Relation between low calcium intake, parathyroid hormone, and blood pressure

Relationship between dietary sodium, potassium, and calcium, anthropometric indexes, and blood pressure in young and middle aged Korean adults

Epidemiological evidence of the effects of dietary sodium, calcium, and potassium, and anthropometric indexes on blood pressure is still inconsistent. To investigate the relationship between dietary factors or anthropometric indexes and hypertension risk, we examined the association of systolic and diastolic blood pressure (SBP and DBP) with sodium, calcium, and potassium intakes and anthropometric indexes in 19~49-year-olds using data from Korean National Health and Nutrition Examination Survey (KNHANES) III. Total of 2,761 young and middle aged adults (574 aged 19~29 years and 2,187 aged 30~49 years) were selected from KNHANES III. General information, nutritional status, and anthropometric data were compared between two age groups (19~29 years old and 30~49 years old). The relevance of blood pressure and risk factors such as age, sex, body mass index (BMI), weight, waist circumference, and the intakes of sodium, potassium, and calcium was determined by multiple regression analysis. Multiple regression models showed that waist circumference, weight, and BMI were positively associated with SBP and DBP in both age groups. Sodium and potassium intakes were not associated with either SBP or DBP. Among 30~49-year-olds, calcium was inversely associated with both SBP and DBP (P = 0.012 and 0.010, respectively). Our findings suggest that encouraging calcium consumption and weight control may play an important role in the primary prevention and management of hypertension in early adulthood.

Inflammation in aging part 1: physiology and immunological mechanisms

During the aging process, remodeling of several body systems occurs, and these changes can have a startling effect upon the immune system. The reduction in sex steroids and growth hormones and declines in vitamin D concentration that accompany the aging process are associated with increases in the baseline levels of inflammatory proteins. At the same time, inflammation arising from atherosclerosis and other chronic diseases further contributes to the inflammatory milieu and effects a state of chronic inflammation. This chronic inflammation, or ''inflammaging'' as it has been termed, seems to be associated with a host of adverse effects contributing to many of the health problems that increase morbidity and decrease both quality of life and the ability to maintain independence in old age. For nurses to be truly informed when caring for older people and to ensure that they have a detailed understanding of the complexities of older people's health needs, they must have a knowledge of the physiological and immunological changes with age. This is the first of a two-part article on inflammatory processes in aging. These age-related changes are presented here, including an examination of the impact of genetic and lifestyle factors. The effect of these changes on the health of the individual and implications for practice are described in Part 2.

Dietary supplementation by older adults in southern China: a hospital outpatient clinic study

BACKGROUND

There has been little knowledge about dietary supplementation by the Chinese elderly. The aim of this cross-sectional study was to investigate the usage of dietary supplements by older adults in southern China.

METHODS

A total of 600 community-dwelling older adults were recruited from the outpatient clinics of three major hospitals in Foshan city between July 2007 and July 2008. Face-to-face interviews of participants were conducted to obtain information on demographics, lifestyle and dietary supplements use. Frequency and duration of usage were recorded for six categories of dietary supplements.

RESULTS

Among the 446 consented participants (241 men and 205 women) who were over 55 years of age, 19.1% consumed one or more types of dietary supplements. The prevalence of usage was significantly higher (p = 0.008) for females (24.4%) than for males (14.5%). Dietary supplements were more likely to be consumed by non-smokers (p = 0.021) and those with hyperlipidemia (p = 0.003). The most popular supplement among users was calcium (53%). The majority (71%) of the users consumed supplements on a regular basis at one or more times per day, with an average duration of 2.95 (SD 4.80) years.

CONCLUSION

The overall prevalence of dietary supplementation in this older Chinese population was considerably lower than those in other Asia-Pacific countries.

Can moderate elevations of parathyroid hormone acutely increase risk for ischemic cardiac arrhythmias?

There is suggestive evidence that chronic elevations of parathyroid hormone (PTH), associated with poor vitamin D status or low calcium intake, can increase risk for insulin resistance, weight gain, hypertension, and left ventricular hypertrophy, while stimulating production of acute phase reactants. New evidence that elevated PTH is prognostic for increased vascular mortality in very elderly subjects, prompts an examination of the possible impact of PTH on risk for arrhythmias. The cardiac effects of PTH are mediated by G protein-coupled receptors that activate phospholipase C (PLC). Catecholamines, angiotensin II, and endothelin have been shown to be arrhythmogenic for ischemic myocardium in animal studies; the receptors mediating this effect are all likewise linked to activation of PLC. Thus, it is reasonable to presume that a sufficient concentration of PTH can be arrhythmogenic in the ischemic heart. The extent to which this effect can be evoked by the high-normal PTH levels prevalent in many elderly subjects, can be assessed in epidemiological studies.

