Vitamin D insufficiency and the blunted PTH response in established osteoporosis: the role of magnesium deficiency

Hypomagnesemia and inflammation: clinical and basic aspects

In recent years, increasing awareness of hypomagnesemia has resulted in clinical trials that associate this mineral deficiency with diabetes, metabolic syndrome, and drug therapies for cancer and cardiovascular diseases. However, diagnostic testing for tissue deficiency of magnesium still presents a challenge. Investigations of animal and cellular responses to magnesium deficiency have found evidence of complex proinflammatory pathways that may lead to greater understanding of mediators of the pathobiology in neuronal, cardiovascular, intestinal, renal, and hematological tissues. The roles of free radicals, cytokines, neuropeptides, endotoxin, endogenous antioxidants, and vascular permeability, and interventions to limit the inflammatory response associated with these parameters, are outlined in basic studies of magnesium deficiency. It is hoped that this limited review of inflammation associated with some diseases complicated by magnesium deficiency will prompt greater awareness by clinicians and other health providers and in turn increase efforts to prevent and treat this disorder.

Challenges in the differential diagnosis of hypercalcemia: A case of hypercalcemia with normal PTH level

The hypercalcemias are a common and heterogeneous group of disorders, ranging from the occasional detection of a high level of serum calcium to a life-treating condition. In a patient presenting with hypercalcemia, a differential diagnosis can be established easily by measuring serum calcium and parathyroid hormone (PTH) concentrations. We describe the case of an 83-year-old man presenting with a severe symptomatic hypercalcemia with high-normal PTH level due to the coexistence of primary hyperparathyroidism and malignancy-associated hypercalcemia. The presence of two conditions producing hypercalcemia was revealed only during in-hospital stay and after the administration of an intravenous bisphosphonate, when the PTH concentration increased rapidly after bisphosphonate treatment with a decrease in serum calcium. The occurrence of two conditions producing hypercalcemia is a rare event in the literature, and should be considered in the presence of an abnormally high serum calcium level associated with normal or high-normal PTH, in order to establish a correct diagnosis and appropriate interventions.

Nitric oxide mediates low magnesium inhibition of osteoblast-like cell proliferation

An adequate intake of magnesium (Mg) is important for bone cell activity and contributes to the prevention of osteoporosis. Because (a) Mg is mitogenic for osteoblasts and (b) reduction of osteoblast proliferation is detected in osteoporosis, we investigated the influence of different concentrations of extracellular Mg on osteoblast-like SaOS-2 cell behavior. We found that low Mg inhibited SaOS-2 cell proliferation by increasing the release of nitric oxide through the up-regulation of inducible nitric oxide synthase (iNOS). Indeed, both pharmacological inhibition with the iNOS inhibitor l-N(6)-(iminoethyl)-lysine-HCl and genetic silencing of iNOS by small interfering RNA restored the normal proliferation rate of the cells. Because a moderate induction of nitric oxide is sufficient to potentiate bone resorption and a relative deficiency in osteoblast proliferation can result in their inadequate activity, we conclude that maintaining Mg homeostasis is relevant to ensure osteoblast function and, therefore, to prevent osteoporosis.

Vitamin D and the postmenopausal population

Vitamin D, a hormone critical to the body's maintenance of serum calcium and phosphorus concentrations, is currently the subject of much scientific interest. Low levels of vitamin D have been observed in many populations and epidemiological studies have suggested a link between this biochemical state and a range of diseases, such as cancer, diabetes and multiple sclerosis. While the consequence of vitamin D deficiency is well documented for bone (rickets and osteomalacia), with mixed findings relating to falls and fractures, a causal link between vitamin D deficiency and these wider health outcomes has not been established. If these relationships were found to be causal, the morbidity and mortality resulting from low levels of vitamin D could be substantial; the current evidence base, however, most robustly supports the assessment of serum 25(OH)-vitamin D in the context of specific symptoms, low bone mineral density or biochemical abnormalities, rather than as an entity to treat in its own right or as the basis for a population-wide screening programme.

