Suppression of parathyroid hormone secretion with oral calcium in normal subjects and patients with primary hyperparathyroidism

Comparison of Normocalcemic vs Hypercalcemic Primary Hyperparathyroidism in a Hypercalciuric Renal Stone Population

CONTEXT

Primary hyperparathyroidism (PHPT) is commonly diagnosed in the setting of hypercalcemia, whereas normocalcemic primary hyperparathyroidism (NHPT) may be misdiagnosed.

OBJECTIVE

Our objective was to compare patients with hypercalcemic hyperparathyroidism (HPHPT) vs patients with NHPT hypercalciuric renal stones.

METHODS

We took advantage of a routine calcium load test performed in patients with hypercalciuric renal stones to assess retrospectively among patients with PHPT the prevalence and characteristics of NHPT and HPHPT under a calcium-restricted diet.

RESULTS

Among 1671 patients with hypercalciuria, 91 patients had a final diagnosis of PHPT (postload ionized calcium [iCa] > 1.31 mmol/L and parathyroid hormone [PTH] > 30 pg/mL). Prevalence of NHPT is 40% of all PHPT; however, according to total serum calcium, 4/35 NHPT and 7/56 HPHPT cases would have been misclassified in the other group. Eighteen of 35 NHPT and 40/56 HPHPT cases underwent parathyroidectomy. No significant characteristics relating to parathyroid weight, stone composition, or bone remodeling biomarkers were detected between groups. Although iCa is higher in HPHPT in the fasting state and after calcium load, we found no difference for calcium diet, 24-hour calciuria, or calcitriol. Renal calcium excretion postload increased by 303% in NHPT but only 176% in HPHPT (P = .01) likely explained by a lesser PTH decrease (P = .02). However, a strong negative association (P < .0001) detected between pooled preload and postload iCa and PTH only in the NHPT group suggests a persistent efficient PTH-CaSR control within the parathyroid glands in this group.

CONCLUSION

Our data show the relevance of dynamic tests to unmask NHPT in patients with hypercalciuric renal stones.

The Eucalcemic Patient With Elevated Parathyroid Hormone Levels

Primary hyperparathyroidism (PHPT) is classically characterized by hypercalcemia with elevated or inappropriately normal parathyroid hormone (PTH) levels. Elevated PTH levels in the presence of normal calcium levels are not infrequently found during the evaluation of metabolic bone disorders or kidney stone disease. This can be caused by secondary hyperparathyroidism (SHPT) or normocalcemic primary hyperparathyroidism (NPHPT). NPHPT is due to autonomous parathyroid function whereas SHPT is caused by a physiologic stimulation to PTH secretion. Many medical conditions and medications can contribute to SHPT, and differentiation between SHPT and NPHPT may be difficult. Cases are presented to illustrate examples. In this paper, we review the distinction between SHPT and NPHPT as well as end organ effects of NPHPT and outcomes of surgery in NPHPT. We suggest that the diagnosis of NPHPT be made only after careful exclusion of causes of SHPT and consideration of medications that can increase PTH secretion. Further, we advise a conservative approach to surgery in NPHPT.

Salivary calcium as a diagnostic tool for screening of osteoporosis in postmenopausal women

Background

Women's health undergoes physiological, pathological and psychological changes after menopause. Reduced estrogen levels have been implicated in the pathogenesis of osteoporosis in postmenopausal women. Estrogen is also known to affect the salivary gland functions. To understand the association between serum estrogen, osteoporosis and salivary calcium, the present cross-sectional study was undertaken.

Aim

The aim of this study is to determine salivary calcium levels and its use for the diagnosis of osteoporosis in postmenopausal women.

Methodology

Ninety individuals divided into three groups of healthy controls, pregnant women and postmenopausal women were selected. Serum estrogen, salivary calcium and bone mineral density (BMD) at the heel region were estimated. Statistical analysis using the Mann-Whitney U-test was done to compare the results within the groups.

Results

Mean estrogen levels were 115.8 ± 80.18 pg/mmol in control group, 7729.4 ± 907.6 pg/mmol in pregnant group and 51.2 ± 74.51 pg/mmol in postmenopausal group, respectively. The mean salivary calcium in control, pregnant and postmenopausal groups was 3.12 ± 0.63, 3.19 ± 0.62 and 7.12 ± 0.79 μg/dl, respectively. Paired comparison within the groups showed high statistical significance (P = 0.0000) in the salivary calcium levels. The mean BMD of -2.3 (standard deviation [SD] ± 0.83) in the postmenopausal group was significantly lower than -0.6 (SD ± 0.99) and -0.2 (SD ± 1.42) of pregnant and control groups, respectively.

Conclusion

A negative correlation was found between estrogen and bone density. A significant difference in salivary calcium was noted in the study groups, highlighting the role of salivary calcium in the detection of early bone changes in postmenopausal women.

Clinical characteristics and depression score response after parathyroidectomy in primary hyperparathyroidism

OBJECTIVE

Several studies indicate that patients with primary hyperparathyroidism (PHPT) undergoing parathyroid surgery have improvement in mood and neuropsychological functioning. The current analysis aims to examine the relationship between biochemical and clinical variables and the improvement in depression scores and in specific symptoms, after parathyroidectomy.

DESIGN

A prospective observational case-control study at a referral centre.

PATIENTS

Patients with PHPT undergoing parathyroidectomy (n = 88) or thyroid surgery (n = 85).

MEASUREMENTS

The Patient Health Questionnaire-9 (PHQ-9) was utilized to obtain depression scores at enrolment and 12 months after surgery. The changes in PHQ-9 were analysed and correlated with baseline clinical and biochemical parameters.

RESULTS

At enrolment, there was no difference between the groups in the number with a depression diagnosis (PHPT 34.1%, thyroid surgery, 35.5%, P = 0.86). However, baseline PHQ-9 scores were significantly higher in PHPT (median 7.5, range 0-27) than thyroid surgery patients (median 3.0, range 0-18, P < 0.0001). Following surgery, all PHQ-9 scores, total and symptom group (cognitive, somatic) improved and were no longer different between PHPT (total PHQ-9 median 2, range 0-16) and thyroid (median 1, range 0-14, P = 0.31) groups. Baseline parathyroid hormone level, but not calcium, had a weak relationship with change in PHQ-9 score after parathyroid surgery (P = 0.003). Baseline PHQ-9 score was correlated with change in PHQ-9 score at 12 months after parathyroid surgery (P < 0.001).