Dietary intake, blood pressure and osteoporosis

Both hypertension and osteoporosis have common underlying nutritional aetiology, with regards to dietary cations intake. We tested the hypothesis that sodium intake reflected in urinary Na/Cr and blood pressure would be negatively associated with bone mineral density (BMD), whereas other cations may have opposite associations. Subjects were part of a study of bone health in 4000 men and women aged 65 years and over. A total of 1098 subjects who were not on antihypertensive drugs or calcium supplements and who provided urine samples were available for analysis. Logistic regression was used to examine associations between total hip and lumbar spine BMD, age, gender, body mass index (BMI), urinary Na/Cr, K/Cr, calcium and magnesium intake, systolic blood pressure and diastolic blood pressure. Total hip BMD was inversely associated with age, being female and urinary Na/Cr, and positively associated with BMI, urine K/Cr and dietary calcium intake. Lumbar spine BMD was inversely associated with being female and urinary Na/Cr, and positively associated with BMI, dietary calcium intake and SBP. We conclude that sodium intake, reflected by urinary Na/Cr, is the major factor linking blood pressure and osteoporosis as shown by the inverse relationship with BMD. The findings lend further emphasis to the health benefits of salt reduction in our population both in terms of hypertension and osteoporosis.

Parathyroid hormone and the risk of incident hypertension

OBJECTIVE

The presence of parathyroid hormone receptor mRNA in a wide variety of tissues, including the endothelium, suggests that parathyroid hormone has potentially important effects in addition to the maintenance of calcium and phosphate homeostasis. We conducted a prospective study to examine the association between plasma intact parathyroid hormone levels and the subsequent risk of developing hypertension.

METHODS

We measured intact parathyroid hormone in 481 men without hypertension from the Health Professionals Follow-up Study. During 10 years of follow-up, we observed 142 cases of incident hypertension. Cox proportional hazards regression was used to adjust for age, race, body mass index, alcohol use, smoking, physical activity, predicted plasma 25-hydroxyvitamin D level, and other factors.

RESULTS

Median baseline levels of intact parathyroid hormone were 40.1 pg/ml in individuals who developed hypertension and 36.3 pg/ml in those who did not (P = 0.01). After multivariate adjustment, the relative risk for incident hypertension in men in the highest quartile of parathyroid hormone (median 56.0 pg/ml) compared with the lowest quartile of parathyroid hormone (median 26.3 pg/ml) was 1.83 (95% confidence interval 1.10-3.03; P for trend = 0.01). Analyses restricted to men in the lowest 90th percentage of the parathyroid hormone distribution (< or =58 pg/ml) yielded similar results. Further adjustment for the intake of calcium and sodium, as well as for season and fasting status at time of blood draw, did not materially change the results.

CONCLUSION

Plasma levels of intact parathyroid hormone, even within ranges considered normal, are positively and independently associated with a higher risk of incident hypertension.

Serum parathyroid hormone is associated with carotid intima-media thickness in postmenopausal women

OBJECTIVES

To test whether parathyroid hormone (PTH) might be related to the development of atherosclerosis in postmenopausal women, we measured serum levels of PTH, the carotid intima-media thickness (IMT), and other clinical and biochemical parameters.

METHODS

One hundred and seven postmenopausal women were recruited for this study. The serum level of PTH was measured by immunoradiometric assay, and carotid IMT was measured with high resolution B-mode ultrasonography.

RESULTS

On the basis of bivariate correlation analyses or unpaired t-tests, the body mass index (BMI), waist circumference, estimated glomerular filtration rate, and 25-hydroxyvitamin D were not associated with carotid IMT. In contrast, age (r = 0.414, p < 0.001), serum level of PTH (r = 0.304, p = 0.001), hypertension (p < 0.001), and hypercholesterolaemia (p = 0.004) were related to carotid IMT. On the basis of multiple regression analysis, the serum level of PTH (beta = 0.198, p = 0.029), as well as age (beta = 0.309, p = 0.001) and hypertension (beta = 0.262, p = 0.006), were independent predictors of carotid IMT.

