Primary hyperparathyroidism and the presence of kidney stones are associated with different haplotypes of the calcium-sensing receptor.

INTRODUCTION: Three single-nucleotide polymorphisms in the calcium-sensing receptor gene (CASR) encoding the missense substitutions A986S, R990G, and Q1011E have been associated with normal variation in extracellular calcium homeostasis, both individually and in haplotype combination. The aim of this study was to examine haplotype associations in primary hyperparathyroidism (PHPT). PATIENTS AND METHODS: Patients with sporadic PHPT (n = 237) were recruited from endocrine clinics and healthy controls (n = 433) from a blood donor clinic, and levels of serum calcium, albumin, and PTH were measured. In PHPT patients, urinary calcium/creatinine clearances and bone mineral density at spine and femoral neck were measured and the presence of kidney stones and vertebral fractures identified. The CASR single-nucleotide polymorphisms were haplotyped by allele-specific sequencing. RESULTS: Four haplotypes (ARQ, SRQ, AGQ, and ARE) of eight were observed, in keeping with significant linkage disequilibrium, but haplotype frequencies did not show significant Hardy-Weinberg disequilibrium. The SRQ haplotype was more common in PHPT (125 of 474 alleles) than in controls (170 of 866 alleles, P = 0.006) and showed a significant (P = 0.006) gene-dosage effect. There was no significant association between haplotype and bone mineral density or fractures, but association with kidney stones was significant (P = 0.0007). In the stone-forming subgroup, the SRQ haplotype was underrepresented and AGQ overrepresented. Patients bearing the AGQ haplotype had an odds ratio of 3.8 (95% confidence interval, 1.30-11.3) for presentation with renal stones compared with the rest. CONCLUSION: Our data indicate that the CASR SRQ haplotype is significantly associated with PHPT in our population. Within the PHPT patient population, the AGQ haplotype is significantly associated with kidney stones.

The risk of fractures in postmenopausal women with primary hyperparathyroidism.

OBJECTIVE: To evaluate the prevalence of vertebral (vFr) and non-vertebral (nvFr) fractures in postmenopausal women with primary hyperparathyroidism (PHPT). MATERIALS AND METHODS: We studied 98 patients with PHPT, divided into 'mild' (M, n = 25) and 'non-mild' (NM, n = 73) sub-groups, according to recently published guidelines (2002), and 89 healthy women (C) matched for age, years since menopause and body mass index. vFr was evaluated according to a visual semiquantitative method; bone mineral density (BMD) at the lumbar spine (LS), and femoral sites (femoral neck, FN and total femur, FT) was measured by dual energy X-ray absorptiometry. Volumetric BMD of the third lumbar vertebra (vBMDL3) was also calculated. RESULTS: The prevalence of vFr was significantly higher (P < 0.001) in both M and NM PHPT patients compared with C; this prevalence did not differ between M and NM patients. BMD was significantly lower (P < 0.05) in NM patients compared with both C and M patients. BMD at LS in M patients was also significantly higher with respect to C. Similar results were also obtained for vBMDL3; in M patients, vBMDL3 was also significantly higher compared to C. When M and NM patients were subdivided according to the presence or lack of vFr, no difference was found between fractured and unfractured patients for either BMD or vBMDL3 values. CONCLUSIONS: The risk of vFr is higher in postmenopausal patients with mild PHPT even if BMD appears well preserved. This finding suggests that other factors, such as bone quality, seem to be relevant in determining fracture risk, especially when gonadal function is lacking.

Vitamin D status as the major factor determining the circulating levels of parathyroid hormone: a study in normal subjects.

