Potassium metabolism in continuous ambulatory peritoneal dialysis patients

Background: Hypokalemia is common and may have contributed to the poor clinical outcome in peritoneal dialysis (PD) patients. In this study, we made a detailed investigation on the potassium metabolism in continuous ambulatory peritoneal dialysis (CAPD) patients and tried to find out the possible factors associated with the high prevalence of hypokalemia in PD patients. Methods: A cross-sectional survey in 243 clinically stable CAPD patients was made in our PD center in 2010. Patients were divided into four groups according to whether they were anuric or not and different dialysis regimens. Patients’ demographic data and data on potassium metabolism including dietary potassium intakes, residual renal potassium, and peritoneal dialysis potassium removal were collected. Results: The average potassium intake in our 243 PD patients was 32.1?±?11.1?mmol/day. The total potassium removal was significantly higher in non-anuric patients as compared to anuric patients (33.2?±?9.1 vs. 23.0?±?4.7?mmol/day for 3 exchanges per day and 35.2?±?8.9 vs. 28.6?±?6.3?mmol/day for 4 exchanges per day, respectively, p?p?p?p?R² linear?=?0.645, p?Conclusions: Our study suggested that if potassium intake was limited in PD patients, we should be aware of the risk of hypokalemia with high doses of PD when patients have good RRF. Our study also suggested that potassium removal in PD patients may not necessarily reflect potassium intake even if serum potassium is normal, the effect of ICW should be considered when evaluating potassium homeostasis.     

Serum Magnesium Measurements After Parathyroidectomy for Primary Hyperparathyroidism: Should It be Routine?

Background

Parathyroidectomy is the treatment of choice in primary hyperparathyroidism (PHPT). Following surgery, significant changes in bone and mineral metabolism may follow, but routine magnesium monitoring is not standard practice. The occurrence of significant clinical events linked to hypomagnesaemia in 3 patients after parathyroidectomy led to our evaluation of magnesium levels after surgery for PHPT.

Methods

Serum magnesium levels before and after parathyroidectomy for PHPT were prospectively evaluated in a single centre over a year. The incidence and severity of hypomagnesaemia and its correlation with other biochemical variables were assessed.

Results

A total of 138 patients underwent parathyroidectomy for PHPT. Pre-operative and day 1 post-operative serum magnesium levels were available in 57/138 (41.3%) and 99/138 (71.7%) patients, respectively. Serum magnesium decreased significantly after surgery (mean ± SD of 0.85 ± 0.08 and 0.75 ± 0.11 mmol/L, respectively, p < 0.001). On the day after parathyroidectomy, 31/99 (31.3%) patients had hypomagnesaemia (<0.70 mmol/L); in 3 of whom it was severe (<0.50 mmol/L). Patients with hypomagnesaemia had lower pre-operative magnesium (mean ± SD of 0.78 ± 0.06 and 0.87 ± 0.07 mmol/L, p < 0.001), higher pre-operative calcium [median (IQR) of 2.83 (2.71–2.99) and 2.71 (2.63–2.80) mmol/L, p = 0.001] and higher post-operative calcium [median (IQR) of 2.41 (2.30–2.51) and 2.35 (2.28–2.43) mmol/L, p = 0.046] compared to those with normomagnesaemia. In addition, these patients demonstrated higher drop in calcium levels after surgery (0.44 ± 0.20 and 0.35 ± 0.18 mmol/L, p = 0.033). Magnesium levels after surgery correlated positively with pre-operative magnesium (r = 0.561, p < 0.001) and post-operative PTH (r = 0.210, p = 0.037) and negatively with pre-operative adjusted calcium (r = − 0.389, p < 0.001).

Conclusions

Serum magnesium decreased significantly following parathyroidectomy for PHPT and nearly a third of patients developed post-operative, mostly mild hypomagnesaemia. Whilst routine serum magnesium measurements could facilitate prompt recognition and treatment of this electrolyte disturbance, further research needs to establish the clinical importance of mild hypomagnesaemia in these clinical settings and, if indicated, to devise optimal treatment strategies.