CONCLUSIONS

Our results have demonstrated that serum PTH is an independent determinant of carotid IMT in postmenopausal women. This result suggests that serum PTH, even in the reference range, might be associated with the development of atherosclerosis or cardiovascular diseases in postmenopausal women. Further study is necessary in males and premenopausal women to fully elucidate the clinical significance of this finding.

Relation of 25-hydroxyvitamin D and parathyroid hormone levels with metabolic syndrome among US adults

OBJECTIVE

Previous research on the combined association of 25-hydroxyvitamin D (25(OH)D) and parathyroid hormone (PTH) with metabolic syndrome may have been limited by restricted age variability and a lack of representation of the general population. This study examined the combined association of 25(OH)D and PTH with Adult Treatment Panel III-defined MetSyn among a nationally representative sample of US adults.

DESIGN AND METHODS

This population-based cross-sectional study included 834 men and 820 women aged > or =20 years without diagnosed diabetes who completed a physical examination as part of the 2003-2004 US National Health and Nutrition Examination Survey.

RESULTS

After adjusting for age, sex, race/ethnicity, income, lifestyle factors, total calcium, and energy intake, the odds ratio (OR) for MetSyn in the highest quintile of 25(OH)D (median 88.0 nmol/l) compared with the lowest quintile (median 26.8 nmol/l) was 0.27 (0.15, 0.46; P(trend)<0.001). This relation was unchanged after additional adjustment for PTH level (OR, 0.26; 0.15, 0.44; P(trend)<0.001) and did not differ by sex (P interaction 0.6) or age (< or > or =50 years; P interaction 0.2). In contrast, the multivariable-adjusted odds for MetSyn increased with increasing PTH among older men (P(trend) 0.004), but not younger men (P(trend) 0.4) or women regardless of age (P(trend) 0.4 in younger and older women).

CONCLUSIONS

These data suggest an inverse association of 25(OH)D with MetSyn, independent of potential confounding factors, calcium intake, and PTH, and a positive association of PTH with MetSyn among older men.

Cross-sectional study on the relationship between body mass index and smoking, and longitudinal changes in body mass index in relation to change in smoking status: The Tromsø Study

Aims: To evaluate the effects of smoking and other lifestyle factors on body mass index (BMI), and changes in BMI in relation to changes in smoking status. Methods: A cross-sectional study was performed on 10,920 males (3937 smokers) and 12,090 females (4343 smokers) who participated in the fourth Tromsø Study (performed in 1994—95). A longitudinal study was performed on 2364 males (732 smokers in 1994—95) and 2738 females (942 smokers in 1994—95) who participated in both the fourth and the fifth Tromsø studies (performed in 2001). Results: In the cross-sectional study, current smokers of both genders had a lower BMI (25.0±3.4 vs. 25.5±3.2 kg/m2 in males, and 23.9±3.9 vs. 25.3±4.6 kg/m 2 in females, p<0.01), a lower degree of physical activity, and a higher consumption of coffee and alcohol than never-smokers. We found a U-shaped relationship between number of cigarettes smoked per day and BMI, with the lowest BMI in those smoking 6— 10 cigarettes per day. Heavy smokers and never-smokers had similar BMI. In the longitudinal study, continuing smokers had a smaller increase in BMI than those who gave up smoking. In those who gave up smoking, there was a significant, positive relationship between number of cigarettes smoked in 1994—95 and increase in BMI. Conclusions: There is a U-shaped relationship between number of cigarettes smoked per day and BMI. Smoking cessation is associated with an increase in weight as compared to those who continue smoking.

Parathyroid hormone and the cardiovascular system

The classical actions of parathyroid hormone (PTH) are well recognized, but its effects on other target tissues, such as the cardiovascular system, are less appreciated. Several studies have evaluated the effects of PTH in patients with primary hyperparathyroidism in order to understand potential cardiovascular effects in terms of hypertension, cardiovascular mortality, left ventricular function, and endothelial function. We review these studies and evaluate the cellular mechanisms that may affect these outcomes.

Vitamin D, parathyroid hormone levels, and the prevalence of metabolic syndrome in community-dwelling older adults

OBJECTIVE

Accumulating research suggests low-circulating vitamin D concentrations, i.e., 25-hydroxyvitamin-D [25(OH)D], may be associated with an increased prevalence of metabolic syndrome; however, previous studies have not accounted for parathyroid hormone (PTH) levels. We examined the association of 25(OH)D and PTH with the prevalence of metabolic syndrome in a community-based cohort of older adults.