We investigated the relative contribution of the major factors regulating calcium homeostasis in determining the circulating levels of PTH. We studied 137 males and 125 females who were healthy volunteers. Circulating PTH levels were determined by three different immunoradiometric assays (IRMA). The first one (PTH Sorin, PTH S) utilizes two affinity-purified polyclonal antibodies directed against the 1-34 and 39-84 sequence of the hormone. The two other IRMA share polyclonal anti-PTH (39-84) antibodies. The first assay (PTH Whole, PTH W) utilizes a second polyclonal antibody, directed against the 1-4 amino acid sequence. The second assay (PTH Total, PTH T) utilizes a second antibody specific for the 7-34 region. Concentrations of PTH fragments lacking the initial amino acid sequence (PTH N-truncated, PTH N-t) were determined by the difference of values between PTH T and PTH W. Vitamin D was the main explicative variable almost in every multiple linear regression model, both considering the group as a whole (PTH S: R2 = 0.238, P < 0.0001; PTH W: R2 = 0.08, P < 0.001; PTH T: R2 = 0.145, P < 0.0001; PTH N-t: R2 = 0.081, P < 0.009) and when considering men and women separately. In subjects with vitamin D insufficiency (n = 53) [25(OH)D < 30 nmol/l], mean serum levels of parathyroid hormone were significantly higher (P < 0.001) than those in subjects of similar age with normal vitamin status (n = 209) with all the assays employed. This study demonstrates the central role of 25(OH)D in regulating PTH secretion in physiological conditions.

Blood ionized calcium is associated with clustered polymorphisms in the carboxyl-terminal tail of the calcium-sensing receptor.

Blood ionized calcium (iCa) is a quantitative trait subject to genetic influence. iCa is maintained in a narrow range through the action of the calcium-sensing receptor (CASR) controlling PTH secretion and calcium excretion. A CASR single nucleotide polymorphism (SNP) prevalent in Caucasian populations (A986S) has shown significant association with iCa in a cohort of young women, but association with the neighboring SNPs, R990G and Q1011E, has not been examined. We studied 377 unrelated adults (184 men and 193 women) recruited as healthy adults from a blood donor clinic. The subjects were not taking any medications, nor did they have disorders of calcium metabolism. Relative frequencies for the CASR 986S, 990G, and 1011E minor alleles were 24%, 4%, and 3% respectively. At the A986S locus, subjects with the AA genotype had significantly lower iCa (P = 0.0001) than subjects with one or two S alleles (mean +/- se, 1.221 +/- 0.003 vs. 1.239 +/- 0.003 mmol/liter). For the R990G site, subjects with the RR genotype had higher iCa than those with one copy of the 990G allele (1.230 +/- 0.002 vs. 1.213 +/- 0.007 mmol/liter; P = 0.032). With respect to the 1011 locus, iCa was lower in QQ genotype subjects than in the QE group (1.227 +/- 0.002 vs. 1.255 +/- 0.008 mmol/liter; P = 0.002). After resolution of phase for the doubly heterozygous subjects, analysis was conducted on haplotypes across all three loci. As expected, subjects with SRQ and ARE haplotypes are relatively hypercalcemic, and those with AGQ are hypocalcemic, relative to subjects with the common ARQ haplotype. Multiple regression analysis with clinical covariates (age, sex and menopausal status, creatinine, and PTH) showed that 16.5% of the total variance in iCa may be explained, and the seven CASR haplotypes contribute significantly (P < 0.0001) and substantially (49.1% of the explained variance) to the model, with the following corrected iCa means: ARQ/AGQ, 1.21 +/- 0.01; ARQ/ARQ, 1.22 +/- 0.01; ARQ/SRQ, 1.24 +/- 0.01; SRQ/AGQ, 1.24 +/- 0.03; SRQ/SRQ, 1.25 +/- 0.01; ARQ/ARE, 1.25 +/- 0.01; and SRQ/ARE, 1.27 +/- 0.01. Our data confirm the association between iCa and the A986S locus and suggest that R990G and Q1011E are also predictive. Given the significant between-population variations in frequency of variant alleles in this CASR SNP cluster, tri-locus haplotyping may prove to be more informative in studies of association between variation in CASR and disease.

Quality of life in ambulatory postmenopausal women: the impact of reduced bone mineral density and subclinical vertebral fractures.