     

Total and regional bone mineral content in Spanish professional ballet dancers

Total body bone mineral content (TBBMC) and regional bone mineral content (BMC) was measured in the members of the Spanish National Dance Company (15 female, mean age 25.1±3.8 years, and 15 male, mean age 28.2±2.1 years) and in 30 controls (15 women, mean age 26.1±1.8 years, and 15 mean, mean age 28.0±1.5 years). Ca, P, and Mg intake were greater in the group of ballet dancers than in controls analysis of variance (ANOVA, allP<0.0001). BMC was similar in the group of ballet dancers and controls except in the trunk without pelvis (P<0.001). Both male and female dancers weighed less than controls (P<0.05). The BMC of the male dancers was less than that of male controls only in the trunk (P<0.05) and in the trunk without pelvis (P<0.005); BMC was lower in female dancers than in female controls only in the arms and in the trunk without pelvis (P<0.05 andP<0.005, respectively). TBBMC, adjusted for weight and age, was correlated partially with caloric intake (kcal/day) and with Ca, P, Mg, and Zn intake (g/day), and yielded significant differences between the dancers and controls only in P intake (P<0.01), and between male dancers and male controls only in caloric intake and in Ca, P, and Zn intake (allP<0.01, except for Ca,P<0.05). The lower trunk bone mass observed in the female dancers is a risk factor for eventual osteoporosis.     

Acute Responses of Parathyroid Hormone and 1,25 Dihydroxyvitamin D3 to Unilateral Nephrectomy in Healthy Donors

Plasma immunoreactive parathyroid hormone (iPTH), 1,25(OH)₂D3calcium and phosphate and urinary creatinine, calcium and phosphatewere measured before and following unilateral nephrectomy insix kidney donors. Unexpectedly, plasma calcium rose, from 2.27±0.02mmol/l (mean±SEM) to 2.41±0.03 mmol/l on day 7and to 2.37±0.02 mmol/l on day 30 (P<0.02). A parallelrise in iPTH occurred, from 0.61±0.16 ng/ml initially,to 1.83±0.54 ng/ml on day 7 (P<0.05) and to 1.18±0.18on day 30 (P<0.01). The ratio of maximal tubular reabsorptionof phosphate to GFR (TmP/GFR) fell by day 2 (P<0.001), remainingreduced on day 30 (P<0.05). The significance of elevated iPTH in renal insufficiency wasfurther assessed by determining the time course of the disappearanceof iPTH after parathyroidectomy in three haemodialysis subjects.Fifty per cent baseline iPTH level occurred after an averageof 104.7 min, suggesting that the assay did not predominantlyrecognize C-terminal PTH fragments. By day 2, plasma 1,25(OH)₂D3had fallen from 34.3±4.5 pg/ml to 22.8±3.8 pg/ml(P<0.001), but by day 4 had regained its pre-nephrectomyvalue. Our results suggest that hypocalcaemia may not be thesole stimulus to parathyroid hormone secretion. It is speculatedthat reduction in circulating 1,25(OH)₂D3 may be involved.     

Bariatric Surgery Cannot Prevent Tryptophan Depletion Due to Chronic Immune Activation in Morbidly Obese Patients

Background: Increased activity of the immuno-modulatory enzyme indoleamine-2,3-dioxygenase (IDO) during immune activation, results in tryptophan depletion. Tryptophan metabolic changes reduce serotonin production and cause mood disturbances, depression, and impaired satiety, ultimately leading to increased food intake and obesity. Bariatric surgery significantly diminishes immune mediators by substantial weight reduction. We examined IDO-mediated tryptophan-catabolism in morbidly obese patients compared to lean individuals. Methods: Serum concentrations of kynurenine and tryptophan, calculated kynurenine to tryptophan ratios (kyn trp-1) as an indirect estimate of IDO activity, and neopterin levels reflecting IFN-γ mediated immune activation, were assessed before and after bariatric surgery. The study population included 22 morbidly obese individuals and 20 normal-weight volunteers. Results: Median weight loss after 24.4±5.1 months was 40.6 kg resulting in a reduction of BMI from 44.1 kg/m² to 29.9 kg/m² (P<0.001). Preoperative kyn trp-1 in morbidly obese patients was significantly increased compared to the control group (41.6±20.1 mmol/mol vs 26.5±5.1 mmol/mol; P<0.001). Postoperative weight reduction did not lead to normalization of kyn trp-1 (37.9±14.0 mmol/mol). As a consequence, tryptophan levels were significantly lower in morbidly obese patients (pre-: 51.5±9.2 μmol L⁻¹ and postoperatively: 46.9±7.6 μmol L⁻¹) when compared with those of normal-weight controls (64.8±9.5 μmol L⁻¹; P<0.001). In addition, neopterin levels were elevated in the study population pre- and postoperatively compared to normal-weight volunteers (both P<0.001). Conclusions: Tryptophan depletion in morbidly obese patients is due to chronic immune activation and persists in spite of significant weight reduction following bariatric surgery. This might thereby be responsible for diminished serotonin functions, leading to unchanged satiety dysregulation and a reward-deficiency-syndrome.     