RESEARCH DESIGN AND METHODS

Participants included 410 men and 660 women, 44-96 years old, who completed a follow-up clinic visit in 1997-1999 as part of the Rancho Bernardo Study. Sex-specific logistic regression models were fit to estimate the odds of ATP III (Adult Treatment Panel III)-defined metabolic syndrome across quintiles of 25(OH)D and PTH, adjusting for age, season, and major lifestyle factors.

RESULTS

In men, there was a significant trend (P = 0.03) of increasing adjusted odds for metabolic syndrome with increasing PTH concentrations, primarily due to an odds ratio of 2.02 (95% CI 0.96-4.24) in men in the top quintile (> or =63 ng/l) of PTH concentration. This association remained unchanged after taking into account 25(OH)D levels and excluding men with diabetes or impaired renal function; it was attenuated after adjustment for the homeostasis model assessment of insulin resistance. Neither PTH in women nor 25(OH)D levels in either sex was related to the metabolic syndrome.

CONCLUSIONS

These findings suggest an increased risk of metabolic syndrome with elevated PTH levels in older men and no effect of 25(OH)D concentrations in either sex. The reason for the sex difference in the PTH-metabolic syndrome association is unknown. Prospective studies are necessary to better determine the roles of 25(OH)D and PTH in the etiology of metabolic syndrome.

Vitamin D status and parathyroid hormone levels in relation to blood pressure: a population-based study in older men and women

BACKGROUND

Evidence is accumulating that the vitamin D endocrine system has physiological functions beyond bone health including a role in the regulation of blood pressure. Effects of poor vitamin D status on blood pressure may be mediated by elevated parathyroid hormone (PTH) levels.

AIM

To evaluate whether serum 25-hydroxyvitamin D [25(OH)D] and PTH levels are independently associated with blood pressure in a population-based study of older men and women.

METHODS

Subjects were participants of the Longitudinal Aging Study Amsterdam, aged 65 years and older. In 1205 participants, serum 25(OH)D and PTH levels were determined and diastolic and systolic blood pressure were measured. Linear and logistic regression analyses were performed with adjustments for age, sex, region, season, lifestyle factors (physical activity, smoking, alcohol intake), and waist circumference.

RESULTS

Serum 25(OH)D was not significantly associated with diastolic (beta 0.00, P = 0.98) or systolic (beta 0.06, P = 0.11) blood pressure. In contrast, higher ln-PTH levels were significantly associated with higher diastolic (beta 1.93, P = 0.03) and systolic (beta 4.67, P = 0.01) blood pressure. Higher PTH levels were associated with a substantially higher prevalence of hypertension (OR 2.00, 95% CI 1.31-3.06 for the highest versus the lowest quartile), whereas 25(OH)D showed no significant association (OR 0.89, 95% CI 0.47-1.69 for the lowest versus the highest 25(OH)D category).

CONCLUSION

These results indicate that PTH is a potentially modifiable determinant of blood pressure in the general elderly population. Serum 25(OH)D, however, was not associated with blood pressure, possibly due to the relatively high levels in our population.

Lower bone mineral content in hypertensive compared with normotensive overweight Latino children and adolescents

BACKGROUND

In adults, hypertension has been shown to be inversely correlated with bone mineral content (BMC); however, the association between blood pressure (BP) and BMC has not been studied in pediatrics.

METHODS

Total body BMC of 187 overweight (mean BMI = 28.7 kg/m(2)) Latino children and adolescents (mean age = 11.2 years) were measured using dual-energy x-ray absorptiometry. Seated systolic BP (SBP) and diastolic BP (DBP) were measured using a standard mercury sphygmomanometer. Hypertension was defined by SBP or DBP above the 90(th) percentile for height, age, and sex.

RESULTS

Partial correlations revealed an inverse association between SBP and BMC (r = -0.24, P = 0.02) in boys (n = 105); results were nonsignificant (P = 0.27) in girls (n = 82). There were no significant correlations between DBP and BMC. When BMI and insulin sensitivity were adjusted for, hypertensive boys (n = 21) had lower BMC (1435 v 1636 g; P = 0.03) than normotensive boys (n = 84); similarly, hypertensive girls (n = 25) had lower BMC (1438 v 1618 g; P = 0.02) than normotensive girls (n = 57). In postpubertal adolescents (Tanner stage 4-5; n = 48), inverse correlations were stronger (r = -0.40, P = 0.007); results were nonsignificant in prepubertal and pubertal children (Tanner stage 1-3; n = 139, P = 0.57). In postpubertal girls (n = 37), there were no significant correlations (P = 0.14); inverse correlations in postpubertal boys (n = 11) became markedly stronger (r = -0.80, P = 0.02).

