Impact of the delay in cryopreservation timing during biobanking procedures on human liver tissue metabolomics.

The liver is a highly specialized organ involved in regulating systemic metabolism. Understanding metabolic reprogramming of liver disease is key in discovering clinical biomarkers, which relies on robust tissue biobanks. However, sample collection and storage procedures pose a threat to obtaining reliable results, as metabolic alterations may occur during sample handling. This study aimed to elucidate the impact of pre-analytical delay during liver resection surgery on liver tissue metabolomics. Patients were enrolled for liver resection during which normal tissue was collected and snap-frozen at three timepoints: before transection, after transection, and after analysis in Pathology. Metabolomics analyses were performed using 1H Nuclear Magnetic Resonance (NMR) and Liquid Chromatography-Mass Spectrometry (LC-MS). Time at cryopreservation was the principal variable contributing to differences between liver specimen metabolomes, which superseded even interindividual variability. NMR revealed global changes in the abundance of an array of metabolites, namely a decrease in most metabolites and an increase in ß-glucose and lactate. LC-MS revealed that succinate, alanine, glutamine, arginine, leucine, glycerol-3-phosphate, lactate, AMP, glutathione, and NADP were enhanced during cryopreservation delay (all p<0.05), whereas aspartate, iso(citrate), ADP, and ATP, decreased (all p<0.05). Cryopreservation delays occurring during liver tissue biobanking significantly alter an array of metabolites. Indeed, such alterations compromise the integrity of metabolomic data from liver specimens, underlining the importance of standardized protocols for tissue biobanking in hepatology.

Metabolomics-Guided Identification of a Distinctive Hepatocellular Carcinoma Signature.

BACKGROUND: Hepatocellular carcinoma (HCC) is a major contributor to cancer-related morbidity and mortality burdens globally. Given the fundamental metabolic activity of hepatocytes within the liver, hepatocarcinogenesis is bound to be characterized by alterations in metabolite profiles as a manifestation of metabolic reprogramming. METHODS: HCC and adjacent non-tumoral liver specimens were obtained from patients after HCC resection. Global patterns in tissue metabolites were identified using non-targeted 1H Nuclear Magnetic Resonance (1H-NMR) spectroscopy whereas specific metabolites were quantified using targeted liquid chromatography-mass spectrometry (LC/MS). RESULTS: Principal component analysis (PCA) within our 1H-NMR dataset identified a principal component (PC) one of 53.3%, along which the two sample groups were distinctively clustered. Univariate analysis of tissue specimens identified more than 150 metabolites significantly altered in HCC compared to non-tumoral liver. For LC/MS, PCA identified a PC1 of 45.2%, along which samples from HCC tissues and non-tumoral tissues were clearly separated. Supervised analysis (PLS-DA) identified decreases in tissue glutathione, succinate, glycerol-3-phosphate, alanine, malate, and AMP as the most important contributors to the metabolomic signature of HCC by LC/MS. CONCLUSIONS: Together, 1H-NMR and LC/MS metabolomics have the capacity to distinguish HCC from non-tumoral liver. The characterization of such distinct profiles of metabolite abundances underscores the major metabolic alterations that result from hepatocarcinogenesis.

Nontruncated amino-terminal parathyroid hormone overproduction in two patients with parathyroid carcinoma: a possible link to HRPT2 gene inactivation.