Parathyroid hormone response to vitamin D insufficiency in elderly males with chronic heart failure

Secondary hyperparathyroidism (SHPT) may contribute to the systemic illness that accompanies chronic heart failure (CHF). Healthy elderly with vitamin D deficiency who did not develop hyperparathyroidism (functional hypoparathyroidism, FHPT) had lower mortality than those who did. This study was designed to examine determinants of the PTH response in the vitamin D insufficient CHF patients. Sixty five vitamin D insufficient males with NYHA class II and III and 20 control subjects age >/=55 years were recruited. Echocardiography, physical performance, NT-pro-BNP, PTH, 25-hydroxyvitamin D (25(OH)D), adiponectin and bone activity surrogate markers (OPG, RANKL, OC, beta-CTx) were assessed. Increased NYHA class was associated with SHPT, while physical performance was inferior compared to FHPT. SHPT was associated with lower left ventricular ejection fraction (LVEF) and flow mediated dilatation, but with higher left heart dimensions, left ventricular mass index and right ventricular systolic pressure. CHF patients with SHPT had increased NT-pro-BNP, adiponectin and bone markers, but decreased 25(OH)D compared to those with FHPT. Independent determinants for SHPT in CHF patients with vitamin D insufficiency were LVEF, adiponectin and beta-CTx, irrespective of renal function and serum vitamin D levels. In conclusion, increased PTH levels, but not low vitamin D, demonstrated close relation to CHF severity.

High prevalence of low bone mineral density in patients with tropical calcific pancreatitis

OBJECTIVES

Patients with tropical calcific pancreatitis (TCP) have multiple risk factors for developing low bone mineral density (BMD). We studied BMD and serum 25-hydroxyvitamin D (25[OH]D) in north Indian TCP patients.

METHODS

In a cross-sectional study, 72 TCP patients (mean age, 31 ± 10 years) and 100 controls were studied. Serum 25(OH)D was measured in all subjects; BMD was measured by dual-energy x-ray absorptiometry in 56 adult patients and 4 children and compared with a reference Indian population.

RESULTS

Mean BMD and BMD Z-scores at the lumbar spine and total hip were significantly lower in all age groups. The BMD Z-scores at the lumbar spine and total hip were -1.0 ± 1.0 and -1.2 ± 1.2, respectively. Low bone density (Z-score ≤ -2 at ≥ 1 sites) was present in 22 (39%) adult patients and 3 of the 4 children studied. On multivariate analysis, BMD Z-scores were positively associated with body mass index and inversely with pancreatitis. Vitamin D deficiency (25[OH]D < 50 nmol/L) was equally prevalent in patients (86%) and controls (85%).

CONCLUSIONS

Despite their young age, patients with TCP have significantly low BMD. Measures to improve nutrition should be instituted in all TCP patients from an early age.

An unusual case of hypercalcemia associated with graves' disease and vitamin d deficiency

Objective:

To present a case of hypercalcemia associated with thyrotoxicosis in a patient with vitamin D deficiency and review biochemical changes during the course of treatment.

Methods:

We report a case, describe the changes in serum calcium, phosphorus, parathyroid hormone in Graves’ disease and concomitant Vitamin D deficiency. We compare our findings to those reported in literature.

Results:

Our patient had hypercalcemia secondary to thyrotoxicosis alone, which was confirmed by low parathyroid hormone level and resolution of hypercalcemia with treatment of thyrotoxicosis. The case was complicated by a concomitant vitamin D deficiency. Serum calcium elevation in patients with thyrotoxicosis occurs secondary to hyperthyroidism alone or due to concurrent hyperparathyroidism. Hypercalcemia from thyrotoxicosis is usually asymptomatic and is related to bone resorption. Vitamin D deficiency can be seen in patients with thyrotoxicosis because of accelerated metabolism, poor intestinal absorption and increased demand during bone restoration phase. Coexistence of hypercalcemia and Vitamin D deficiency in patients with thyrotoxicosis is rare, but possible, and 25-hydroxyvitamin D levels should be checked. The definite treatment for hypercalcemia in thyrotoxicosis is correction of thyroid function.