CONCLUSIONS

Depression scores improve in both somatic and cognitive domains after parathyroidectomy for PHPT and baseline severity of depression predicts the response.

Response to the Boucher et al. Comments on Fleury et al. Sun Exposure and Its Effects on Human Health: Mechanisms through Which Sun Exposure Could Reduce the Risk of Developing Obesity and Cardiometabolic Dysfunction. Int. J. Environ. Res. Public Health 2016, 13, 999

We thank Boucher et al. [1] for their interest in our recently published review [2]. [...].

Thiazide-Associated Hypercalcemia: Incidence and Association With Primary Hyperparathyroidism Over Two Decades

CONTEXT

Thiazide diuretics, the antihypertensive agent prescribed most frequently worldwide, are commonly associated with hypercalcemia. However, the epidemiology and clinical features are poorly understood.

OBJECTIVE

To update the incidence of thiazide-associated hypercalcemia and clarify its clinical features.

PATIENTS AND METHODS

In a population-based descriptive study, Olmsted County, Minnesota, residents with thiazide-associated hypercalcemia were identified through the Rochester Epidemiology Project and the Mayo Clinic Laboratory Information System from 2002-2010 and were added to the historical cohort beginning in 1992.

MAIN OUTCOME

Incidence rates were adjusted to the 2010 United States white population.

RESULTS

Overall, 221 Olmsted County residents were identified with thiazide-associated hypercalcemia an average of 5.2 years after initiation of treatment. Subjects were older (mean age, 67 years) and primarily women (86.4%). The incidence of thiazide-associated hypercalcemia increased after 1997 and peaked in 2006 with an annual incidence of 20 per 100,000, compared to an overall rate of 12 per 100,000 in 1992-2010. Severe hypercalcemia was not observed in the cohort despite continuation of thiazide treatment in 62.4%. Of patients discontinuing thiazides, 71% continued to have hypercalcemia. Primary hyperparathyroidism was diagnosed in 53 patients (24%), including five patients who underwent parathyroidectomy without thiazide discontinuation.

CONCLUSIONS

Many patients with thiazide-associated hypercalcemia have underlying primary hyperparathyroidism. Additionally, a sharp rise in thiazide-associated hypercalcemia incidence began in 1998, paralleling the increase observed in primary hyperparathyroidism in this community. Case ascertainment bias from targeted osteoporosis screening is the most likely explanation.

Secular trends in the incidence of primary hyperparathyroidism over five decades (1965-2010)

Introduction of automated serum calcium measurements in the 1970s resulted in a sharp rise in primary hyperparathyroidism (PHPT) incidence. However, recent investigations suggest a significant rise in PHPT incidence for unclear reasons. Our objective was to update our population-based secular trends in PHPT incidence, to determine if there has been a significant rise in PHPT incidence as suggested by others, and, if possible, to identify changes in clinical practice that might be responsible. Rochester, Minnesota, residents who met the criteria for PHPT from 2002 through 2010 were identified through the medical records-linkage system of the Rochester Epidemiology Project and added to the historical cohort beginning in 1965. Incidence rates were adjusted to the 2010 US white population. Altogether, 1142 Rochester residents have been diagnosed with PHPT since 1965, including 341 in 2002-2010. Over time, two periods of increased PHPT incidence occurred, one beginning in 1974 (121.7 per 100,000 person-years) and a second peak (86.2 per 100,000 person-years) starting in 1998. The median age of PHPT subjects has increased significantly from 55 years in 1985-1997 to 60 years of age in 1998-2010 and more patients (36%) had a parathyroidectomy in 1998-2010. Although serum calcium measurement has declined since 1996, there was a progressive increase in parathyroid hormone testing between 1994 and 2008. There was also a rise in orders for bone mineral density measurements in women since 1998, which peaked in 2003-2004. A second sharp rise in PHPT incidence occurred in our community in 1998, simultaneously with the introduction of national osteoporosis screening guidelines, Medicare coverage for bone density measurement, and new medications for the treatment of osteoporosis. Case ascertainment bias from targeted PHPT screening in patients being evaluated for osteoporosis is the most likely explanation.

Unstimulated whole saliva 25-hydroxycholecalciferol in patients with xerostomia in menopausal women

BACKGROUND AND AIM

The aim of this study was to compare unstimulated whole saliva 25-hydroxycholecalciferol (25(OH)D) in menopausal women with and without oral dryness (OD) feeling, and evaluate the relationship between saliva 25(OH)D and severity of OD feeling.

METHODS

A case-control study was carried out on 70 selected menopausal women aged 41-77 years with or without OD feeling (35 as case and 35 as control) conducted at the Clinic of Oral Medicine, Tehran University of Medical Sciences. Unstimulated saliva samples were obtained by expectoration. Xerostomia inventory (XI) score was used as an index of OD feeling severity. The saliva 25(OH)D concentration was measured by ELISA. Statistical analysis of Student's t test and Spearman correlation was used.

RESULTS

The mean saliva 25(OH)D level was significantly higher in the case group (897.1 ± 128.9 pg/ml), compared with control (156.7 ± 43.4 pg/ml; P < 0.05). XI score correlated significantly with saliva 25(OH)D concentration (r = 0.457, P < 0.001).

CONCLUSIONS

It seems that the level of salivary 25(OH)D concentration may be higher in menopausal women with OD feeling than in the control group, and there is a positive correlation between OD feeling severity and unstimulated whole saliva 25(OH)D.

Serum and saliva magnesium in postmenopausal women with xerostomia

OBJECTIVES

The aim of this study was to investigate serum, stimulated and unstimulated salivary magnesium in postmenopausal women with xerostomia.

MATERIALS

A case-control study was carried out on 60 selected postmenopausal women aged 41-77 years with or without xerostomia (30 as cases with xerostomia and 30 as controls without xerostomia), conducted at the Clinic of Oral Medicine, Tehran University of Medical Sciences. Unstimulated and paraffin-stimulated saliva samples were obtained by expectoration. Magnesium concentration was determined by the spectrophotometer method. Statistical analysis was carried out using Student's t-test.

RESULTS

The mean serum concentration, but not stimulated and unstimulated whole saliva magnesium concentrations, was significantly higher in the cases than in the controls.

CONCLUSION

Serum magnesium level appears to be associated with xerostomia in menopause.