OBJECTIVE: Some patients with parathyroid carcinoma present with an over-production of nontruncated amino-terminal (NT-N) parathyroid hormone (PTH), a post-transcriptionally modified form of PTH(1-84). This is usually picked up on an elevated whole (W) PTH (third-generation)/total (T) (second-generation) PTH assay ratio (N > 0·8). PATIENTS AND DESIGN: Two parathyroid cancer patients with several episodes of hypercalcaemia and multiple surgeries are described. In both patients, W-PTH, T-PTH and circulating PTH molecular forms separated by high-pressure liquid chromatography (HPLC) were measured with the same assays. qPCR was used to study HRPT2 gene mutation. RESULTS: The first patient had total calcium of 3·8 and 3·22 mmol/l before the fourth and fifth surgeries, and third/second-generation PTH ratios of 2·95 and 3·6, respectively. After the fourth surgery, the ratio remained normal for 1 year and increased progressively to 3·6 over 15 months. This preceded hypercalcaemia by 6 months. The ratio became normal after the fifth surgery. HPLC analysis disclosed an over-expression of NT-N PTH to 82·2% (N < 10%) relative to hPTH(1-84) before the fifth surgery. A deletion of all the tested exons of the HRPT2 gene was identified. In the second patient, W-PTH/T-PTH ratio was 0·89 when serum calcium was 3·3 mmol/l. NT-N PTH was also over-expressed at 51·9%. An inactivating mutation of the HRPT2 gene was also identified. CONCLUSIONS: This may suggest that a progressive rise in third/second-generation ratio may have possible clinical utility to monitor parathyroid cancer recurrence. A possible association between NT-N PTH overproduction and HRPT2 gene inactivation is also suggested.

Rat parathyroid hormone (rPTH) ELISAs specific for regions (2-7), (22-34) and (40-60) of the rat PTH structure: influence of sex and age.

Rat (r) PTH ELISAs were used to study the influence of age and sex on rPTH levels and circulating PTH molecular forms separated by HPLC. Standard curves and saturation analysis were undertaken to define epitopes. Rats were sacrificed at approximately 27, 47 and 75days. Relevant biochemical parameters and 25(OH) vitamin D were measured. Differences between sexes were analyzed by Kruskal-Wallis ANOVA, followed by Dunn's test. Epitopes were localized in regions 2-7, 22-34 and 40-60 of rPTH structure for whole (W), total (T) and carboxyl (C) rPTH ELISAs. The W-rPTH assay only detected rPTH(1-84) and N-PTH in circulation while the T-PTH assay further detected large C-rPTH fragments. The C-rPTH assay detected all circulating rPTH molecular forms including smaller C-rPTH fragments. In both sexes, weight (p<0.001), ionized calcium, creatinine, albumin and 25(OH)D values (p<0.001) increased with age, while phosphate and alkaline phosphatase decreased (p<0.001). In male rats, W-rPTH remained unchanged, while T-rPTH rose slightly (p<0.05) and C-rPTH declined by half with time (p<0.001). In female rats, W-rPTH (p<0.05), T-rPTH (p<0.001) and C-rPTH (p<0.01) all increased in older animals. In both sexes, C-rPTH/W-rPTH and C-rPTH/T-rPTH ratios decreased between 25 and 47 days, to rise again between 47 and 75 days. The initial decrease may represent an adaptation to weaning and a change of diet between 25 and 47 days while the rise corresponds to higher calcium and 25(OH)D levels between 47 and 75 days. These changes were more pronounced in female rats, indicating an influence of sex on PTH molecular form secretion or metabolism.

TOCSIN: a proposed dashboard of indicators to control healthcare-associated infections.

Healthcare-associated infections (HAIs) constitute a major safety problem. Healthcare managers need complete and valid information to fight against these infections. The purpose of this study was to develop a dashboard of indicators to help healthcare managers monitor HAIs. A pilot testing approach was used that was composed of the following steps: literature review, consultation with infection control experts and healthcare managers, operationalization of selected indicators, data collection from six Quebec hospital complexes to test the feasibility of the selected indicators and results dissemination. The literature review identified 299 possible indicators. After consulting infection control experts and healthcare managers and having collected data in the hospitals, a proposed dashboard was created that includes 97 indicators divided in three categories (structure, process and outcome) and grouped in 22 themes. The proposed indicators are both scientifically valid and administratively feasible. However, many healthcare facilities need additional financial resources and expertise to measure these indicators and manage the information they will generate.