Conclusion:

Hypercalcemia in thyrotoxicosis should be distinguished from concomitant hyperparathyroidism and confirmed by resolution of hypercalcemia with control of thyrotoxicosis. Patients with hypercalcemia and thyrotoxicosis may also have vitamin D deficiency and 25-OH Vitamin D levels should be checked.

Dual effect of adipose tissue on bone health during growth

Recent studies suggest association between body fat and childhood bone health, although conflicting findings have also been reported. The aim of the present study was to examine the association between body fat content and areal BMD, volumetric BMD, bone turnover markers, and calcitropic factors in apparently healthy children and adolescents. The study was carried out as a school based cross-sectional cohort study with 186 subjects (61% girls) aged from 7 to 19 years. Background characteristics, including medical history and lifestyle factors, were collected. Anthropometry, BMD and body composition measurements with DXA and pQCT, a fasting blood sample and a second morning void urine sample were obtained. The subjects were divided into three groups, representing low, intermediate and high adiposity, based on age and gender specific fat percentage Z-scores. Multivariate analysis was performed to all bone variables using lean body mass, pubertal development, dietary intake of calcium and intensity of physical activity as covariates. In pQCT, a significant difference between the groups was observed in cortical BMD (MANOVA; p=0.02) in proximal radius, the intermediate group having the highest values. Similarly, DXA-derived LS and WB BMD Z-scores differed significantly between the groups (MANOVA; p=0.026 and p=0.036, respectively), with highest values in the intermediate group. High body fat content associated also with low bone turnover markers, low PTH, high S-Ca and high urinary calcium excretion. The differences in biochemical markers explain our and others' findings of bone health in children and adolescents with different body fat content. These findings suggest that normal body fat content is beneficial for bone health in growing children and adolescents while both low and high body fat content have adverse skeletal effects.

Vitamin D insufficiency defined by serum 25-hydroxyvitamin D and parathyroid hormone before and after oral vitamin D₃ load in Japanese subjects

Vitamin D insufficiency is a risk for both skeletal and nonskeletal health. However, some ambiguity remains about threshold serum 25(OH)D for vitamin D insufficiency. To determine the threshold serum 25(OH)D to maintain normal calcium availability without elevation in serum parathyroid hormone (PTH) among Japanese subjects with various calcium intakes, we conducted a multicenter prospective open-labeled study. We recruited 107 ambulatory subjects without disorders affecting vitamin D metabolism to whom oral vitamin D₃ 800 IU/day for 4 weeks or 1,200 IU/day for 8 weeks was given. Serum 25(OH)D, PTH, calcium, phosphate, and magnesium were measured before and after vitamin D₃ supplementation. Calcium intake was assessed by questionnaires. When all the data were combined, serum 25(OH)D was negatively correlated with PTH. The cubic spline curve between serum 25(OH)D and PTH indicated PTH reached its plateau between 35 and 40 pg/ml at 25(OH)D between 25 and 30 ng/ml. Vitamin D₃ supplementation increased serum 25(OH)D and decreased PTH. Change in PTH correlated positively with baseline serum 25(OH)D. From the regression analyses, baseline serum 25(OH)D above 28 ng/ml corresponded to the threshold level without reduction in PTH after vitamin D₃ supplementation. In multivariate regression analyses, age but not calcium intake was a significant determinant of PTH. We concluded that a serum 25(OH)D level of 28 ng/ml was identified as a threshold for vitamin D insufficiency necessary to stabilize PTH to optimal levels.