Unstimulated whole saliva parathyroid hormone in postmenopausal women with xerostomia

OBJECTIVE

The aim of this study was to evaluate the correlation of xerostomia severity with unstimulated saliva parathyroid hormone (PTH) and to compare unstimulated whole saliva PTH between postmenopausal women with/without xerostomia.

METHODS

A case-control study was carried out in 60 (30 as case and 30 as control) selected postmenopausal women with/ without xerostomia conducted at the Clinic of Oral Medicine, Tehran University of Medical Sciences. Xerostomia inventory (XI) score was also used as an index of xerostomia severity. PTH concentration was analyzed by enzyme-linked immunosorbent assay (ELISA). Statistical analysis of Student's t-test and Spearman correlation was used.

RESULTS

The mean unstimulated saliva PTH concentration was significantly higher but flow rate was lower in the case group compared with control. XI score correlated significantly with saliva PTH (r = 0.688, p = 0.001) and flow rate (r = - 0.529, p = 0.001).

CONCLUSION

Xerostomia severity correlated positively with unstimulated whole saliva PTH and negatively with saliva flow rate in this group of postmenopausal women. Thus, salivary flow rate and PTH levels appear associated with xerostomia and menopause.

CLINICAL SIGNIFICANCE

Salivary PTH level appears to be associated with xerostomia and menopause.

Serum and stimulated whole saliva parathyroid hormone in menopausal women with oral dry feeling

OBJECTIVE

The aim of this study was to evaluate the correlation of severity of oral dryness (OD) with serum and saliva parathyroid hormone (PTH) and calcium levels, and to compare serum and stimulated whole saliva PTH and calcium between menopausal women with/without OD.

METHODS

A case-control study was carried out in 76 (38 as case and 38 as control) selected menopausal women with/without OD conducted at the Clinic of Oral Medicine, Tehran University of Medical Sciences (TUMS). Xerostomia Inventory (XI) score was also used as an index of OD severity. Serum and saliva Ca(+2) concentrations were assessed colorimetrically by Arsenazo reaction. PTH concentration was analyzed by enzyme-linked immunosorbent assay (ELISA). Statistical analysis of Student t test and Spearman correlation was used.

RESULTS

The mean saliva calcium and PTH concentrations and outputs, and serum PTH were significantly higher in the case group, compared with control. However, there were no significant differences in serum calcium concentration and stimulated saliva flow rate between groups. XI score correlated significantly with serum PTH (r = 0.387, P = .004), saliva concentration (r = 0.382, P = .002) and output (r = 0.346, P = .007) of PTH; and also with saliva concentration (r = 0.326, P = .013) and output (r = 0.315, P = .018) of calcium; but not with serum calcium and saliva flow rate.

CONCLUSION

OD severity correlated positively with serum and stimulated whole saliva PTH, and with saliva calcium levels in this group of menopausal women. Thus, salivary calcium and PTH levels appear associated with OD and menopause.

Primary hyperparathyroidism: role of the preoperative oral calcium loading test in the differential diagnosis between adenoma and hyperplasia

Whereas the sensitivity of the membrane calcium receptors is decreased in parathyroid adenoma, extracellular calcium may reduce parathyroid hormone (PTH) secretion through the protein kinase C pathway in parathyroid hyperplasia. The aim of this study was to determine the role of a preoperative oral calcium loading test in the differential diagnosis between adenoma and hyperplasia. Twenty-two subjects with adenoma (group A, age +/- standard error 56 +/-2 years, female/male 15/7), 10 individuals with hyperplasia (group H, age 54 +/-3, female/male 8/2), and 32 age and gender pair-matched controls (group C) underwent the test. Calcium and PTH were measured before and 60, 120, and 180 min after oral administration of 1 g of calcium (as gluconolactate). Product P was defined as minimal PTH concentration (pg/mL) x maximal calcium concentration (mg/dL) during the test. Ratio R was defined as relative PTH decline/relative calcium increase. The PTH decline during the test in group H was comparable to that of the controls. PTH decline <30%, Product P > 1,100, and Ratio R < 4 diagnosed adenoma with specificity of 100%, 90%, and 100%, respectively. PTH decline >60% diagnosed hyperplasia with specificity of 100%. The total accuracy of the test (65%) was comparable to that of technetium-99 m sestamibi scintigraphy (66%) and better than that of ultrasonography (58%). The test may discriminate patients with sporadic diffuse hyperplasia from individuals with solitary adenoma in cases of primary hyperparathyroidism with an indication for surgery.

Ultrastructural and histomorphometric alterations of rat jaw bones after experimental induction of lathyrism

OBJECTIVE

The aim of this study was to investigate the effect of beta-aminopropionitrile (beta-APN), present in Lathyrus sativus (L. sativus) seeds consumed in drought prone areas, on the maxillary and mandibular bones of rats.

DESIGN

Eighteen rats were used; they were divided into experimental group (12 rats) and a control group (6 rats). In the experimental group, lathyrism was induced by a once daily subcutaneous administration of beta-APN at a dose of 5mg in 0.4ml distilled water per 100g of body weight for 40 days. The specimens were examined histologically, histomorphometrically and ultrastructurally.

RESULTS

Histopathological examination of lathyritic rats showed that both mandible and maxillae were significantly affected. Irregular bone trabeculae with wide medullary cavities and abundant marrow spaces were observed. Focal resorptive areas lined with osteoclasts were also present. Histomorphometric analysis showed a decrease in the area percentage of bone in lathyritic rats as compared to the control. This decrease was statistically significant only in the mandible (p=0.018). Moreover, a significant increase in the number of osteoclasts (p=0.014, 0.012) and resorptive bays (p=0.013, 0.002) was detected in the maxillae and mandible of the experimental group, respectively. Ultrastructurally, there was a significant difference in the microarchitecture of the collagen fibres in lathyritic rats compared to the control. The collagen fibres in the lathyritic group appeared disorganized, fewer in number and more spaced.

CONCLUSIONS

This study provided evidence for lathyritic disturbances in bone architecture. These disturbances are likely to affect mineralization and bone strength as well.