CELLULAR POTASSIUM DEPLETION PREDISPOSES TO HYPOKALAEMIA AFTER ORAL SODIUM PHOSPHATE

Background : Oral sodium phosphate has become an attractive alternative to polyethylene glycol for colonic cleansing preparatory to elective colorectal surgery. Its use, however, has been associated with hypokalaemia. The authors of the present study tested the hypothesis that patients with cellular depletion of potassium are at significant risk for hypokalaemia with oral sodium phosphate bowel preparation. Methods : In 23 patients, total body potassium was measured by whole-body counting and intracellular water volume was measured by bioimpedance analysis before oral sodium phosphate bowel preparation. Patients were divided into those whose serum potassium fell to 3.5 mmol/L or lower (Group 1) and those whose did not after sodium phosphate treatment (Group 2). Results : The fall in serum potassium concentration over the period of oral sodium phosphate administration was significantly negatively correlated with intracellular potassium concentration measured prior to administration (r=-0.65, P= 0.0009). In Group 1, serum potassium concentration fell from 4.1 ± 0.1 (standard error of the mean (SEM)) mmol/L to 3.2 ± 0.1 mmol/L (P± 0.0001) while in Group 2 there was no significant change in this concentration (4.0 ± 0.1 vs 3.9 ± 0.1 mmol/L) as a result of sodium phosphate treatment. Intracellular potassium concentration prior to administration of sodium phosphate was significantly lower in Group 1 (117 ± 9 mmol/L vs 143 ± 7 mmol/L, P < 0.05). Conclusions : Caution should be exercised when treating patients with oral sodium phosphate who are considered to be cellularly depleted of potassium. These patients are at risk of hypokalaemia after this treatment.     

Identification of Risk Factors for Perioperative Mortality in Acute Mesenteric Ischemia

Introduction Acute intestinal ischemia is in most cases a lethal condition with a low survival rate. Risk factors of perioperative mortality are poorly defined. The aim of this study was to define risk factors that predict an adverse outcome of acute mesenteric ischemia (AMI). Methods A total of 132 consecutive patients (73 men, 59 women), mean ± SD age 71.96 ± 13.64 years, who underwent surgery because of AMI in a university tertiary care center were evaluated over a period of 10 years. Clinical features, laboratory findings, etiologic factors, and surgical procedures were recorded and assessed as possible risk factors for perioperative mortality. Results Of 132 patients, 86 (65.2%) died during the perioperative period as a direct result of AMI. Significant univariate predictors of perioperative mortality were age (P = 0.01), cardiopathy (P = 0.002), digoxin intake (P = 0.015), shock (P = 0.01), urea plasma level (P < 0.001), creatinine (P < 0.001), potassium (P = 0.042), low pH (P = 0.015) and bicarbonate (P = 0.035); hemoglobin ≥ 2.48 mmol/L (P = 0.035); time delay to surgery (P = 0.023); colonic involvement (P < 0.001); small and large bowel involvement (P < 0.001); arterial versus venous ischemia (P = 0.007); and intestinal resection (P < 0.001). In the multivariate analysis, the variables previous cardiac illness (P = 0.045), urea plasma levels (P < 0.001), and small and large bowel involvement were identified as independent risk factors of perioperative mortality. Intestinal resection (P < 0.001) was a favorable predictor. Conclusions Age, time delay to surgery, shock, and acidosis significantly increase the risk of mortality due to AMI, whereas intestinal resection has a protective effect. However, only previous cardiac illness, acute renal failure, and large bowel ischemia have a negative effect as independent risk factors of mortality of AMI.     

Potassium citrate supplementation results in sustained improvement in calcium balance in older men and women

The dietary acid load created by the typical Western diet may adversely impact the skeleton by disrupting calcium metabolism. Whether neutralizing dietary acid with alkaline potassium salts results in sustained improvements in calcium balance remains controversial. In this randomized, double‐blind, placebo‐controlled study, 52 men and women (mean age 65.2 ± 6.2 years) were randomly assigned to potassium citrate 60 mmol/d, 90 mmol/d, or placebo daily with measurements of bone turnover markers, net acid excretion, and calcium metabolism, including intestinal fractional calcium absorption and calcium balance, obtained at baseline and at 6 months. At 6 months, net acid excretion was significantly lower in both treatment groups compared to placebo and it was negative, meaning subjects' dietary acid was completely neutralized (?11.3 mmol/d on 60 mmol/d; ?29.5 mmol/d on 90 mmol/d, p < 0.001 compared to placebo). At 6 months, 24‐hour urine calcium was significantly reduced in persons taking potassium citrate 60 mmol/d (?46 ± 15.9 mg/d) and 90 mmol/d (?59 ± 31.6 mg/d) compared with placebo (p < 0.01). Fractional calcium absorption was not changed by potassium citrate supplementation. Net calcium balance was significantly improved in participants taking potassium citrate 90 mmol/d compared to placebo (142 ± 80 mg/d on 90 mmol/d versus ?80 ± 54 mg/d on placebo; p = 0.02). Calcium balance was also improved on potassium citrate 60 mmol/d, but this did not reach statistical significance (p = 0.18). Serum C‐telopeptide decreased significantly in both potassium citrate groups compared to placebo (?34.6 ± 39.1 ng/L on 90 mmol/d, p = 0.05; ?71.6 ± 40.7 ng/L on 60 mmol/d, p = 0.02) whereas bone‐specific alkaline phosphatase did not change. Intact parathyroid hormone was significantly decreased in the 90 mmol/d group (p = 0.01). Readily available, safe, and easily administered in an oral form, potassium citrate has the potential to improve skeletal health. Longer‐term trials with definitive outcomes such as bone density and fracture are needed. © 2013 American Society for Bone and Mineral Research.     

