difference between males and females was found significant in group C with higher values in the females: 18.75 +/- 5.00 against 14.43 +/- 10.47 i n the males. This can be considered a sex related effect on BGP serum levels after the onset of puberty. Correlation coefficient between age and serum BGP for females and males were r 5 20.598 ( P < 0.001) and r 5 200.807 (P < 0.001) respectively. A significant negative linear relationship could be established between these two parameters in males during the growth period. The regression equation between serum BGP and age for males was (month of age = 65.14-1.68. BGP). In the female group the gestation and lactation are variables that lower the correlation coefficient between age and serum BGP levels. These results suggest that serum BGP decreases in thoroughbred horses during the growth period, and significant differences between sexes were found only after the onset of puberty.

[Vitamin D status in women living in Buenos Aires]. / Niveles de vitamina D en mujeres de la ciudad de Buenos Aires.

Bone loss has both age-related and menopausal components. The causes of age-related bone loss are multifactorial. In order to establish vitamin D status in women in our city (34 degrees S), calcidiol levels were assessed in 357 ambulatory women aged 40-90 years. One hundred and eighty were evaluated during summer time and 177 during winter time. We also evaluated intact PTH values in a subgroup of 231 women and this allowed us to document the prevalence of secondary hyperparathyroidism. Summer levels of calcidiol were significantly higher than in winter: 25.3 +/- 8.5 vs 21.3 +/- 7.4 ng/ml (p < 0.001). We found 4.4% of calcidiol levels < 10 ng/ml (2.2% in summer and 6.6% in winter). Prevalence of calcidiol between 10-20 ng/ml reached 67% in winter and went down to 25% during summer. Prevalence of secondary hyperparathyroidism was 5.2%. Even though prevalence of vitamin D deficiency was low, a great proportion of ambulatory women had calcidiol levels between 10-20 ng/ml. These values would not be sufficient for elderly people and could result in increased calcium mobilisation and further bone loss.

[Treatment of post menopausal osteoporosis with intravenous pamidronate in patients with esophagogastric pathology]. / Tratamiento de la osteoporosis postmenopáusica con pamidronato intravenoso en pacientes con patología esofagogástrica.

Pamidronate is an effective inhibitor of bone resorption; for this reason it is used in the treatment of high bone turnover diseases and osteoporosis. Because of potential gastric and esophagic side effects their oral use is limited in patients with active pathology in these organs. With the aim to evaluate the usefulness and to establish the ideal schedule of treatment of intravenous pamidronate, we assayed pamidronate infusions (APDIV) in 20 postmenopausal women with active gastroesophagical diseases. Ten of these patients received 30 or 45 mg weekly until they achieved an average dose of 157.50 +/- 9.28 mg/year in one month (range: 120-180 mg) (Group A). Another comparable ten women's group received 30 or 45 mg every three months or 90 mg every six months; the achieved average dose in this group was 166.50 +/- 6.87 mg/year (range: 120-180 mg) (Group B). All patients received 1,000 mg elemental calcium daily. Bone mineral density in lumbar spine significantly increased in both groups, but this increment (delta DMO%) was higher in group B. Bone mineral density in femoral neck was only increased in group A. Parathyroid hormone (iPTH) significantly increased at the third month but returned to basal values at the end of the year in both groups. Parameters of bone remodeling such as osteocalcin (BGP), pyridinoline and deoxipyridinolin decreased progressively and remained low at the end of the year. The treatment was well tolerated: only two patients in group A and one in Group B experienced fever and pseudoflu syndrome; phlebitis was present in one patient in the second group. In conclusion, intravenous Pamidronate is an effective and safe treatment for postmenopausal osteoporosis specially in these patients with esophagicor gastric disorders. Future trials are needed to clarify the ideal dose and schedule of treatment.