Reducing fracture risk with calcium and vitamin D

Studies of vitamin D and calcium for fracture prevention have produced inconsistent results, as a result of different vitamin D status and calcium intake at baseline, different doses and poor to adequate compliance. This study tries to define the types of patients, both at risk of osteoporosis and with established disease, who may benefit from calcium and vitamin D supplementation. The importance of adequate compliance in these individuals is also discussed. Calcium and vitamin D therapy has been recommended for older persons, either frail and institutionalized or independent, with key risk factors including decreased bone mineral density (BMD), osteoporotic fractures, increased bone remodelling as a result of secondary hyperparathyroidism and increased propensity to falls. In addition, treatment of osteoporosis with a bisphosphonate was less effective in patients with vitamin D deficiency. Calcium and vitamin D supplementation is a key component of prevention and treatment of osteoporosis unless calcium intake and vitamin D status are optimal. For primary disease prevention, supplementation should be targeted to those with dietary insufficiencies. Several serum 25-hydroxyvitamin D (25(OH)D) cut-offs have been proposed to define vitamin D insufficiency (as opposed to adequate vitamin D status), ranging from 30 to 100 nmol/l. Based on the relationship between serum 25(OH)D, BMD, bone turnover, lower extremity function and falls, we suggest that 50 nmol/l is the appropriate serum 25(OH)D threshold to define vitamin D insufficiency. Supplementation should therefore generally aim to increase 25(OH)D levels within the 50-75 nmol/l range. This level can be achieved with a dose of 800 IU/day vitamin D, the dose that was used in successful fracture prevention studies to date; a randomized clinical trial assessing whether higher vitamin D doses achieve a greater reduction of fracture incidence would be of considerable interest. As calcium balance is not only affected by vitamin D status but also by calcium intake, recommendations for adequate calcium intake should also be met. The findings of community-based clinical trials with vitamin D and calcium supplementation in which compliance was moderate or less have often been negative, whereas studies in institutionalized patients in whom medication administration was supervised ensuring adequate compliance demonstrated significant benefits.

Regulation of PTH secretion by 25-hydroxyvitamin D and ionized calcium depends on vitamin D status: a study in a large cohort of healthy subjects

INTRODUCTION

Previous papers investigating vitamin D status have often outlined the significant relationships between serum parathyroid hormone (PTH) and 25-hydroxyvitamin D (25OHD), but the influence of ionized calcium levels has not been concomitantly considered.

DESIGN

Cross-sectional.

MATERIALS AND METHODS

In 1050 healthy men (547) and women (503), serum ionized calcium (iCa), creatinine (Cr), albumin, 25OHD, and PTH were measured. After conventional analysis, a regression tree was fitted on the data set.

RESULTS

25OHD and PTH values showed significant opposite seasonal changes. 25OHD levels negatively correlated with PTH, which in turn negatively correlated with iCa. A regression tree was fitted to the whole data set using PTH as the response variable and 25OHD and iCa as covariates. PTH concentration depended on that of iCa only in subjects with 25OHD levels>16.35 ng/mL, while for 25OHD<16.35 ng/mL it depended on 25OHD values.

CONCLUSIONS

Our results indicated that PTH levels were highly conditioned by those of 25OHD in subjects with 25OHD values lower than 16.35 ng/mL and by those of iCa only for higher 25OHD concentration.

Hip fracture type: important role of parathyroid hormone (PTH) response to hypovitaminosis D

OBJECTIVE

To investigate whether clinical and laboratory characteristics, including serum 25-hydroxyvitamin D (25(OH) D), PTH and parameters of mineral and bone metabolism, differ by hip fracture (HF) type.

PATIENTS AND METHODS

We studied prospectively 761 consecutively admitted older patients (mean age 82.3+8.8(SD) years; 74.9% women) with low trauma non-pathological HF. A detailed clinical examination was performed, haematologic, renal, liver and thyroid function tests, serum 25(OH)D, PTH, calcium, phosphate, magnesium, C-reactive protein (CRP) and cardiac troponin I (cTnI) measured. In a subset of 294 patients' markers of bone formation (serum osteocalcin, OC; bone specific alkaline phosphatase, BAP) and bone resorption (urinary deoxypyridinoline, DPD/Cr; N-terminal cross-linked telopeptide of type 1 collagen, NTx/Cr; both corrected to urinary creatinine, Cr) were also measured.