INSULIN AND MINERALOCORTICOIDS INFLUENCE ON EXTRARENAL POTASSIUM METABOLISM IN CHRONIC HEMODIALYSIS PATIENTS

Insulin-mineral corticoids effects on extrarenal K⁺ metabolism in dialysis patients. During the inter-dialytic interval in dialyzed patients, hydrogen and potassium ions are regulated by extrarenal mechanisms. We studied the hormonal and acidotic effects on the extrarenal potassium metabolism, in selected, anuric and stable, hemodialysis patients. Fifteen patients, were grouped according to the mean mid-week pre-dialysis K⁺ over the past 12 months: > 6.0 mEq/L (G1, n = 5), = 5.1–6.0 mEq/L (G2, n = 5), ≤5.0 mEq/L (G3, n = 5). After a mid-week hemodialysis session and 12 h fasting, they received 1 g/Kg glucose p.os (A). Insulin, aldosterone, renin, pH, HCO₃^?, glucose, body weight, blood pressure and heart rate were measured before and 60′ after the meal. We recorded the same parameters, except insulin, in 15 patients, similarly grouped, before hemodialysis (T0) and on 3 consecutive off dialysis days (T1–T3); G1 received fluorohydrocortisone (FHC) 0.1 mg–0.3 mg/day, according to body weight and G3 spironolactone (SLT) 200 mg per day. G2 were controls (B). (A) A significant rise in glycemia (81 ± 23 to 157 ± 52 mg/dL, P < 0.001) and insulin (11.8 ± 6.2 to 46.8 ± 19.5 μU/mL, P<0.001), with a drop in K⁺ (5.1 ± 0.6 to 4.8 ± 0.7 mEq/L, P= 0.001) and aldosterone (453 ± 373 to 383 ± 364 pg/mL, P<0.01), were noted at T60 vs. T0, in all groups. Insulin levels correlated negatively (r = ?0.54, P<0.04) to serum K⁺ at T60, in all patients. (B) No major pH, HCO₃ and aldosterone changes were observed in the 3 groups. Despite that, K⁺ dropped in G1 by FHC (6.7 ± 0.9 to 5.9 ± 0.6 mEq/L, P<0.05), rose in G3 by SLT (4.4 ± 0.4 to 5.4 ± 0.3 mEq/L, P<0.05) and remained unchanged in controls (5.8 ± 0.2 to 5.8 ± 0.6 mEq/L), (T0 vs T3 pre-dialysis values). Glucose significantly lowered K^? by promoting adequate insulin secretion. Drugs affecting aldosterone action significantly influenced potassium metabolism. Acid-base balance was not important in K⁺ handling in steady state anuric dialysis patients.     

Efficacy of wheat germ lectin-precipitated alkaline phosphatase in serum as an estimator of bone mineralization rate: Comparison to serum total alkaline phosphatase and serum bone Gla-protein

Summary Serum levels of total alkaline phosphatase activity (S-T-AP), wheat germ lectin-precipitated alkaline phosphatase activity (S-L-AP), and bone Gla-protein immunoreactivity (S-BGP) were measured in 26 patients (23 females and 3 males) aged 35–73 years (mean 59 years) with primary hyperparathyroidism (n=7), hyperthyroidism (n=9), and hypothyroidism (n=10) in whom the bone mineralization rate (m) was determined by⁴⁷Ca-kinetics (continuously expanding calcium pool model). A weak positive correlation (r=0.42,P<0.05) was found between S-T-AP and m, which in the range from 0–18 mmol Ca/day could be estimated with a standard error of 4.6 mmol/day. A closer correlation (r=0.65,P<0.001) was found between S-L-AP and m which was estimated with an error of 3.9 mmol Ca/day. The AP activity in the supernatant showed no significant correlation to m (r=0.11,P>0.50). The highest correlation coefficient (r=0.81,P<0.001) was found between S-BGP and m which could be predicted with an error of 3.4 mmol Ca/day. S-BGP showed a closer correlation to S-L-AP (r=0.71,P<0.001) than to S-T-AP (r=0.58,P<0.01). We concluded that S-L-AP predicts bone mineralization at organ level better than S-T-AP in selected metabolic bone disorders and that the supernatant activity shows no relation to bone turnover. We find the assay easy to handle and suitable for large-scale use in the diagnosis and monitoring of metabolic bone disease.     