Stimulated whole salivary flow rate and composition in menopausal women with oral dryness feeling

The aim of this study was to compare stimulated whole saliva flow rate and composition of menopausal women with/without oral dryness (OD) feeling. A case-control study was carried out in 42 selected menopausal women aged 52-73 years with or without OD feeling (21 as case and 21 as control) conducted at the Clinic of Oral Medicine, Tehran University of Medical Sciences. Paraffin-stimulated saliva samples were obtained by expectoration. The stimulated whole saliva composition was measured by a spectrophotometer [magnesium (Mg(+2)), calcium (Ca(+2)), chloride (Cl(-)), inorganic phosphate (Pi) and total protein], flame-photometry [sodium (Na(+))] and ion selective electrode (ISE) [potassium (K(+))] methods. No significant differences were found in stimulated whole saliva flow rate, Mg(+2), Cl(-), Pi, Na(+), K(+) and total protein concentrations between the two groups, but the mean calcium concentration was significantly higher in cases than in controls (P = 0.003). It seems that the level of salivary calcium concentration may be higher in menopausal women with OD feeling than in the control group.

An instructive case suggesting cyclical primary hyperparathyroidism

We report an instructive case of primary hyperparathyroidism in which cyclical secretion of PTH may have caused repeated hypercalcemic crises followed by temporary remission with a spontaneous drop in PTH. A 64-year-old man was admitted to our hospital twice with severe hypercalcemic crisis (corrected calcium (cCa) 15.0 mg/dl and 16.7 mg/dl) accompanied by an increase in intact PTH (220 pg/ml and 470 pg/ml). During both events, the serum PTH values spontaneously dropped followed by remission of the hypercalcemia. The tumor, detected at the left-upper side, showed neither vascularity on ultrasound examination nor washout delay on MIBI scintigraphy, suggesting that two parathyroid adenoma infarctions had occurred. Cervical exploration was undertaken. The histopathological examinations confirmed that the tumor was parathyroid adenoma. Contrary to our expectation, however, it did not reveal necrotic tissue that would indicate recent infarction. The findings in this case may be explained by cyclical secretion of PTH from a parathyroid adenoma. Although cyclical Cushing's syndrome is well known, to our knowledge this is the first documented case suggesting cyclical primary hyperparathyroidism.

Effect of fluoride and gonadal steroid deficiency on enamel and dentin mineralization of female rats

The aim of this study was to verify the influence of estrogen deficiency on enamel and dentin microhardness of female rats' incisors, as well as the influence of chronic administration of fluoride on that response. Sham or OVX rats drank distilled water or distilled water with 10 ppm fluoride as NaF, for 90 days. The upper incisors were removed and the specimens submitted to microhardness analysis of enamel and dentin. The data were compared by variance analysis and Tukey's test (p<0.05). There was a significant reduction in the mineralization of crown (7.9% and 8.1%) and root (20.4% and 25.0%) in both groups treated with fluoride or distilled water, respectively and an increase (14.2%) in the mineralization of coronal dentin after ovariectomy. Fluoride treatment did not cause reduction in enamel mineralization; however, it reduced dentin mineralization following ovariectomy. It was possible to conclude that estrogens directly or indirectly influence the process of enamel and dentin mineralization of female rats' incisors. The results also indicate that enamel and dentin exhibit different responses to fluoride administration.

Normocalcemia with elevated parathyroid hormone levels after surgical treatment of primary hyperparathyroidism

BACKGROUND

Thirty percent of patients who undergo successful parathyroidectomy for primary hyperparathyroidism show unexplained elevated postoperative serum parathyroid hormone (PTH) levels despite normocalcemia.

METHODS

PTH levels were measured monthly in 97 patients for 6 months after parathyroidectomy. Renal function, 25-OH-vitamin D levels, serum alkaline phosphatase levels, osteocalcin, and bone densitometry were evaluated before and 6 months after surgery. PTH reactivity to calcium loading was tested at the sixth month.

RESULTS

Thirty patients had elevated PTH levels despite normocalcemia after parathyroidectomy. Before surgery, these 30 patients had higher PTH and creatinine levels, lower vitamin D levels, and more extensive bone involvement than those with normal postoperative PTH levels. In patients with normal renal function and normal vitamin D levels, postoperative PTH values correlated with preoperative PTH levels but not with bone disease.

CONCLUSION

In most cases, elevated PTH levels after surgery is an adaptive reaction to renal dysfunction or vitamin D deficiency. If no adaptive cause can be found, persistent hyperparathyroidism must be suspected.

Calcium and the risk for periodontal disease

BACKGROUND

Dietary calcium has long been a candidate to modulate periodontal disease. Animal as well as human studies of calcium intake, bone mineral density, and tooth loss provide a rationale for hypothesizing that low dietary intake of calcium is a risk factor for periodontal disease.

METHODS

We evaluated the role of dietary calcium intake as a contributing risk factor for periodontal disease utilizing the Third National Health and Nutrition Examination Survey (NHANES III), which is representative of the U.S. civilian non-institutionalized population. Dietary calcium intake was determined from a 24-hour dietary recall. The U.S. Department of Agriculture Nutrient Database was used as a source of nutrient composition data. Periodontal disease was measured by attachment loss. In addition, serum calcium was assessed using venous blood samples. Logistic regression analysis was used to examine the association between periodontal disease and dietary calcium intake or serum calcium levels after adjusting for covariants including age, gender, tobacco consumption, and gingival bleeding.

RESULTS

The association of lower dietary calcium intake with periodontal disease was found for young males and females (20 to 39 years of age), and for older males (40 to 59 years of age). The relationship between low dietary calcium intake and increased levels of periodontal disease showed an estimated odds ratio (OR) of 1.84 (95% CI: 1.36 to 2.48) for young males, 1.99 (95% CI: 1.34 to 2.97) for young females, and 1.90 (95% CI: 1.41 to 2.55) for the older group of males. These odds ratios were adjusted for gingival bleeding and tobacco consumption. The dose response was also seen in females, where there was 54% greater risk of periodontal disease for the lowest level of dietary calcium intake (2 to 499 mg) and 27% greater risk in females who took moderate levels of dietary calcium (500 to 799 mg) as compared to those who took 800 mg or more dietary calcium per day. A statistically significant association between low total serum calcium and periodontal disease was found in younger females aged 20 to 39 with OR = 6.11 (95% CI: 2.36 to 15.84) but not for males or older females, after adjusting for tobacco use, gingival bleeding, and dietary calcium intake.

CONCLUSIONS

These results suggest that low dietary intake of calcium results in more severe periodontal disease. Further studies will be needed to better define the role of calcium in periodontal disease and to determine the extent to which calcium supplementation will modulate periodontal disease and tooth loss.