CONCLUSION

Based on the study findings, SBP is inversely correlated with BMC in overweight adolescents; additionally, hypertensive subjects have lower adjusted means of BMC than normotensive subjects. These promising new findings suggest that hypertension may be a risk factor for osteopenia in overweight children and adolescents; this risk may be exacerbated in postpubertal boys.

Insulin sensitivity in subjects with secondary hyperparathyroidism and the effect of a low serum 25-hydroxyvitamin D level on insulin sensitivity

To investigate the relation between secondary hyperparathyroidism (SHPT) and insulin sensitivity, 15 subjects with SHPT (serum PTH >6.4 pmol/l, serum calcium <2.40 mmol/l, and normal serum creatinine) and 15 control subjects were investigated with an oral glucose tolerance test (OGTT) and a 3-h hyperglycemic clamp. Body composition was measured with dual-energy X-ray absorptiometry. No differences were found between the SHPT and control groups on any indices of glucose or insulin metabolism. However, when dividing the 30 subjects in the upper and lower halves according to serum 25-hydroxyvitamin D levels (<59 and >58 nmol/l), those in the lower half had significantly higher 2-h serum insulin value at the OGTT, significantly higher insulin secretion during the last hour of the clamp, and significantly lower insulin sensitivity index (ISI; glucose infusion rate/insulin secretion during the last hour of the clamp). In a multiple linear regression analysis correcting for age, gender, and body mass index (BMI), the serum 25-hydroxyvitamin D level was significantly and positively associated with the ISI. The amounts of total body and truncal fat were negatively and significantly associated with the ISI, whereas no association between measures of lean body mass were associated with insulin secretion or sensitivity.

Fat mass is an important predictor of parathyroid hormone levels in postmenopausal women

Previously, we reported that people with elevated parathyroid hormone (PTH) levels due to primary hyperparathyroidism have increased body weight compared to eucalcemic controls. We sought to determine whether the same relationship between PTH and body weight exists in eucalcemic healthy postmenopausal women, and to investigate the relationships between components of body weight, PTH, vitamin D metabolites, and metabolic indices. We performed a cross-sectional analysis of 116 healthy community-dwelling postmenopausal women. Pearson correlation analysis was used to test for univariate linear relationships between variables, and stepwise multiple regression analysis to assess for multivariate relationships. We found that PTH was significantly positively correlated with body weight, regional and total fat mass, and percent body fat, and negatively correlated with activity levels, 25 hydroxyvitamin D (25OHD), dietary calcium intake, and serum phosphate. On multivariate analysis, PTH was positively related to percent body fat (P = 0.020; partial r2 = 0.10) and negatively related to dietary calcium intake (P = 0.041; partial r2 = 0.03) and serum phosphate (P = 0.026; partial r2 = 0.04). Adjusting for vitamin D insufficiency or 25OHD levels did not affect the relationship between PTH and fat mass. For 25OHD, there were significant positive correlations with lumbar spine BMD and serum albumin, and significant negative correlations with PTH, total fat mass, trunk fat, and pelvic fat. On multivariate analysis, 25OHD was positively related to serum albumin (P = 0.008; partial r2 = 0.07) and negatively related to pelvic fat mass (P = 0.014; partial r2 = 0.05). Adjusting for PTH levels did not change the relationship between 25OHD and pelvic fat mass. We conclude that fat mass is a significant independent determinant of serum PTH levels, and that this relationship is independent of the inverse relationship between 25OHD and fat mass. This association between fat mass and PTH might contribute to the association between primary hyperparathyroidism and increased body weight.