Chronic thromboembolic pulmonary hypertension: surgical treatment with thromboendarterectomy

Background and objectivesPulmonary thromboendarterectomy (PTE) is considered the potential curative treatment for chronic thromboembolic pulmonary hypertension (CTEPH). We analysed the results of the PTE application in our institution.Patients and methodsFrom February 1996 to December 2007, 30 patients with CTEPH underwent videoassisted PTE. Preoperative hemodynamic data were: systolic pulmonary artery pressure (SPAP) 87±17 mmHg, mean pulmonary artery pressure (MPAP) 51±11 mmHg, pulmonary total resistance 1067±485 dynes·s·cm^?5, pulmonary vascular resistance 873±389 dynes·s·cm^?5 and cardiac index 2.2±0.5 l/min/m². We analysed the influence of several factors on hospital mortality and survival, and we performed partial analysis of mortality since 2004.ResultsPTE resulted in significant improvements in SPAP (P<0.001), MPAP (P=0.001) and cardiac index (P<0.001). Hospital mortality was 17% (5/30) (95% confidence interval, 6%-35%). From 2004, it dropped to 5% (1/20) (95% confidence interval, 0%-25%). Hospital mortality was influenced by preoperative pulmonary total resistance, preoperative pulmonary vascular resistance, postoperative SPAP, reduction of SPAP, reduction of MPAP, reperfusion pulmonary oedema and residual postoperative pulmonary hypertension (P=0.036; P=0.018;P=0.013; P=0.050; P=0.050; P=0.030; P=0.045). Survival after PTE, including hospital mortality, was 76±9% at 10 years. Through long-term follow-up, functional status (P=0.001), 6 min walking distance (P=0.001), end-diastolic right ventricle size (P<0.001), and tricuspid regurgitation (P<0.001) significantly improved.ConclusionsPTE effectively reduces pulmonary hypertension and offers CTEPH patients a substantial improvement in survival and quality of life.     

Evaluation of lithogenic elements in urine of healthy newborns

The determination of urinary excretion of lithogenic elements in healthy newborns involves factors ranging from urine collection and data handling to maternal influences, which can cause difficulties in analyzing the results. The objective of this study was to determine normal values of parameters related to lithogenesis, such as calcium, uric acid, citrate, and oxalate, in urine of healthy newborns using isolated samples, focusing on variations according to gender, weight, milk ingestion, and family history of lithiasis. Parameters measured in isolated urine samples from 104 healthy newborns (77 males and 27 females) were corrected by creatinine. The ratios were expressed as milligram/milligram of creatinine: calcium/creatinine of 0.10±0.01 (X±SE), uric acid/ creatinine of 1.10±0.10, citrate/creatinine of 0.56±0.04, and oxalate/creatinine of 0.07±0.01. Differences were observed between males and females, in terms of uric acid (0.80±0.07 vs. 1.10±0.10 mg/mg, P<0.05), citrate (0.05±0.06 vs. 0.17±0.05, P<0.05), sodium (0.17± 0.01 vs. 0.05±0.01, P<0.001), and potassium (0.05± 0.01 vs. 0.20±0.02, P<0.001). Interestingly, the urinary concentration of protector factors such citrate and potassium was higher in females than in males with low sodium excretion. Artificial milk feeding leads to higher calcium (0.10±0.06 vs. 0.06±0.01), uric acid (1.40±0.20 vs. 0.90±0.09, P<0.05), citrate (0.90±0.09 vs. 0.50±0.04, P<0.001), and oxalate (0.17±0.03 vs. 0.05±0.01, P<0.001) excretion when compared with breast feeding. There was higher excretion of calcium and sodium in patients under 3 kg. Children with familial antecedents presented some differences in urinary excretion, with higher uric acid (1.50±0.30 vs. 0.80±0.08, P<0.05) but lower calcium (0.05±0.02 vs. 0.10±0.01, P<0.05) and sodium (0.15±0.02 vs. 0.20±0.02, P<0.05) excretion, respectively. This report provides urinary parameters obtained in healthy newborns and correlates them with factors that could be involved in the genesis of osteopenia, renal stones, and/or nephrocalcinosis. Received: 8 May 2000 / Revised: 7 June 2001 / Accepted: 12 June 2001     