The effect of hormone replacement therapy on salivary calcium concentrations in menopausal women

Hormone replacement therapy in menopausal women is known to affect the general calcium turnover of the body. No information is available about the effects of hormone therapy on salivary electrolytes and on calcium in particular. A group of 16 healthy peri- and postmenopausal women, all recommended to start hormone replacement therapy, were studied longitudinally for 5 months. Paraffin-stimulated whole saliva was collected at baseline, at 3 and at 5 months after the onset of therapy, and analysed for calcium, sodium and potassium concentrations. In response to hormone replacement therapy, calcium concentration decreased (p = 0.037), that of sodium increased (p = 0.019), while no change was observed in the potassium concentrations during the follow-up period.

Calcium-sensing receptor expression and signalling in human parathyroid adenomas and primary hyperplasia

OBJECTIVE

Both in vivo and in vitro evidence indicates that primary hyperparathyroidism is characterized by a reduced sensitivity to extracellular calcium ([Ca2+]o). The existence of alterations in the expression and signalling of calcium sensing receptor (CaSR) in parathyroid neoplasia is still uncertain. In order to clarify the role of CaSR in the reduced [Ca2+]o sensing of parathyroid neoplasia we investigated PTH secretion and intracellular effectors triggered by CaSR activation as well as the levels of expression of CaSR and CaSR coupled G proteins (Gq/G11) in parathyroid adenomas and primary hyperplasia.

MATERIALS AND METHODS

The study included 27 parathyroid adenomas, 4 cases of primary hyperplasia and pools of normal parathyroid biopsies. Tissues were either snap frozen in liquid nitrogen or placed in sterile medium for cell dispersion. The effects of increasing [Ca2+]o on in vitro PTH release, intracellular cAMP levels and intracellular calcium ([Ca2+]i) in cells loaded with the Ca2 + indicator fura-2 were evaluated. CaSR mRNA levels were assessed by semiquantitative RT-PCR analysis, using GAPDH as internal standard, while CaSR protein was detected by western blot analysis using a specific polyclonal antibody. Purified antisera selective for G11alpha and Gqalpha were used to detect this class of proteins.

RESULTS

In basal conditions (at 0.5 mM [Ca2+]o) in vitro PTH released ranged from 29.4 to 1186 pg/well/60 minutes. Increasing [Ca2+]o from 0.5 to 1, 2.5 and 5 mM caused a variable effect. One group (n = 7) showed a significant but partial reduction of PTH release (of 17 to 60% of basal levels) that occurred at physiological [Ca2+]o concentrations (1 mM) while the remainder showed either inhibition detectable only at 2.5 mM (n = 15) or total (n = 9) resistance to [Ca2+]o. In the responsive cells, [Ca2+]o (1-5 mM) caused a pertussis toxin-insensitive [Ca2+]i rise (ranging from 10% to 260%), due to Ca2+ release from intracellular stores, and an inhibition of forskolin-stimulated cAMP levels. By RT-PCR almost all tumours tested showed a substantial reduction in CaSR mRNA levels when compared to the normal tissue (CaSR/GAPDH ratio: 3.1 +/- 0.5 vs. 15.5 +/- 3.1; P < 0.001), which was confirmed by immunoblotting analysis demonstrating low levels of CaSR protein in tumour tissues. Moreover, low amounts of G11alpha and Gqalpha, the G proteins involved in CaSR coupling, were observed in the majority of pathological tissues.

CONCLUSIONS

The study shows that the activation of the calcium sensing receptors expressed in adenomatous parathyroid glands modulates intracellular effectors in a similar way to those operating in the normal parathyroid. Although a reduction of calcium sensing receptor expression is probably involved in the poor inhibition of PTH release induced by [Ca2+]o, this is not the only factor altering [Ca2+]o sensing in parathyroid adenomas, since tumours characterized by different in vitro sensitivity to [Ca2+]o showed similar CaSR levels. The low content of G proteins of the Gq subfamily might represent an additional alteration leading to a defective [Ca2+]o sensing.

Effect of an oral calcium load on urinary markers of collagen breakdown

Aim of this study was to investigate whether osteoclast activity changes as a consequence of even mild physiological perturbation of plasma calcium as such induced by an oral calcium load. Osteoclast activity was determined indirectly by measuring, in spot urines at two and four hours after oral calcium load, the urinary excretion of hydroxylysylpyridinoline (Pyr), deoxylysylpyridinoline (D-Pyr), hydroxyproline (Hyp) and galactosyl-hydroxylysine (GHyl). The occurrence of the metabolic perturbation of plasma calcium homeostasis was assessed by measuring three indexes: i.e. calcemic response, PTH reduction and calciuric response at times following oral calcium loading. A significant fall of urinary D-Pyr and Pyr followed the perturbation of calcium homeostasis induced by the oral calcium load in two groups of healthy young adult and postmenopausal women. The highest mean percent reduction was observed for D-Pyr and was quantitatively similar in the two groups. Since urinary D-Pyr is the most specific bone resorption marker, it may be inferred that the perturbation of plasma calcium homeostasis induced by an oral calcium load is able to acutely inhibit osteoclast activity. This supports the view that osteoclasts are involved in the short-term error correction of plasma calcium.

Calcium supplementation and prevention of pregnancy induced hypertension

In a randomized controlled trial 201 healthy nulliparous women were randomly allocated by means of a computer generated randomization list. From 20 weeks of gestation until delivery they received either 2 g of oral elemental calcium (n = 103) per day or an identical placebo (n = 98). Eleven women (5.47%) were lost to follow-up after randomization. The study groups were very similar at the time of randomization; with respect to several clinical and demographic variables. Treatment compliance was very similar in both groups as was determined by pill count. The rate of pregnancy induced hypertension was lower in the calcium group than in the placebo group 8.24%; vs 29.03%; (RR = 0.28; 95% CI 0.14-0.59). The incidence of gestational hypertension was 6.18% in the calcium group and 17.20% in the placebo group (RR = 0.28; 95% CI 0.08-0.80), and the incidence of preeclampsia was 2.06% in the calcium group and 11.82% in the placebo group (RR = 0.13; 95% CI 0.01-0.64). In conclusion calcium supplementation given in pregnancy to nulliparous women reduces the incidence of pregnancy induced hypertension.