Health-related quality of life (HRQOL) in postmenopausal women with osteoporosis has hitherto been mainly assessed in patients with clinically recognized vertebral fractures. Our study aimed to investigate the QOL perception in 361 asymptomatic ambulant postmenopausal women who came to our center for an osteoporosis screening program planned with their general practitioners. The Quality of Life Questionnaire of the European Foundation for Osteoporosis (QUALEFFO) was administered to all subjects. The participants underwent bone mineral density (BMD) measurements by DXA of either the lumbar spine and/or the femoral neck, as well as X-ray examination of the thoracolumbar spine to identify subclinical vertebral fractures. According to the WHO definition, where subjects are subdivided by BMD values into three groups (women with normal BMD, osteopenia, and osteoporosis), a significant difference was found only for the domains which explore general health perception (p<0.01 by ANOVA) and mental function (p<0.001 by ANOVA). When we segregated both osteopenic and osteoporotic women according to whether or not they had vertebral fractures, a significant difference was found only in osteoporotic patients for domains which explore physical function (p<0.001), social function (p<0.001), general health perception (p<0.02), and total QUALEFFO score (p<0.01). Stepwise multiple logistic regression analysis of the whole sample showed that both vertebral fractures and a low femoral BMD impairs QOL perception, while age did not exert a significant influence. ROC curves analysis demonstrated a low discriminating capacity of individual domains and total QUALEFFO score for both vertebral deformities and BMD categorization. Our results showed that QUALEFFO is not able to discriminate between patients with or without subclinical vertebral fractures. However, some aspects of QOL appear to be impaired in patients with subclinical vertebral fractures or reduced BMD.

Potential clinical utility of a new IRMA for parathyroid hormone in postmenopausal patients with primary hyperparathyroidism.

BACKGROUND: A new commercially available (so-called second-generation) IRMA for parathyroid hormone (PTH) separately detects intact PTH and its N-truncated fragments; however, no studies have compared the first- and second-generation IRMAs for PTH in patients with primary hyperparathyroidism (PHPT) to assess their respective diagnostic accuracies. METHODS: We concomitantly investigated 39 postmenopausal patients with PHPT and a control group of 70 healthy postmenopausal women matched for age, renal function, and vitamin D status. In all individuals, PTH was measured with a classic IRMA (PTH-S; DiaSorin Inc.), which uses antibodies directed against epitopes 1-34 and 39-84, and a new method (Scantibodies Laboratory. Inc.), which uses antibodies against epitopes 1-4 and 39-84 (PTH-W) and epitopes 7-34 and 39-84 (PTH-T). We also assayed serum PTH in 10 PHPT patients every 24 h for 5 days after successful surgery. RESULTS: The different assays gave serum PTH values that were >2 SD higher than values for the control population in 59% (PTH-S), 77% (PTH-W), and 82% (PTH-T) of patients with PHPT. However, ROC curve analysis showed no significant differences among the three PTH assays, demonstrating overlapping diagnostic sensitivities. In PHPT patients, the correlation among the assays was highly significant (r = 0.91-0.92; P <0.001). The ratio PTH-W:PTH-T x 100 showed a gaussian distribution in both PHPT patients and controls, whose mean (SD) values [63.4 (13.3)% vs 64.5 (9.5)%, respectively] did not differ significantly. After parathyroidectomy, the mean percentages of variation in PTH detected with all of the assays were quite similar. CONCLUSIONS: The distribution of the PTH-W:PTH-T ratio in patients and controls suggests that PHPT does not markedly influence the rate at which biologically inactive fragments are generated by central or peripheral cleavage of PTH. The similar postoperative curves seem to contradict the hypothesized effect of acute hypocalcemia in modulating the central secretion of hormonal fragments. Our results indicate that the three investigated assays have similar diagnostic sensitivities in PHPT.

Vitamin D status in female patients with primary hyperparathyroidism: does it play a role in skeletal damage?

OBJECTIVE: Vitamin D deficiency, even subclinical, has been considered to worsen the skeletal damage in primary hyperparathyroidism (PHPT). Our study aimed to investigate the impact of vitamin D status on skeletal involvement in PHPT. DESIGN AND MEASUREMENTS: A cross-sectional study was designed involving 62 female patients with PHPT. Serum total calcium (tCa), phosphate (P), creatinine (Cr) and total alkaline phosphatase activity (AP), together with 24-h (uCa 24 h) and spot fasting (uCa/Cr) urinary calcium, were measured by autoanalyser; ionized calcium (iCa) was assessed by an ion-specific electrode; intact parathyroid hormone (PTH) was measured by immunoradiometric assay (IRMA) and 25-hydroxyvitamin D (25-OHD) by radioimmunoassay (RIA). Bone mineral density (BMD) was measured by dual energy X-ray absorptiometry (DXA) at lumbar spine in 58 patients, and at femoral neck, Ward's triangle, greater trochanter, intertrochanteric line and total hip in 56 patients. The associations of all variables with age, 25-OHD, body mass index (BMI) and PTH were studied by linear multiple regression analysis, using progressively restricted models. RESULTS: The model including age, 25-OHD, PTH and BMI showed significant regression with BMD values. PTH, age and BMI exerted a leading role in determining such a significance, while no significant regression was found between the parameters studied and 25-OHD; this was confirmed by Pearson's linear correlation analysis. The progressively restricted models showed significant regression of BMD at femoral neck, femoral intertrochanteric line and total hip with age, BMI and PTH. BMD measured at the Ward's triangle and greater trochanter showed significant regression with age and BMI, and that measured at lumbar spine with age. CONCLUSIONS: Our data indicate that in primary hyperparathyroidism patients the influence of 25-hydroxyvitamin D levels on bone mineral density, if any, was overwhelmed by the effects of parathyroid hormone excess, age and body mass index. The latter unequally affected bone mineral density of various measured sites with different composition.