Prevalence and seasonal variation of hypovitaminosis D and its relationship to bone metabolism in community dwelling postmenopausal Hungarian women

Hypovitaminosis D can result in low bone mass. The prevalence of hypovitaminosis D has public health implications, especially where data are lacking. Since diet and sunlight are the two souces of vitamin D, the results obtained in one geographical region may not be universally applicable. The aim of this study is to characterize the prevalence and seasonal variation of hypovitaminosis D and its relationship to bone metabolism in community dwelling postmenopausal Hungarian women. We determined serum levels of 25-hydroxyvitamin D (25-OH-D), PTH, osteocalcin (OC), degradation products of C-terminal telopeptides of type-I collagen (CTx), dietary calcium intake and BMD at L2–L4 lumbar spine (LS) and femur neck (FN) in 319 randomly selected ambulatory postmenopausal women. The prevalence of hypovitaminosis D (serum 25-OH-D50 nmol/l) was 56.7%. On comparing patients with normal and low 25-OH-D, a significant difference was found in age (61.6±8.5 years versus 67.3±9.9 years; P<0.001), PTH (3.9±1.9 pmol/l versus 4.3±2.7 pmol/l; P<0.05), FN BMD (0.802±0.123 g/cm² versus 0.744±0.125 g/cm²; P<0.001) and dietary calcium intake (714.4±199.4 g/day versus 607.9±233 g/day; P<0.001). Osteoporotic patients had a significantly lower 25-OH-D (37.6±19.8 nmol/l versus 56.4±24 nmol/l; P<0.001) and dietary calcium intake (519.2±244.5 mg/day versus 718.2±164.3 mg/day; P<0.001). After controlling for all other variables, 25-OH-D was found to be significantly associated with age, the average hours of sunshine in the 3 months prior to 25-OH-D level determination and dietary calcium intake (r ²=0.190; P<0.001). For FN BMD, significant independent predictors were age, body mass index, 25-OH-D and dietary calcium intake (r ²=0.435; P<0.001). The prevalence of hypovitaminosis D during spring, summer, autumn and winter was 71%, 46.3%, 49.4% and 56.7%, respectively. There was significant seasonal variation in 25-OH-D, PTH, OC, calcium intake and FN BMD. There is a high prevalence of hypovitaminosis D in healthy postmenopausal Hungarian women, and FN BMD is associated with serum 25-OH-D and dietary calcium intake.     

Effect of aging on salt sensitivity of blood pressure in patients with essential hypertension

Background. Aging is considered to modulate the salt sensitivity of blood pressure (BP), but its mechanisms have not been precisely elucidated. We investigated aging-related changes in salt sensitivity and their mechanisms in patients with essential hypertension. Methods. A high-sodium (Na, 250 mEq/day, for 6 days) diet was given to 32 essential hypertensive patients of different ages (younger, aged <30 years, n = 8; middle-aged, 30–50 years, n = 10; older, ≥50 years, n = 14) after they had had a low-Na diet (25 mEq Na/day) for 3 days. Cardiac output was measured by dye-dilution, and forearm blood flow (FBF) and venous volume (VV40) by strain-gauge plethysmography. Results. The Na-induced rise in mean BP increased with age (3.2 ± 2.0%; 6.9 ± 2.1%; and 11.7 ± 1.4% respectively, in the younger, middle-aged, and older groups, and this was accompanied by a salt-induced rise in cardiac index and FBF. VV40 decreased with the high-Na diet in older hypertensives (−15.7 ± 6.1%) and the change was significantly less (P < 0.05) than in the younger group (9.3 ± 9.0%). Conclusion. The enhanced salt sensitivity of BP that occurs with aging in patients with essential hypertension is due to increased cardiac output, probably through a venous constriction-related elevation of venous return. Received: May 6, 1998 / Accepted: July 17, 1998     

Urinary calcium excretion in healthy school children

Two hundred and twenty Argentinian primary school children (122 boys, 98 girls, aged 6 – 13 years) were studied to establish reference values of 24-h urinary calcium excretion (UCa) and calcium/creatinine ratio (Ca/Cr) in 24-h urine collections and in first-morning urine samples. Mean UCa excretion was 2.05±1.40 mg/kg per day and the 95th percentile was 4.74 mg/kg per day. UCa excretion was higher in boys than girls (2.33±1.47 and 1.70±1.24 mg/kg per day respectively, P <0.001). Statistically significant differences were found between the 6- to 9-year and the 10- to 13-year age groups (2.37±1.49 vs. 1.73±1.25 mg/kg per day, P <0.001). Mean Ca/Cr ratios in 24-h collections and in first-morning urine samples were 0.129±0.086 and 0.105±0.079 for the group overall (P <0.001). The Ca/Cr ratio in the first-morning urine sample correlated poorly with the 24-h calcium excretion, suggesting that the Ca/Cr ratio in first-morning urine samples cannot replace the 24-h measurement. Received December 22, 1995; received in revised form June 17, 1996; accepted June 18, 1996     