Failed immune responses across multiple pathologies share pan-tumor and circulating lymphocytic targets.

Rationale Tumor infiltrating lymphocytes are widely associated with positive outcomes, yet carry key indicators of a systemic failed immune response against unresolved cancer. Cancer immunotherapies can reverse their tolerance phenotypes, while preserving tumor-reactivity and neoantigen-specificity shared with circulating immune cells. Objectives We performed comprehensive transcriptomic analyses to identify gene signatures common to circulating and tumor infiltrating lymphocytes in the context of clear cell renal cell carcinoma. Modulated genes also associated with disease outcome were validated in other cancer types. Findings Using bioinformatics, we identified practical diagnostic markers and actionable targets of the failed immune response. On circulating lymphocytes, three genes, LEF1, FASLG, and MMP9, could efficiently stratify patients from healthy control donors. From their associations with resistance to cancer immunotherapies and microbial infections, we uncovered not only pan-cancer, but pan-pathology failed immune response profiles. A prominent lymphocytic matrix metallopeptidase cell migration pathway, is central to a panoply of diseases and tumor immunogenicity, correlates with multi-cancer recurrence, and identifies a feasible, non-invasive approach to pan-pathology diagnoses. Conclusions The non-invasive differently expressed genes we have identified warrant future investigation towards the development of their potential in precision diagnostics and precision pan-disease immunotherapeutics.

[Do organizational barriers to pneumococcal and influenza vaccine access exist?]. / Existe-t-il des barrières organisationnelles à l'accessibilité à la vaccination contre l'influenza et le pneumocoque?

CONTEXT: Despite the implementation of a Quebec immunization program against influenza and pneumococcal disease (PQIIP), vaccine coverage has remained low. There have been many studies on personal barriers to vaccination, but few have explored other kinds of barriers. OBJECTIVES: To explore the presence of barriers in relation to the organization of the health care system and to propose recommendations for increasing vaccine coverage. METHODS: Within a mixed protocol, a phone survey of 996 people in the target population and a case study implicating the follow-up of the PQIIP with all the site and actor categories via 43 semistructured interviews and 4 focus groups were realized. Survey data underwent a descriptive statistical analysis. Qualitative analysis followed the Miles and Huberman approach. RESULTS: The results indicate the presence of barriers with regard to information accessibility. These include access to: the physicians' recommendation, knowledge of the efficacy or the security of vaccines, and admissibility of clients to the PQIIP. Organizational barriers were also found to limit access to vaccination, especially in terms of restricted choices of time and location. Coordination and incentives mechanisms are not optimal. Removal of organizational barriers depends more on strategic rather than structural factors. CONCLUSION: Addressing organizational barriers should be an important component of strategies aimed at improving vaccine coverage. Public health authorities should focus on strategic management of the information and inter-organizational environment.

Acute regulation of circulating parathyroid hormone (PTH) molecular forms by calcium: utility of PTH fragments/PTH(1-84) ratios derived from three generations of PTH assays.

CONTEXT: 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. OBJECTIVE: 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. DESIGN: 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. RESULTS: From hypo- to hypercalcemia, the C/CA ratio had the highest range (1.92 to 9.75; P < 0.001), and the C/T ratio had a higher range (1.69 to 6.11; P < 0.01) 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). CONCLUSIONS: 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.

Influence of Secondary Hyperparathyroidism Induced by Low Dietary Calcium, Vitamin D Deficiency, and Renal Failure on Circulating Rat PTH Molecular Forms.