Causes of secondary hyperparathyroidism in a healthy population: the Tromsø study

Secondary hyperparathyroidism (SHPT) develops as a compensatory mechanism when the body is in calcium deficit. SHPT may be harmful and has been associated with elevated blood pressure. The cause of SHPT could be low calcium intake, reduced intestinal calcium absorption, or increased excretion. However, the relative importance of these factors for the development of SHPT is not known. During the 5th Tromsø study, serum PTH and calcium were measured in 7954 subjects. Then 96 subjects with SHPT (defined as serum PTH above 6.4 pmol/l together with serum calcium below 2.40 mmol/l) and 106 control subjects were examined at follow-up with a food frequency questionnaire, calcium absorption test, measurement of 24-h urinary calcium excretion, and serum vitamin D status. The statistical analyses showed several interactions necessitating subgroup analysis. It was found that the calcium intake was significantly lower in the SHPT group, but only in nonsmoking males; the calcium absorption was nonsignificantly higher in the SHPT group; the serum 25-hydroxyvitamin D levels were significantly lower in the SHPT group but only in nonsmokers; and the 24-h urinary calcium excretion was significantly lower in the SHPT group but only in those not on blood pressure medication. The most frequent cause of SHPT appeared to be low calcium intake (18%) and a low serum 25-hydroxyvitamin D level (18%). However, in most subjects with SHPT all tests were within the normal range, and the cause is therefore probably a combination of several factors.

Serum parathyroid hormone as a predictor of increase in systolic blood pressure in men

BACKGROUND

In cross-sectional studies there appears to be a link between calcium metabolism and blood pressure, and most studies have found a positive association between serum parathyroid hormone (PTH) and hypertension.

OBJECTIVE

To determine the prognostic value of serum PTH regarding a future increase in blood pressure.

DESIGN

A prospective cohort study.

SUBJECTS

A total of 1784 individuals who had measurements of PTH in serum samples from both the fourth (1994) and fifth (2001) Tromsø studies, who did not use blood pressure medication during the observation period, and had serum calcium less than 2.61 mmol/l, were included.

MAIN OUTCOME MEASURE

Delta blood pressure (blood pressure from 2001 minus blood pressure from 1994).

RESULTS

The mean delta systolic blood pressure in the men and women during these 7 years was 5.8 and 8.1 mmHg, respectively. In a sex-specific linear regression model correcting for age, body mass index (BMI), and smoking status, serum PTH from 1994 was a significant predictor of delta systolic blood pressure in men (P < 0.01), but not in women. The difference in delta systolic blood pressure between those in the highest and those in the lowest PTH quartile was 3.5 mmHg. Similarly, delta serum PTH (serum PTH from 2001 minus serum PTH from 1994) was a significant predictor of delta systolic blood pressure in men (P < 0.05).

CONCLUSIONS

Although these findings do not prove a causal relationship between PTH and blood pressure, it adds to the growing number of indications that PTH is involved in the development of hypertension.

Effects of acute hypercalcaemia on blood pressure in subjects with and without parathyroid hormone secretion

AIM

Acute hypercalcaemia increases the blood pressure, but the mechanism is uncertain. It may partly be the result of the concomitant fall in parathyroid hormone (PTH) secretion as PTH has been reported to have a vasodilator effect. To elucidate this, we infused calcium intravenously in subjects with and without PTH secretion.

METHODS

Seven thyroparathyroidectomized subjects with undetectable PTH levels and 10 controls were studied twice, once with a calcium clamp technique that increased plasma ionized calcium in two steps of 0.1 mmol L(-1), each step lasting 60 min, and once with a placebo infusion.

RESULTS

On the placebo day, blood pressure and all other variables were unaffected in both groups. On the calcium day, systolic blood pressure increased gradually and significantly from end of baseline till end of the calcium infusion in the controls (123.5 +/- 19.8 and 134.2 +/- 17.6 mmHg, P < 0.004) but not in the thyroparathyroidectomized subjects (124.9 +/- 15.7 and 126.0 +/- 20.6 mmHg, P = ns). Serum PTH levels fell promptly in the controls, and in both groups there was a significant increase in serum phosphate. The diastolic blood pressure and pulse rate, and the plasma adrenaline and noradrenaline, plasma renin activity, and serum aldosterone levels were unaffected by the calcium infusion.

CONCLUSION

During acute hypercalcaemia the blood pressure increase appears unrelated to catecholamine secretion and the renin-aldosterone system, whereas the fall in PTH secretion may play a contributory role.

Etiology and management of hypertension in chronic kidney disease

The kidneys are vital in the pathogenesis of hypertension and are also pathologically affected by the presence of hypertension. The prevalence of hypertension in chronic kidney disease (CKD) depends on age, the severity of renal failure, and proteinuria. The intricate and inextricable relationship between CKD and hypertension seems to cause cardiovascular disease that has assumed epidemic proportions. This article discusses the etiology and treatment of hypertension in CKD so that it can be better controlled.