Differences in PTH (1-84) release in response to ambient calcium concentrations of parathyroid adenoma fragments and dispersed parathyroid adenoma cells in culture

In a previous study we observed that during perfusion of normal human parathyroid tissue, the release of PTH (1-84) was modulated by ambient extracellular calcium (Ca++) and lithium (Li+) concentrations in the media and preliminary studies indicated that this stimulus-response coupling was absent in human parathyroid adenoma fragments. The present study compares the responsiveness of parathyroid adenoma fragments and isolated parathyroid adenoma cells from the same adenoma and their response to Ca++ changes and Li+ presence in culture media. The data indicate that parathyroid adenoma tissue fragments fail to respond to ambient changes in Ca++ and Li+. In contrast, dispersed parathyroid cells preparations responded with a significant increase of PTH (1-84) release (50%) under the influence of low ambient calcium concentrations. Six of the dispersed cell preparations also responded with a 45% decrease in PTH release under the influence of a high Ca concentration in the medium. Isolated parathyroid cells obtained from the same adenoma's did not respond to the presence of Li++ in the medium. These data suggest tat human parathyroid adenoma tissue functions autonomously and is not sensitive to calcium regulation in the tissue configuration as opposed to the isolated cell suspensions. The nature of this difference remains elusive.

Nocturnal rise in markers of bone resorption is not abolished by bedtime calcium or calcitonin

As assessed by urine pyridinium cross-links, bone resorption increases at night. This has been ascribed to either the nocturnal rise of serum parathyroid hormone (PTH) or immobilization. ICTP is the carboxyterminal telopeptide region of type I collagen in bone, cross-linked via pyridinium cross-links and liberated during the degradation of type I collagen. To study whether the nocturnal rise in bone resorption is seen also in serum type I collagen carboxyterminal telopeptide (ICTP) and whether this rise is abolished by bedtime calcium or calcitonin, nine healthy postmenopausal women participated in three 24 hour sessions. At 2200 hours, either 1 g of oral calcium or 200 IU of intranasal calcitonin or no treatment (control session) were given. The participants were recumbent from 2200 hours to 0600 hours. Like urinary pyridinolines, serum ICTP showed a clearcut nocturnal rise during the control session, increasing from 3.7 +/- 0.3 micrograms/liter (mean +/- SE) at 2000 hours to 4.9 +/- 0.4 micrograms/liter at 0600 hours (P < 0.001). Administration of calcium did not affect either serum ICTP or urinary pyridinolines, although it decreased serum intact PTH by 18% (P < 0.001) as assessed by areas under curve (AUC) after 2200 hours. Serum ICTP and urinary pyridinolines remained unchanged also after administration of calcitonin which increased the AUC for serum intact PTH by 9% (P < 0.05). In conclusion, serum ICTP follows a circadian rhythm in healthy postmenopausal women. The nocturnal rise in markers of bone resorption is not due to PTH, and its dependency on the function of osteoclasts is open to question.

Primary hyperparathyroidism

Primary hyperparathyroidism is not rare. It is particularly common after the age of 50 and may affect up to 3% of postmenopausal women. It is commonly found as a result of blood tests performed for other reasons and is therefore often asymptomatic. Surgical treatment is recommended for patients with renal stone disease, plasma calcium above 3 mmol/L and accelerated bone loss (e.g., bone density < 3 standard deviations below the young normal mean). There is considerable debate about whether mild asymptomatic disease should be treated, but if there is rapid bone loss, either surgical or medical therapy with hormones or bisphosphonates is indicated.

Progressive escape from parathyroid suppression: a common phenomenon in primary hyperparathyroidism (a calcium clamp study)

OBJECTIVE

Induced aggravation of hypercalcaemia in vivo and in vitro causes partial suppression of parathyroid hormone (PTH) secretion in primary hyperparathyroidism (PHP). Furthermore, one in-vitro study also demonstrates progressive escape from such action. The aim of the present in-vivo study was to examine whether escape from suppression is a common feature of PHP.

DESIGN

A rapid increment in blood ionized calcium (B-Ca2+) to 0.25-0.30 mmol/l above individual baselines was achieved by intravenous calcium infusions. This induced or aggravated hypercalcaemia was kept constant for 2 hours (controls) or 4 hours (patients).

PATIENTS AND CONTROLS

The study of PHP comprised 19 patients (18 females and one male) aged 39-85 years (geometric mean 66). For comparison we included the results obtained in a control group of 24 healthy subjects (11 women and 13 men) aged 20-68 years (geometric mean 32).

MEASUREMENTS

The individual levels of B-Ca2+ were controlled by frequent bedside measurements of B-Ca2+. The changes in serum intact parathyroid hormone (S-PTH(1-84)) were registered.

RESULTS

After 30 minutes of calcium infusion average concentrations of S-PTH(1-84) had decreased from 7.9 (6.7-9.4) pmol/l in PHP and 2.5 (2.1-2.9) pmol/l in controls to their respective nadir values of 2.9 (2.1-4.1) pmol/l and 0.6 (0.5-0.8) pmol/l. While S-PTH(1-84) remained suppressed at a stable level for 120 minutes in controls, in PHP it started to escape progressively after 30 minutes to a level of 4.2 (3.0-5.8) pmol/l (P < 0.001). Linear regression analysis of the individual S-PTH(1-84) observations in PHP, from 30 to 240 minutes of study, revealed that five patients did not escape (group A) while the remainder 14 patients escaped progressively (group B). Within group B, seven patients escaped significantly after 120 minutes, 10 after 180 minutes and 14 after 240 minutes. Although comparable respecting B-Ca2+ before and during calcium infusion, group A and B presented different S-PTH(1-84) curves. Thus, at times zero, 30, 120 and 240 minutes their respective average concentrations of S-PTH(1-84) measured 9.9 (9.1-10.9) vs 7.3 (5.9-9.0) (P < 0.02), 4.6 (3.7-5.7) vs 2.5 (1.6-3.9) (P < 0.01), 5.0 (3.9-6.5) vs 3.0 (1.9-4.8) (P < 0.05) and 5.2 (3.6-7.4) vs 3.9 (2.6-6.0) (NS) pmol/l.

CONCLUSIONS

We hypothesize that two different mechanisms are involved in the parathyroid response to the calcium clamp, an initial and fast inhibition of PTH release, while the subsequent course depends on the balance between the intra-glandular secretion rate of PTH and the intra-glandular capacity for PTH degradation. The escape from parathyroid suppression during a sustained stable increment in B-Ca2+ suggests that the basal secretion over-rides degradation in a majority of the patients with PHP.