Salt and Fluid Intake in the Development of Hypertension in Peritoneal Dialysis Patients

Background. Although fluid overload contributes to hypertension in CAPD patients, less attention has been paid to the role of excess salt and fluid intake. Therefore, we investigated the role of salt and fluid intake in the development of hypertension in CAPD patients. Methods. A total of 165 stable CAPD patients were included into this study. Based on the blood pressure in three consecutive months, they were divided into three groups: persistent hypertensive (PH; n = 33), intercurrent hypertensive (IH; n = 58) and persistent normotensive (PN; n = 74). The IH group was further divided into two phases: normotensive and hypertensive. Fluid status was evaluated by clinical assessment and bioimpedance analysis (BIA). Results. There were no differences in age, gender, and duration of dialysis among groups. Patients were more fluid overloaded in the PH group. Extracellular water (ECW), total body water (TBW), and normalized extracellular water by height (NECW) were higher in the PH group than the PN group (16.77 ± 3.62 L vs. 14.61 ± 2.92 L for ECW, p < 0.01; 32.22 ± 8.23 L vs. 28.98 ± 6.00 L for TBW, p < 0.05; and 10.28 ± 1.86 L/m vs. 9.08 ± 1.63L/m for NECW, p < 0.01). However, patients in the PH group also had more total fluid removal (TFR) and total sodium removal (TSR) compared with the PN group (1346.82 ± 431.27 mL/d vs. 1139.28 ± 412.65 mL/d for TFR, p < 0.05; and 141.52 ± 61.57 mmol/d vs. 102.42 ± 62.51 mmol/d for TSR, p < 0.01). The same trend was demonstrated when compared values of hypertensive and normotensive phase in IH group; patients had higher ECW, TBW, NECW, TSR, and PNa when they were in hypertensive phase than in the normotensive phase. Conclusions. This study confirmed that fluid overload was closely associated with the development of hypertension in CAPD patients. It also showed that hypertensive patients were in general more fluid overloaded despite a higher fluid and sodium removal as compared with normotensive patients.     

Calcium,vitamin D-endocrine system,and parathyroid hormone in black and white males

Summary The serum and urinary calcium, 25-hydroxyvitamin D (25OHD), 1,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃), and parathyroid hormone (PTH) were studied in healthy black and white males living in Belgium, and the results were compared to data in blacks of similar age living in Za?re. Dietary calcium and vitamin D were estimated in a subsample of blacks and whites examined in Belgium. Compared to whites (9.51±0.28 mg%) serum calcium was somewhat lower in blacks (9.26±0.27 mg% in Belgium; 9.19±0.48 mg% in Za?re). The 24 hour urinary calcium excretion averaged 215.0±16.7 mg% in whites and was higher (P<0.05 or less) than in blacks (115±71 mg% in Belgium; 36±33 mg% in Za?re). The serum 25OHD levels were similar in whites and blacks evaluated in Za?re, both being higher (P<0.05 or less) than in blacks living in Belgium. In the latter blacks, an inverse correlation was observed between the 25OHD level and the duration of the stay in a temperate climate. Parathyroid hormone levels were slightly higher in blacks living in Belgium than in the other two groups of subjects. The serum levels of 1,25(OH)₂D₃ and human vitamin D-binding protein were similar in the three groups of subjects. Dietary calcium averaged 541±152 mg/day in blacks and was significantly (P<0.001) less than in whites (1,203±508 mg/day), whereas no significant difference was observed in dietary vitamin D intake between blacks and whites. It is concluded that calcium intake is low in blacks but stimulation of parathyroid hormone and 1,25(OH)₂D₃ required to achieve normocalcemia does not occur.     

Habitual dietary calcium intake and cortical bone loss in perimenopausal women: A longitudinal study

Summary During an 8-year follow-up study, the effect of habitual dietary calcium intake on cortical bone loss in 154 healthy perimenopausal women was examined. Dietary calcium intake, determined by the cross-check dietary history method, and cortical bone mineral content of the radius were measured annually. Habitual dietary calcium intake was calculated as the mean of the estimated daily dietary calcium intake during the follow-up period. The women were classified according to their habitual calcium intake: those with an intake below 800 mg/day (n=28), between 800 and 1350 mg/day (n=95), and above 1350 mg/day (n=31). The results show a continuous significant loss of cortical bone in all groups, amounting yearly to 1.3±0.25, 1.5±0.10, and 1.9±0.23% (mean±SE) for the groups with a low, medium, and high habitual calcium intake, respectively (P<0.01). The differences among the three groups did not reach statistical significance (P=0.11). Body mass index was found to be positively correlated with the negative changes in cortical bone mineral density (r=0.32,P<0.01), even after adjustments had been made for confounding factors. It is concluded that a habitual calcium intake exceeding 800 mg/day (the current Recommended Daily Allowance for adults) is ineffective in preventing cortical bone loss during early menopause. Body mass index is of major importance for the perimenopausal bone loss.     