Association between primary hyperparathyroidism and increased body weight: a meta-analysis

Although primary hyperparathyroidism is frequently asymptomatic, it has been associated with an increased prevalence of hypertension, insulin resistance, dyslipidemia, cardiovascular mortality, and cancer. Previously we reported that patients with primary hyperparathyroidism are heavier than age-matched controls. Increased body weight could contribute to the association between primary hyperparathyroidism and these extraskeletal complications. We searched MEDLINE for English language studies published between 1975 and 2003 that reported body weight or body mass index in subjects with primary hyperparathyroidism and a healthy age- and sex-comparable eucalcemic control group. Seventeen eligible studies were identified. Subjects with primary hyperparathyroidism were 3.34 kg (95% confidence interval, 1.97-4.71; P < 0.00001) heavier than controls in 13 studies reporting body weight. In four studies reporting body mass index, subjects with primary hyperparathyroidism had an increased body mass index of 1.13 kg/m(2) (-0.29 to 2.55; P = 0.12) compared with controls. Standard mean difference analysis showed that subjects with primary hyperparathyroidism had an increased weight or body mass index of 0.3 sd (0.19-0.40; P < 0.00001) compared with controls. We conclude that patients with primary hyperparathyroidism are heavier than their eucalcemic peers, and that increased body weight may contribute to the reported associations between primary hyperparathyroidism and some extraskeletal complications.

Coeliac disease in subjects with secondary hyperparathyroidism

OBJECTIVE

Coeliac disease (CD) may present in its classical form with diarrhoea and weight loss, but also with atypical symptoms that are both related and unrelated to malabsorption. Osteomalacia or osteopenia following malabsorption of calcium and vitamin D is known to occur in patients with CD, and in such cases secondary hyperparathyroidism (SHP) caused by low serum calcium levels is frequently found. However, the prevalence of CD in subjects with SHP has not been reported.

MATERIAL AND METHODS

In the Tromsø study 2001, serum parathyroid hormone (PTH) and calcium were measured in 7954 subjects of whom 6061 were eligible for follow-up. From this group, 97 subjects with SHP (serum PTH> or =6.5 pmol/l and serum calcium <2.40 mmol/l) and 104 matched control subjects were re-examined with serological tests for CD (anti-tissue transglutaminase, anti-gluten IgA and IgG).

RESULTS

CD was diagnosed in 4 subjects, all from the original SHP group. At the re-examination, only 29 of the 97 subjects with SHP still had elevated serum PTH levels. Among these were 3 of the subjects with CD. When grouping the serological test results as negative, borderline or positive, there was a significant difference between the SHP group and the controls for anti-tissue transglutaminase and anti-gluten IgA (p<0.05).

CONCLUSIONS

Subjects with SHP, at least when SHP is persistent, should be tested for CD.

Same-day discharge after total thyroidectomy: The value of 6-hour serum parathyroid hormone and calcium levels

BACKGROUND

The purpose of this study was to determine whether patients who undergo total thyroidectomy will have postoperative hypocalcemia develop when they reach the critical 6-hour serum levels defined as parathyroid hormone (PTH) > or =28 ng/L and simultaneous corrected calcium > or =2.14 mmol/L.

METHODS

This was a prospective study involving 70 consecutive total thyroidectomy patients. There were 51 women and 19 men involved in the study. The mean age was 49.3 years (range, 21-76 years). Patients who had completion thyroidectomy or neck dissections were excluded. Patients undergoing parathyroidectomy at the time of thyroidectomy were also excluded. PTH and corrected calcium levels were measured postoperatively at 6, 12, and 20 hours.

RESULTS

Hypocalcemia developed in 24% (17 of 70) of the patients. Of the 53 patients who remained normocalcemic, 68% (36 of 53) reached the 6-hour critical level. None of the hypocalcemic patients (0 of 17) attained the 6-hour critical level (chi-square test p < .0001). This translates into a specificity of 100% (95% confidence interval [CI], 80.5% to 100%) and a positive predictive value of 100% (95% CI, 90.1% to 100%).

CONCLUSIONS

The simultaneous evaluation of PTH and corrected calcium levels 6 hours after thyroidectomy allows for an accurate prediction of the trend of serum calcium. This study enables us to confidently consider same-day discharge for most of our thyroidectomy patients.