Impact of fractures on health care in a major university hospital in Rome.

BACKGROUND AND AIMS: The aim of the study was to investigate the impact of fractures (i.e., hip, Colles, humeral and vertebral fractures), compared with that of other common diseases requiring hospitalization, on health care in the main hospital in Rome (Italy). METHODS: Hospital discharge forms, filled in according to the 9th International Classification of Diseases, were examined from 1996 to 1999. Data on fractures were compared with those related to other diseases which occupy a considerable proportion of hospital operating time in Italy: coronary heart disease (CHD), cerebrovascular disorders (CVD), diabetes mellitus (DM), chronic obstructive pulmonary disease (COPD) and breast cancer (BC). RESULTS: In all groups of patients, the mean age of females was significantly higher (p<0.0001) than that of males. Male patients with hip fractures had hospital stays significantly longer than females (p<0.0001), whereas women with Colles fractures had significantly (p<0.02) longer stays. When patients were divided according to age (i.e., over or under 60 years), mean hospital stays did not differ between younger and older patients in all groups except Colles fractures (p<0.001). Hip fractures in older patients showed striking in-hospital mortality. Throughout the study period, hip fractures accounted for the highest overall and per-patient costs. The number of female patients with fractures (and, obviously, breast cancer) was higher, while the opposite applied to the other disorders. Male patients with fractures, CHD and CVD were significantly younger than females (p<0.0001). When the percentage of deaths was added to that of patients discharged to other institutions, fractures showed the poorest outcome of any hospitalization event. Per-patient costs were remarkably higher for CHD, followed by fractures. CONCLUSIONS: Fractures represent a growing but often underestimated burden for hospital care in Italy; further studies are needed on this issue.

[Clinical aspects of osteoporosis]. / Gli aspetti clinici dell'osteoporosi.

The main clinical presentation of osteoporosis is fracture and its consequences. However a number of diseases and factors can induce bone loss and increase the risk of fracture. Therefore the clinical approach should be initially directed to exclude secondary osteoporosis. Vertebral fractures are the most common osteoporotic fractures; they are characterized by back pain, typical physical changes such as kyphosis and height loss, functional impairment and social decline. On the other hand, hip fracture is the most severe consequence of osteoporosis, because of its higher morbility and mortality. The main pathogenetic determinants of hip fracture are represented by both bone loss and several factors contributing to fall in the elderly. Moreover, a number of conditions are responsible for the high mortality rate following hip fracture. Colles' fracture is rarely hospitalized; however, most patients complain a complex algodystrophic syndrome which impairs the quality of life.

Concurrent parathyroid adenomas and carcinoma in the setting of multiple endocrine neoplasia type 1: presentation as hypercalcemic crisis.

We describe a patient with multiple endocrine neoplasia type 1 characterized by the simultaneous occurrence of parathyroid cancer, parathyroid adenomas, and pancreatic gastrinoma, who presented with an episode of acute hypercalcemia. The rapid parathyroid hormone assay provided a basis for the diagnosis of parathyroid hyperfunction. Mediastinal metastasis of the parathyroid carcinoma was found at autopsy. However, the staining of pancreatic and gastric tissue for parathyroid hormone-related protein does not make it possible to exclude completely the contribution of this peptide in mediating the hypercalcemia. To our knowledge, this is the first reported case of parathyroid carcinoma as part of the multiple endocrine neoplasia type 1 syndrome.