Rats(r) with secondary hyperparathyroidism were studied to define the relationship between vitamin D metabolites and rPTH levels measured by 3 different rat ELISAs. Controls and renal failure (RF) rats were on a normal diet, while 2 groups on a low-calcium (-Ca) or a vitamin D-deficient (-D) diet. RF was induced surgically. Mild RF rats had normal calcium and 25(OH)D but reduced 1,25(OH)(2)D levels (P < .001) with a 2.5-fold increased in rPTH (P < .001). Severe RF rats and those on a -Ca or -D diet had reduced calcium (P < .01) and 25(OH)D levels (P < .05), with rPTH increased by 2 (-Ca diet; P < .05), 4 (-D diet; P < .001), and 20-folds (RF; P < .001) while 1,25(OH)(2)D was high (-Ca diet: P < .001) or low (-D diet, RF: P < .001). 25(OH)D and 1,25(OH)(2)D were positively and negatively related on the -Ca and -D diets, respectively. rPTH molecular forms behaved as expected in RF and on -Ca diet, but not on -D diet with more C-rPTH fragments when less were expected. This may be related to the short-time course of this study compared to prior studies.

An N-terminal molecular form of parathyroid hormone (PTH) distinct from hPTH(1 84) is overproduced in parathyroid carcinoma.

BACKGROUND: A new parathyroid hormone (PTH) species, the N-terminal PTH form (N-PTH), is distinct from intact human PTH of 84 amino acid residues [hPTH(1-84)] and is recognized in a 3rd-generation assay of "whole" PTH (wPTH; the 1-2 epitope) but not in a 2nd-generation assay of "total" PTH (tPTH; the 12-18 epitope). N-PTH usually represents <15% of wPTH but can be overproduced in severe primary hyperparathyroidism (PHPT) and secondary hyperparathyroidism. We investigated whether N-PTH is also overproduced in parathyroid cancer and whether N-PTH concentration is influenced by calcimimetic therapy. METHODS: We studied 8 patients with parathyroid carcinoma before and at week 16 of cinacalcet therapy, 6 patients with PHPT, and 6 control individuals. We fractionated sera with HPLC and analyzed fractions with the 2 assays to quantify hPTH(1-84), N-PTH, and non-(1-84) PTH fragments. RESULTS: Half of parathyroid carcinoma patients had an increased wPTH:tPTH ratio [mean (SD), 1.35 (0.29)]; the others had a typical ratio [0.72 (0.12)]. HPLC fractionation of sera from 2 high-ratio patients confirmed N-PTH overproduction [65% (12%) of wPTH]. The N-PTH fraction was <15% of wPTH in PHPT and healthy individuals. Calcimimetic therapy appreciably reduced calcium concentrations in parathyroid carcinoma patients but had little influence on PTH concentration, the wPTH:tPTH ratio, or the PTH HPLC profile. CONCLUSION: N-PTH is overproduced in some parathyroid cancer patients, but calcimimetic therapy does not influence its production. The clinical implications of this finding in parathyroid carcinoma await additional studies with an emphasis on N-PTH's biological activity and with larger numbers of patients.

Overproduction and secretion of a novel amino-terminal form of parathyroid hormone from a severe type of parathyroid hyperplasia in uremia.

Measurement of bioactive parathyroid hormone (PTH) is essential for optimal management of bone abnormalities in dialysis patients. This can be accomplished by PTH measurements using third-generation PTH assays, which detect more or less of the first six amino acids of the PTH structure. Such assays do not detect non-(1-84) PTH fragments, such as human PTH (7-84), which are recognized by the second-generation PTH assays that use a detection antibody that recognizes an epitope within the 13-34 region of the PTH structure. Therefore, third-generation PTH results are expected to be lower than those that are obtained with second-generation PTH assays. Rare exceptions to this rule have been reported for patients with severe primary hyperparathyroidism or parathyroid cancer. Sera and gland extracts were analyzed from a dialysis patient with high bone turnover disease and with surprising higher PTH levels by a third-generation assay than by a second-generation assay. This finding normalized after the surgical removal of an enlarged gland with a single nodule, an advanced type of nodular hyperplasia. HPLC fractionation of sera and gland extracts revealed the overproduction and secretion of a PTH molecule with an intact amino-terminus structure distinct from (1-84) PTH. This form of PTH was readily detectable by third-generation PTH assays but was poorly reactive in second-generation PTH assays. Therefore, parathyroid glands with advanced uremic nodular hyperplasia may overproduce and secrete a novel, biologically active form of PTH with an intact 1-6 region but a presumably modified 12-18 region required for the detection in second-generation PTH assays.