The effect of nutrient profiles of the Dietary Approaches to Stop Hypertension (DASH) diets on blood pressure and bone metabolism and composition in normotensive and hypertensive rats

Hypertension has been associated with abnormalities of Ca and bone metabolism. Consequently, dietary strategies aimed at reducing blood pressure may also benefit bone health; however, this issue has received little attention. Therefore, the objective of the present study was to investigate the effect of two antihypertensive-type diets on blood pressure and bone metabolism and composition in normotensive (Wistar-Kyoto NHsd, WKY) and hypertensive (spontaneously hypertensive NHsd, SHR) rats. Thirty WKY and thirty SHR male rats, 14 weeks old, were separately randomized by weight into three groups of ten rats each. One group from each strain was given a control diet while the other two groups were fed two anti-hypertensive (high fruit and vegetable (F/V) and high fruit and vegetable and low-fat dairy produce (combination)) diets for 8 weeks. SHR rats were significantly (P<0.01) heavier than WKY rats. Blood pressure and femoral length, width, dry weight, ash, Ca, Mg, P and bone mineral mass were significantly (P<0.0001) greater in SHR than WKY rats, but were unaffected by diet, irrespective of strain. While markers of bone formation (serum osteocalcin) and bone resorption (urinary pyridinoline and deoxypyridinoline) were similar in both strains, these markers were significantly (P<0.05) lower (28-31, 16-23, 31-33 % respectively) in the SHR rats fed the combination diet relative to those fed the control and F/V diets. Bone turnover in WKY rats was unaffected by diet. In conclusion, these findings suggest that the combination diet may benefit bone metabolism in hypertensive animals. However, as blood pressure was unaffected by this diet, the mechanism by which it reduced bone turnover requires further investigation.

Effect of calcium supplementation on blood pressure in patients with secondary hyperparathyroidism

The aim was to study the effect of calcium supplementation 477 mg twice daily on BP in patients with secondary hyperparathyroidism during an intervention study (6 weeks) and after 954 mg during a short study (3 h). The intervention study was a placebo-controlled, double-blind, cross-over, while the short study gave a placebo and calcium in random order on separate days. The participants were obtained from an epidemiological survey in Tromsø 1994-1995 that included more than 27.000 subjects. The re-examination was performed in 2000/2001 at the University Hospital of North Norway, Norway. There were 18 subjects with secondary hyperparathyroidism and 28 control subjects in the intervention study while there were 14 cases and 8 control subjects in the short study. The results showed that in the subjects with secondary hyperparathyroidism after calcium supplementation in the intervention study there was an increase in serum calcium from 2.28 +/- 0.09 to 2.36 +/- 0.06 mmol/l (mean +/- SD) and a decrease in serum PTH from 8.6+/-1.6 to 6.5+/-2.4 pmol/l. However, there was no significant difference in either systolic or diastolic BP between calcium supplementation and placebo (138.3 +/- 21.0 vs 135.9 +/- 17.0 mm Hg and 80.9 +/- 11.1 vs 78.9+/-9.5 mm Hg, respectively). Similar results were seen in the control group. In the short study, serum calcium increased and serum PTH decreased after oral calcium, but the BP did not differ as compared to when placebo was given. To conclude, in the present setting we did not find any effect on BP by calcium supplementation in subjects with moderate secondary hyperparathyroidism.

Intakes of calcium and vitamin d predict body mass index in the population of Northern Norway

This study was designed to investigate whether there is any association between body mass index (BMI) and life-style factors, with a special emphasis on calcium and vitamin D intakes. In 1994/1995, men (n = 9252) and women (n = 9662) participated in the fourth Tromsø study and completed the food-frequency and life-style factor questionnaires. We measured BMI, coffee and alcohol consumption, physical activity, smoking, and calcium and vitamin D intakes. A negative association between physical activity, smoking and BMI, and a positive association between BMI and coffee intake were found in both sexes (P < 0.001). BMI and calcium intake were positively related in men (P < 0.001), but not in women. BMI and vitamin D intake were negatively associated in both sexes (P < 0.001), which to our knowledge has not been reported before. The lowest quartile of vitamin D intake was an independent predictor of obesity (defined as BMI >30 kg/m(2)) in men and women (P < 0.001 in both genders), resulting in odds ratios of 2.24 [95% confidence interval (CI) 1.80, 2.80] in men and 1.51 (95% CI 1.23, 1.85) in women compared with the highest quartile. In conclusion, calcium and vitamin D intakes may have opposing effects on body weight, which is difficult to explain given current knowledge of calcium metabolism.