RESULTS

In the trochanteric compared to the cervical group, females were older than males and the prevalence of Parkinson's disease, mean haemoglobin and albumin levels were lower. Incidence and degree of myocardial injury (cTnl rise) and inflammatory reaction (CRP elevation) as well as length of hospital stay, need of institutionalisation or in-hospital mortality were similar in both groups. Hypovitaminosis D (25(OH)D <50 mmol/L) was present in 77.8% of patients with cervical and in 82.1% with trochanteric HF, elevated PTH (>6.8 pmol/L) in 30.2% and 41.3%, respectively. The associations between 25(OH)D, PTH, and parameters of mineral metabolism and bone turnover were site-specific. In multivariate analyses, PTH (both as a continuous or categorical variable) response to hypovitaminosis D was a strong independent predictor of HF type. Coexistence of vitamin D deficiency (25(OH) D< 25 nmol/L) and elevated PTH predicts trochanteric HF while blunted PTH response predicts cervical HF (OR=3.5; 95% CI 1.5-80; p=0.005). PTH response and phosphate status (above or below median level) correctly discriminated HF type in 73.8% of patients with vitamin D deficiency.

CONCLUSIONS

HF type is significantly associated with PTH response to hypovitaminosis D and impaired phosphate homeostasis. We detected only minor differences between two main HF types with regard to a wide range of clinical and routine laboratory variables as well as short-term outcomes.

Bariatric surgery and bone metabolism: a systematic review

Few studies have demonstrated the risk of metabolic bone disease and a reduction in bone mineral density (BMD) after bariatric surgery. A systematic review was conducted of case-control and cohort studies with the aim of evaluating the relationship between bariatric surgery and bone metabolism. The search was undertaken in MedLine, covering the period from January 1997 to August 2009, using the keywords: "bariatric surgery" AND "osteoporosis", "fracture", "bone diseases", "metabolic". Six studies were included, comprising four cohort and two case-control studies. Three studies evaluated bone metabolism and BMD, and the other evaluated bone metabolism only. Based on this review, bariatric surgery is associated with alterations in bone metabolism, loss of bone mass and an increased risk of fracture. However, the maximum evaluation period covered by these studies was two years after surgery, hence the need to undertake further studies of longer duration in order to achieve a more thorough understanding of this association.

Skeletal and hormonal effects of magnesium deficiency

Magnesium (Mg) is the second most abundant intracellular cation where it plays an important role in enzyme function and trans-membrane ion transport. Mg deficiency has been associated with a number of clinical disorders including osteoporosis. Osteoporosis is common problem accounting for 2 million fractures per year in the United States at a cost of over $17 billion dollars. The average dietary Mg intake in women is 68% of the RDA, indicating that a large proportion of our population has substantial dietary Mg deficits. The objective of this paper is to review the evidence for Mg deficiency-induced osteoporosis and potential reasons why this occurs, including a cumulative review of work in our laboratories and well as a review of other published studies linking Mg deficiency to osteoporosis. Epidemiological studies have linked dietary Mg deficiency to osteoporosis. As diets deficient in Mg are also deficient in other nutrients that may affect bone, studies have been carried out with select dietary Mg depletion in animal models. Severe Mg deficiency in the rat (Mg at <0.0002% of total diet; normal = 0.05%) causes impaired bone growth, osteopenia and skeletal fragility. This degree of Mg deficiency probably does not commonly exist in the human population. We have therefore induced dietary Mg deprivation in the rat at 10%, 25% and 50% of recommended nutrient requirement. We observed bone loss, decrease in osteoblasts, and an increase in osteoclasts by histomorphometry. Such reduced Mg intake levels are present in our population. We also investigated potential mechanisms for bone loss in Mg deficiency. Studies in humans and and our rat model demonstrated low serum parathyroid hormone (PTH) and 1,25(OH)(2)-vitamin D levels, which may contribute to reduced bone formation. It is known that cytokines can increase osteoclastic bone resorption. Mg deficiency in the rat and/or mouse results in increased skeletal substance P, which in turn stimulates production of cytokines. With the use of immunohistocytochemistry, we found that Mg deficiency resulted in an increase in substance P, TNFalpha and IL1beta. Additional studies assessing the relative presence of receptor activator of nuclear factor kB ligand (RANKL) and its decoy receptor, osteoprotegerin (OPG), found a decrease in OPG and an increase in RANKL favoring an increase in bone resorption. These data support the notion at dietary Mg intake at levels not uncommon in humans may perturb bone and mineral metabolism and be a risk factor for osteoporosis.