Comparison of the suppressive effect of two doses (500 mg vs 1500 mg) of oral calcium on parathyroid hormone secretion and on urinary cyclic AMP

The respective effects of the ingestion of two different doses of calcium (500 and 1500 mg) on serum ionized calcium, intact parathyroid hormone (PTH 1-84), and the urinary excretion of 3',5'-cyclic adenosine monophosphate (cyclic AMP) were evaluated in 15 young male adults. Ionized serum calcium and PTH 1-84 were measured before and 1 hour, 2 hours and 3 hours (P1, P2, and P3) after the oral intake of calcium. Cyclic AMP was measured in 2-hour urine samples collected before and during 4 hours after the ingestion of calcium. Similar increments in serum ionized calcium (delta Ca2+) were observed except at P3 where the delta Ca2+ was significantly (P < 0.02) higher after 1500 mg (0.088 mmol/liter) than after 500 mg of (0.062 mmol/liter). In the same way, the comparison of the PTH 1-84 concentrations showed no statistical difference except at P3 (P < 0.002). When expressed as a percentage of P0, the P1 and P2 PTH 1-84 values were more suppressed after 1500 mg than after 500 mg of calcium (P1: -69% vs -59%; P < 0.02; P2: -66% vs -50%; P < 0.02). However, the simultaneous cyclic AMP responses (-24% vs -19%) were not significantly different. The results show that the respective maximal effects on PTH secretion and on urinary cyclic AMP of two very different oral doses of calcium are only slightly different.

Suppressibility of serum levels of PTH by calcium in the immediate postoperative period after surgery for primary hyperparathyroidism

The ability of calcium to suppress the secretion of parathyroid hormone (PTH) is impaired in primary hyperparathyroidism (pHPT). Whether the nonadenomatous glands in pHPT also exhibit altered calcium/PTH homeostasis is not known, but this may be the case since in the immediate postoperative period after surgery for pHPT, hypocalcemia often evolves in spite of a rapid normalization of serum levels of PTH. In this study, therefore, the suppression of serum levels of PTH by an oral calcium load was investigated pre- and postoperatively in 12 patients operated on for parathyroid adenoma. There was no difference in the calcemic response during the calcium load pre- and postoperatively. We found that the suppression of serum levels of PTH by calcium was increased already on the first postoperative day. However, postoperatively, the suppression of serum levels of PTH correlated positively to serum levels of ionized calcium and, furthermore, negatively to the weight of the excised parathyroid adenoma and the preoperative serum levels of ionized calcium. The results indicate that the function of the remaining parathyroid glands in patients with parathyroid adenoma could have been altered during the hyperparathyroid state and that postoperative hypocalcemia more readily evolves in patients with severe pHPT and impaired suppressibility of PTH (by calcium) in the remaining parathyroid glands.

Parathyroid gland function in chronic renal failure

The concept that the PTH-calcium curve is representative of parathyroid function has been discussed. Comparisons of parathyroid function have been made between normal humans and hemodialysis patients and also between hemodialysis patients with different forms of renal osteodystrophy. From these comparisons, it is apparent that the magnitude of HPT is much greater in patients with renal failure than in normal humans, and as represented by the ratio of basal to maximal PTH, the parathyroid gland appears to be stimulated at basal serum calcium levels in hemodialysis patients. Similarly, based on an analysis of the PTH-calcium curve, we were able to determine that several differences in parathyroid function were present in hemodialysis patients with different forms of renal osteodystrophy. As compared to hemodialysis patients with LTAABD and aplastic bone disease, patients with osteitis fibrosa have a greater magnitude of hyperparathyroidism, a greater sensitivity of the parathyroid cell (slope), a higher set point of calcium, and greater PTH stimulation at basal serum calcium (ratio of basal to maximal PTH). Calcitriol treatment of hemodialysis patients with osteitis fibrosa resulted in a significant decrease in PTH throughout the PTH-calcium curve and also reduced the sensitivity (slope) of the PTH-calcium curve. The concept of hysteresis has been discussed as well as the role that the ambient basal serum calcium concentration may have on the determination of the PTH-calcium curve. Finally, the effect that successful renal transplantation has on HPT has been examined. In conclusion, we believe that the PTH-calcium curve provides a reliable assessment of parathyroid function, and as such, has considerable application for the study of parathyroid disorders in the clinical setting.

Calcium regulating hormones after oral and intravenous calcium administration

The aim of this study was to determine the changes in serum calcium concentration and in the concentrations of calcium regulating hormones after a single oral or intravenous calcium administration. Standard dosages of calcium, as used in routine patient care, were employed. Intact parathyrin, calcitonin, calcitriol, calcidiol, total calcium, ionized calcium, total protein and phosphate were determined in 12 healthy young men before and up to 8 h after oral and intravenous administration of calcium. During a fortnight there were four study days with 1000 mg calcium orally (p.o.), 2000 mg orally, 180 mg calcium intravenous (i.v.) and a control day without calcium. During the study the men were on a low calcium diet. We observed a sharp increase in the calcium concentration after i.v. administration (15 min: total Ca: + 0.48 +/- 0.32 mmol/l; ionized Ca: + 0.25 +/- 0.15 mmol/l; p < 0.01). The concentration increase after the two oral loads was nearly identical. The maximal concentration of total calcium was reached after 120 min (1000 mg: + 0.1 +/- 0.04 mmol/l; p < 0.001; 2000 mg: + 0.12 +/- 0.04 mmol/l; p < 0.001). There was a significant increase in urinary calcium after all modes of calcium administration. Calcitonin increased significantly only after i.v. injection of calcium (+ 9.2 +/- 3.4 pmol/l; p < 0.001) while parathyrin decreased significantly after all modes of calcium administration (i.v.: 15 min: -1.9 +/- 0.88 pmol/l; p < 0.01; 1000 mg: 90 min: -0.78 +/- 0.75 pmol/l; p < 0.001; 2000 mg: 90 min: -1.02 +/- 0.57 pmol/l; p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Dynamics of parathyroid hormone release and serum calcium regulation after surgery for primary hyperparathyroidism

Analysis of 14 patients with primary hyperparathyroidism (HPT) prior to and during the first year after parathyroid surgery disclosed that the operation was associated with rapid reductions of intact serum parathyroid hormone (PTH) and total serum and ionized plasma calcium values. A decreased urinary calcium excretion, a gradual elevation of renal calcium reabsorption, a transient reduction of serum calcitriol, and a late increase in 25-hydroxycholecalciferol values were also noted. Dynamic tests of parathyroid function by EDTA infusion and an oral calcium load revealed a sigmoidal relationship between serum PTH and calcium levels, and that parathyroid surgery induced considerable changes in both the position and slope of the dose-response curve. It was also apparent that PTH release was submaximally stimulated event at periods of hypocalcemia. The findings substantiate that adjustments of PTH release to acute alterations of serum calcium occur along the prevailing dose-response relationship, while stimuli being maintained for longer periods of time induce compensatory shifts in the position and slope of this curve. It is further suggested that unknown factors with PTH-like function may participate in the calcium regulation after surgery for primary HPT.