Evidence that the amino-terminal composition of non-(1-84) parathyroid hormone fragments starts before position 19.

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 [Tyr(34)]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 [Tyr(34)]hPTH(19-84) in various cell lines and in mouse osteocytes with PTH/PTHrP type I receptor ablation.

Overproduction of an amino-terminal form of PTH distinct from human PTH(1-84) in a case of severe primary hyperparathyroidism: influence of medical treatment and surgery.

OBJECTIVE: Rare patients with severe primary hyperparathyroidism present with large parathyroid tumours, severe hypercalcaemia, very high PTH levels and osteitis fibrosa cystica. Some of these patients display a large amount of C-PTH fragments in circulation and present with a higher C-PTH/I-PTH ratio than seen in less severe cases of primary hyperparathyroidism. We wanted to determine how PTH levels and circulating PTH high-performance liquid chromatography (HPLC) profiles analysed with PTH assays having different epitopes could be affected by medical and surgical treatment in such patients. DESIGN: A 55-year-old man with severe hypercalcaemia (Ca(2+): 2.01 mmol/l), very high PTH levels (CA-PTH 82.1 and T-PTH 72 pmol/l) caused by a large parathyroid tumour (7.35 g) and accompanied by significant bone involvement (alkaline phosphatase of 185 UI/l and subperiostal bone resorption of hands) was referred to us. Blood was obtained at various time points during his medical treatment, before and after surgery, to measure parameters of calcium and phosphorus metabolism, and of bone turnover. HPLC separations of circulating PTH molecular forms were performed and analysed with PTH assays having 1-4 (CA), 12-18 (T), 26-32 (E) and 65-84 (C) epitopes. RESULTS: Before surgery, serum Ca2+ was nearly normalized with hydratation, intravenous (IV) pamidronate and oral vitamin D administration. Despite a decrease in Ca2+ to 1.31 mmol/l, CA-PTH and T-PTH levels decreased by half in relation to a threefold increase in basal 1,25-dihydroxyvitamin D [1,25(OH)2D] level (94 to 337 pmol/l). After this initial positive response, hypercalcaemia and elevated CA- and T-PTH levels recurred even if 1,25(OH)2D levels remained elevated. The tumour was removed surgically and proved to be poorly differentiated with nuclear atypia and mitosis. After surgery, the Ca2+ level and PTH secretion normalized. The higher CA-PTH level relative to the T-PTH level observed before surgery in this patient was related to the oversecretion of an amino-terminal (N) form of PTH recognized by PTH assays with (1-4) or (26-32) epitopes but not by the T-PTH assay with a (12-18) epitope. This molecular form represented 50% of CA-PTH measured in this patient, but only 7% in less severe cases of primary hyperparathyroidism. It was unaffected by medical therapy and disappeared after surgery. CONCLUSION: The relationship between the overexpression of this N-PTH molecular form and severe primary hyperparathyroidism remains unclear. Further studies will be required in these rare patients to see whether N-PTH is a marker of less well differentiated parathyroid tumours and/or relates to the overproduction of C-PTH fragments in the presence of severe hypercalcaemia.

Structure of non-(1-84) PTH fragments secreted by parathyroid glands in primary and secondary hyperparathyroidism.