Determinants of 25-hydroxyvitamin D levels in African-American and Caucasian male veterans

SUMMARY

Among 307 males seen in VA Medical Center, independent determinants (p < 0.01 for all) of serum 25-hydroxyvitamin D [25(OH)D] levels included race, vitamin D supplements, BMI, dietary calcium intake and smoking, but not age. Negative association between 25(OH)D and parathyroid hormone (PTH) was similar for Caucasian and African-American men.

INTRODUCTION

In this prospective cohort study, we examined determinants of serum 25-hydroxyvitamin D [25(OH)D] levels and the relationship between 25(OH)D and PTH levels and body mass index (BMI).

METHODS

Male veterans (n = 307) were recruited at a VA Medical Center. Serum levels of PTH and 25(OH)D were obtained. Surveys and chart reviews were completed. Vitamin D insufficiency was defined as 25(OH)D <30 ng/ml. Univariate and multivariate regression analyses were performed.

RESULTS

Among 232 African-American (AA) men (mean +/- SD), 25(OH)D level (21.4 +/- 10.4 ng/ml) was lower and prevalence of insufficiency (80%) was higher than among 75 Caucasians (C; 28.5 +/- 11.1 ng/ml and 53%, respectively, p < 0.01 for both). In multivariate regression analysis, independent determinants (p < 0.01 for all) of 25(OH)D levels included AA race, vitamin D supplements, BMI, dietary calcium intake, and smoking. Despite lower 25(OH)D levels in African-Americans, PTH levels were similar to those seen in Caucasians. There was a significant (p < 0.02) negative linear association between 25(OH)D and PTH in African-American (r(2) = 0.05) and Caucasian (r(2) = 0.08) men, and there was no difference between the slopes of the relationship.

CONCLUSIONS

25(OH)D levels are determined by modifiable risk factors such as vitamin D supplementation in both AA and C males. The negative association between 25(OH)D and PTH is similar between the two races.

Elevated serum PTH is independently associated with poor outcomes in older patients with hip fracture and vitamin D inadequacy

To determine whether serum 25(OH)D and/or PTH levels in older patients with hip fracture (HF) could predict short-term clinical outcomes, we conducted a prospective observational study of 287 consecutive HF patients (mean age 81.9 + or - 7.5 [SD] years, 72% females). The prevalence of vitamin D inadequacy (25[OH]D < 80 nmol/l) was 97.1%, that of vitamin D deficiency (25[OH]D < 50 nmol/l) was 79.8%, and that of elevated PTH level (>6.8 pmol/l) was 35.5%. After adjustment for age and sex, PTH was significantly associated with in-hospital mortality (OR = 1.12, 95% CI 10.5-1.20, P < 0.001), myocardial injury (OR = 1.05, 95% CI 1.03-1.15, P = 0.002), prolonged length of stay (LOS > or = 20 days; OR = 1.05, 95% CI 1.01-1.06, P = 0.044), and being discharged to institutional care (OR = 1.07, 95% CI 1.01-1.18, P = 0.48). Secondary hyperparathyroidism (SHPT), but not vitamin D deficiency, was associated with older age, a higher prevalence of trochanteric fracture, coronary artery disease, hypertension, previous stroke, renal impairment, increased levels of serum osteocalcin, bone-specific alkaline phosphatase, and adiponectin as well as a significantly higher in-hospital mortality (11.8 vs. 0.54%, P = 0.001), perioperative myocardial injury (32.7 vs. 22.5%, P = 0.043), LOS > or = 20 days (40.2 vs. 26.9%, P = 0.017), and being discharged to institutional care (29.5 vs. 14.6%, P = 0.019). In multivariate regression analyses, SHPT was strongly associated with in-hospital mortality and LOS > or = 20 days. We conclude that elevated PTH (but not vitamin D deficiency per se) is a strong independent predictor of poor outcomes in older patients.