Calcium supplementation to prevent hypertensive disorders of pregnancy

BACKGROUND

Calcium supplementation has been reported to reduce blood pressure in pregnant and nonpregnant women. We undertook this prospective study to determine the effect of calcium supplementation on the incidence of hypertensive disorders of pregnancy (gestational hypertension and preeclampsia) and to determine the value of urinary calcium levels as a predictor of the response.

METHODS

We studied 1194 nulliparous women who were in the 20th week of gestation at the beginning of the study. The women were randomly assigned to receive 2 g per day of elemental calcium in the form of calcium carbonate (593 women) or placebo (601 women). Urinary excretion of calcium and creatinine was measured before calcium supplementation was begun. The women were followed to the end of their pregnancies, and the incidence of hypertensive disorders of pregnancy was determined.

RESULTS

The rates of hypertensive disorders of pregnancy were lower in the calcium group than in the placebo group (9.8 percent vs. 14.8 percent; odds ratio, 0.63; 95 percent confidence interval, 0.44 to 0.90). The risk of these disorders was lower at all times during gestation, particularly after the 28th week of gestation (P = 0.01 by life-table analysis), in the calcium group than in the placebo group, and the risk of both gestational hypertension and preeclampsia was also lower in the calcium group. Among the women who had low ratios of urinary calcium to urinary creatinine (less than or equal to 0.62 mmol per millimole) during the 20th week of gestation, those in the calcium group had a lower risk of hypertensive disorders of pregnancy (odds ratio, 0.56; 95 percent confidence interval, 0.29 to 1.09) and less of an increase in diastolic and systolic blood pressure than the placebo group. The pattern of response was similar among the women who had a high ratio of urinary calcium to urinary creatinine during the 20th week of gestation, but the differences were smaller.

CONCLUSIONS

Pregnant women who receive calcium supplementation after the 20th week of pregnancy have a reduced risk of hypertensive disorders of pregnancy.

Cellular physiology and pathophysiology of the parathyroid glands

This report provides insight into parathyroid gland physiology and the pathophysiology of hyperparathyroidism (HPT). Increases in the extracellular calcium concentration constitute the primary physiological signal for inhibition of parathyroid hormone (PTH) release. Transduction of the external signal into a cellular response involves activation of a cation receptor mechanism on the plasma membrane with rapid rise in the cytoplasmic calcium concentration of the cells. This recently discovered parathyroid calcium receptor has been characterized as a glycoprotein of unusually high molecular weight, which may play a key role in calcium homeostasis since it is also expressed in the kidney and placenta. Binding of external calcium to the receptor is associated with mobilization of intracellular calcium as well as calcium influx into the cells and phosphoinositol hydrolysis. These events rapidly interfere with the release process through essentially unknown mechanisms and probably also at sustained stimulation inhibit PTH gene transcription. The relative calcium insensitivity of the PTH release in HPT is associated with a deranged regulation of cytoplasmic calcium within pathological parathyroid cells. The molecular basis for this disturbance comprises down regulation of the cation receptor, whereby external calcium is translated into abnormally low levels of cytoplasmic calcium and insufficient inhibition of PTH release. Studies on expression of the functionally important cation sensing glycoprotein and its associated cellular signal systems may provide novel means for interference with the pathophysiological derangements of HPT.

Differential diagnosis of hypercalcemia

The differential diagnosis of hypercalcemia has expanded to over 25 separate disease states, with primary hyperparathyroidism and malignancy accounting for 80-90% of all hypercalcemic patients. Primary hyperparathyroidism comprises the majority of hypercalcemic patients among the ambulatory population, but malignancy accounts for up to 65% of such patients in the hospital. Factors favoring primary hyperparathyroidism include a family history of hyperparathyroidism or multiple endocrine neoplasia, a history of childhood radiation to the head and neck, the postmenopausal state, a history of renal calculi or peptic ulcer, hypertension, the induction of hypercalcemia by thiazides, or an asymptomatic patient with a prolonged, stable mild hypercalcemia. The usefulness of the serum calcium, parathyroid hormone, chloride, phosphorus, serum 25-OHD, and 1,25-(OH)2D, and urinary calcium in the differential diagnosis of hypercalcemia is discussed. The pitfalls of an excessive reliance on the serum PTH in diagnosing hyperparathyroidism are stressed. The discriminant values of the serum calcium, chloride, phosphorus, and parathyroid hormone are explored, with the serum parathyroid hormone, chloride, and calcium proving most useful in separating primary hyperparathyroidism from other forms of hypercalcemia. Multivariate discriminant analysis using the serum calcium, phosphorus, and chloride and the hematocrit achieves an accuracy of 95-98% and is the most economical method of identifying hyperparathyroidism. The addition of the amino-terminal or intact PTH assay increases the accuracy to 99% and is essential in the presence of renal insufficiency.

The effect of a standard oral calcium load given in two different forms on plasma ionized calcium and serum PTH

A standard dose (1 g, 25.4 mmol) of calcium was administered both as calcium chloride in syrup and as Calcium-Sandoz Syrup (calcium glubionate and calcium galactogluconate) to 10 volunteers. Both dosage forms caused a significant rise in ionized calcium and a significant fall in concentration of serum PTH, the calcium chloride producing significantly greater changes. The urinary excretion of calcium measured over 5 h after calcium chloride was double that after Calcium-Sandoz. Calcium chloride, as expected, also gave rise to a decreased urine pH. Calcium chloride would be the better choice for an oral PTH suppression test.