BACKGROUND: Non-(1-84) parathyroid hormone (PTH) fragments are large circulating carboxyl-terminal (C) fragments with a partially preserved amino-terminal (N) structure. hPTH (7-84), a synthetic surrogate, has been demonstrated to exert biologic effects in vivo and in vitro which are opposite to those of hPTH (1-34) on the PTH/PTHrP type I receptor through a C-PTH receptor. We wanted to determine the N structure of non-(1-84) PTH fragments. METHODS: Parathyroid cells isolated from glands obtained at surgery from three patients with primary hyperparathyroidism and three patients with secondary hyperparathyroidism were incubated with 35S-methionine to internally label their secretion products. Incubations were performed for 8 hours at the patient-ionized calcium concentration and in the presence of various protease inhibitors. The supernatant was fractionated by high-performance liquid chromatography (HPLC) and fractions were analyzed with PTH assays having (1 to 4) and (12 to 23) epitopes, respectively. The serum of each patient was similarly analyzed. Peaks of immunoreactivity identified were submitted to sequence analysis to recover the 35S-methionine residues in positions 8 and 18. RESULTS: Three regions of interest were identified with PTH assays. They corresponded to non-(1-84) PTH fragments (further divided in regions 3 and 4), a peak of N-PTH migrating in front of hPTH (1-84) (region 2) and a peak of immunoreactivity corresponding to the elution position of hPTH (1-84) (region 1). The last corresponded to a single sequence starting at position 1. Region 2 gave similar results in all cases (a major signal starting at position 1) but also sometimes minor sequences starting at position 4 or 7. Regions 3 and 4 always identified a major sequence starting at positions 7 and minor sequences starting at positions 8, 10, and 15. Surprisingly, a major signal starting at position 1 was also present in region 3. The HPLC profile obtained from a given patient's parathyroid cells was qualitatively similar to the one obtained with his/her serum in each case. CONCLUSION: These results indicate that non-(1-84) PTH fragments are composed of a family of fragments which may be generated by specific or progressive cleavage at the N region. The longest fragment starts at position 4 and the shortest at position 15. A peptide starting at position 7 appears as the major component of non-(1-84) PTH fragments. The generation process is similar to the one described for smaller C-PTH fragments a number of years ago, suggesting a similar production mechanism and source for all C-PTH fragments.

Amino-terminal form of parathyroid hormone (PTH) with immunologic similarities to hPTH(1-84) is overproduced in primary and secondary hyperparathyroidism.

BACKGROUND: To separate non-(1-84)parathyroid hormone [non-(1-84)PTH] from PTH(1-84), we developed new HPLC gradients and observed that the peak coeluting with hPTH(1-84) could be separated into two entities recognized by a cyclase-activating PTH (CA-PTH) assay that reacts with the first four amino acids of the PTH structure. METHODS: Sera from six healthy individuals and five patients with primary hyperparathyroidism, and eight pools of sera from patients in renal failure were fractionated by HPLC. A total (T)-PTH assay reacting with the (15-20) region, the CA-PTH assay, and a COOH-terminal (C)-PTH assay with a (65-84) structure requirement were used to measure basal and fractionated PTH values. RESULTS: T-PTH was higher than CA-PTH in all healthy controls [mean (SD), 3.13 (0.37) vs 2.29 (0.33) pmol/L; P <0.01] and in renal failure patients [47 (35.1) vs 33.4 (26.1) pmol/L; P <0.01]. By contrast, CA-PTH concentrations were similar to or higher than T-PTH in three of five patients with primary hyperparathyroidism [25.7 (26.1) vs 23.1 (24.2) pmol/L; not significant]. The CA-PTH assay reacted with the hPTH(1-84) peak and with a minor peak different from the non-(1-84) peak recognized by the T-PTH assay. This minor peak was not recognized by the T-PTH assay. It represented 8 (2)% of CA-PTH in controls, 25 (23)% in patients with primary hyperparathyroidism, and 22 (7)% in renal failure patients, assuming equimolar reactivity to hPTH(1-84) in the CA-PTH assay. It was not oxidized hPTH(1-84), which migrated differently on HPLC and reacted similarly in the CA and T-PTH assays. CONCLUSIONS: This new molecular form of PTH has structural integrity of the (1-4) region but presumably is modified in the region (15-20), which is usually recognized by the T-PTH assay. Its clinical implications remain to be defined.