Relation of body fat indexes to vitamin D status and deficiency among obese adolescents

BACKGROUND

Data on the relation between vitamin D status and body fat indexes in adolescence are lacking.

OBJECTIVE

The objective was to identify factors associated with vitamin D status and deficiency in obese adolescents to further evaluate the relation of body fat indexes to vitamin D status and deficiency.

DESIGN

Data from 58 obese adolescents were obtained. Visceral adipose tissue (VAT) was measured by computed tomography. Dual-energy X-ray absorptiometry was used to measure total bone mineral content, bone mineral density, body fat mass (FM), and lean mass. Relative measures of body fat were calculated. Blood tests included measurements of 25-hydroxyvitamin D [25(OH)D], parathyroid hormone (PTH), osteocalcin, type I collagen C-telopeptide, hormones, and metabolic factors. Vitamin D deficiency was defined as 25(OH)D < 20 ng/mL. PTH elevation was defined as PTH > 65 ng/mL.

RESULTS

The mean (+/-SD) age of the adolescents was 14.9 +/- 1.4 y; 38 (66%) were female, and 8 (14%) were black. The mean (+/-SD) body mass index (in kg/m(2)) was 36 +/- 5, FM was 40.0 +/- 5.5%, and VAT was 12.4 +/- 4.3%. Seventeen of the adolescents were vitamin D deficient, but none had elevated PTH concentrations. Bone mineral content and bone mineral density were within 2 SDs of national standards. In a multivariate analysis, 25(OH)D decreased by 0.46 +/- 0.22 ng/mL per 1% increment in FM (beta +/- SE, P = 0.05), whereas PTH decreased by 0.78 +/- 0.29 pg/mL per 1% increment in VAT (P = 0.01).

CONCLUSIONS

To the best of our knowledge, our results show for the first time that obese adolescents with 25(OH)D deficiency, but without elevated PTH concentrations, have a bone mass within the range of national standards (+/-2 SD). The findings provide initial evidence that the distribution of fat may be associated with vitamin D status, but this relation may be dependent on metabolic factors. This study was registered at www.clinicaltrials.gov as NCT00209482, NCT00120146.

Relationships of serum 25-hydroxyvitamin D to bone mineral density and serum parathyroid hormone and markers of bone turnover in older persons

CONTEXT

Serum 25-hydroxyvitamin D [25(OH)D] may influence serum PTH and other parameters of bone health up to a threshold concentration, which may be between 25 and 80 nmol/liter.

OBJECTIVE

The aim of the study was to assess the threshold serum 25(OH)D with regard to PTH, bone turnover markers, and bone mineral density (BMD).

DESIGN AND SETTING

This was part of the Longitudinal Aging Study Amsterdam, an ongoing cohort study.

PARTICIPANTS

A total of 1319 subjects (643 men and 676 women) between the ages of 65 and 88 yr participated in the study.

MAIN OUTCOME MEASURES

Serum 25(OH)D, PTH, osteocalcin, urinary deoxypyridinoline/creatinine, quantitative ultrasound of the heel, BMD of lumbar spine and hip, total body bone mineral content, and physical performance. The relationship between the variables was explored by analysis of covariance and the locally weighted regression (LOESS) plots.