Calcium Supplementation Suppresses Bone Resorption in Early Postmenopausal Women

In order to establish whether calcium supplementation suppresses bone resorption in early postmenopausal women and whether any response is related to calcium absorption status, we studied 22 healthy women (median age 52 years) all within 5 years of the menopause. Urine was collected between 9.00 p.m. and 9.00 a.m., and 9.00 a.m. and 9.00 p.m., (2 days) and a fasting blood and spot urine sample was obtained at 9 a.m. On the first day, 5 μCi of ⁴⁵Ca in 250 ml water with 20 mg calcium carrier as the chloride was given at 9.00 a.m. and a further blood sample was obtained at 10.00 a.m. to measure calcium absorption. A 1 g calcium load was given at 9.00 p.m., immediately before the second 24-hour urine collection. There was a rise in plasma ionized calcium (1.18 ± 0.010 mmol/liter versus 1.21 ± 0.011 mmol/liter, P < 0.01) and a fall in plasma PTH (4.2 ± 0.34 pmol/liter versus 3.5 ± 0.31 pmol/liter, P < 0.01) from baseline after the calcium load, and a trend for the magnitude of the change in PTH to be inversely related to calcium absorption (r =−0.33, P= 0.13). In the fasting spot urine samples, there were falls in hydroxyproline (OHPr/Cr; 14.6 ± 0.71 versus 12.6 ± 0.83, P < 0.001), pyridinoline (Pyr/Cr; 75 ± 2.8 versus 70 ± 3.5, P < 0.05), and deoxypyridinoline (Dpd/Cr; 22.7 ± 1.2 versus 19.5 ± 1.1, P < 0.005) after the calcium load. The calcium load suppressed urinary Dpd/Cr between 9.00 p.m. and 9.00 a.m. (P < 0.005), but not between 9.00 a.m. and 9.00 p.m. We conclude that acute administration of a 1 g calcium load suppresses bone resorption in early postmenopausal women, probably by decreasing PTH secretion. Received: 2 December 1996 / Accepted: 21 May 1997     

Milk Yield and Composition,Nutrition, Body Conformation Traits,Body Condition Scores,Fertility and Diseases in High‐Yielding Dairy Cows – Part 1

Twenty‐nine pairs of high‐yielding dairy cows (HC; ≥45 kg/day reached at least once during lactation) and corresponding control cows (CC; with milk yields representing the average yield of the herds) were examined on 29 Swiss farms from March 1995 to September 1996. The hypotheses were tested that there are differences in feed intake, body‐conformation traits, body weight (BW), body condition score (BCS), fertility status and disease incidence between HC and CC cows. Cows were studied 2 weeks before and at 5, 9, 13, 17 and 40 weeks post‐partum. HC cows produced more energy‐corrected milk (ECM) than CC cows (10 670 ± 321 kg in 293 ± 5 days and 8385 ± 283 kg in 294 ± 4 days, respectively; P ≤ 0.001) and yields in the first 100 days of lactation were greater in HC than in CC cows (46.2 ± 1.1 and 36.2 ± 1.0 kg ECM/day, respectively; P ≤ 0.001). Concentrate intake was greater (P ≤ 0.05) in HC than in CC cows (7.6 ± 0.5 and 5.7 ± 0.5 kg/day, respectively) and dry matter intakes (measured in week 5 of lactation over 3 days on six farms) were greater in HC than in CC cows (24.0 ± 1.1 and 20.3 ± 1.1 kg/day, respectively; P ≤ 0.001). HC cows were taller than CC cows (wither heights 143.3 ± 0.8 and 140.1 ± 0.8 cm, respectively; P ≤ 0.01). Although BW in HC cows was greater than in CC cows throughout the study, differences and decreases of BW during lactation were not significant. BCS at the end of pregnancy and decrements during lactation were similar in HC and CC cows. Fertility parameters were similar in HC and CC cows. Incidences of mastitis, claw and feet problems, hypocalcemia/downer cow syndrome, ovarian cysts and abortions were similar in HC and CC cows, but there were more indigestion problems in HC than in CC cows.