RESULTS

Serum 25(OH)D was below 25 nmol/liter in 11.5%, below 50 nmol/liter in 48.4%, below 75 nmol/liter in 82.4%, and above 75 nmol/liter in 17.6% of the respondents. Mean serum PTH decreased gradually from 5.1 pmol/liter when serum 25(OH)D was below 25 nmol/liter to 3.1 pmol/liter when serum 25(OH)D was above 75 nmol/liter (P < 0.001) without reaching a plateau. All BMD values were higher in the higher serum 25(OH)D groups, although only significantly for total hip (P = 0.01), trochanter (P = 0.001), and total body bone mineral content (P = 0.005). A threshold of about 40 nmol/liter existed for osteocalcin and deoxypyridinoline/creatinine, 50 nmol/liter for BMD, and 60 nmol/liter for physical performance.

CONCLUSIONS

Low serum 25(OH)D concentrations are common in the elderly. Bone health and physical performance in older persons are likely to improve when serum 25(OH)D is raised above 50-60 nmol/liter.

Factors associated with elevated or blunted PTH response in vitamin D insufficient adults

OBJECTIVES

The purpose of this study was to examine factors associated with high or low parathyroid hormone (PTH) levels in relationship to vitamin D insufficiency.

DESIGN

This was a cross-sectional study consisting of 516 healthy men and women, aged 30-85, all Caucasians with vitamin D insufficiency [serum 25(OH)D<45 nmol L(-1)]. The group was divided into quartiles by PTH levels and the highest and lowest quartiles were compared with regard to various factors likely to affect calcium metabolism. We used stepwise multivariable logistic regression to determine the independent association between PTH levels and other variables for men and women separately.

RESULTS

We found that men in the lowest PTH quartile were significantly younger, had less energy intake, lower body mass index (BMI) and better kidney function compared with the highest PTH quartile. They had also higher ionized calcium, insulin-like growth factor (IGF1) and testosterone and were more likely to smoke. Women within the lowest PTH quartile were younger, had lower BMI and magnesium values and higher IGF1 levels and were more likely to smoke. Stepwise multivariate regression showed that IGF1, testosterone and BMI were significantly associated with PTH in men (R(2)=0.472) but smoking, BMI and kidney function in women (R(2)=0.362).

CONCLUSIONS

Our results indicate that during vitamin D insufficiency, factors other than calcium and vitamin D may modify PTH response. These factors may be different between sexes and we have identified novel factors, IGF1 and testosterone in men which may be compensatory in nature and confirmed previous factors such as smoking, BMI and kidney function in women.

Vitamin D: current status and perspectives

The role of vitamin D in maintaining bone health has been known for decades. Recently, however, the discovery that many tissues expressed the vitamin D receptor and were able to transform the 25-OH vitamin D into its most active metabolite, 1,25-(OH)

Clin Chem Lab Med 2009;47:120–7.

Hypovitaminosis D and secondary hyperparathyroidism in resident physicians of a general hospital in southern Brazil

OBJECTIVES

To evaluate the prevalence of hypovitaminosis D and secondary hyperparathyroidism in resident physicians of a general hospital in southern Brazil and identify associated factors.

DESIGN

Cross-sectional study.

POPULATION

Resident physicians of Hospital de Clinicas de Porto Alegre, Porto Alegre, southern Brazil.

PARTICIPANTS

Seventythree subjects age 26.4+/-1.9.

MEASUREMENTS

Serum PTH, 25- hydroxyvitamin D [25(OH)D], total calcium, phosphorus, magnesium, creatinine, and alkaline phosphatase were measured. In addition calcium, creatinine, and magnesium were measured in urine. Fractional excretion of calcium and magnesium were calculated. Calcium intake was estimated by a food intake questionnaire.

RESULTS

Mean serum levels of 25(OH)D were 17.9+/-8.0 ng/ml and 57.4% presented 25(OH)D below 20 ng/ml. Secondary hyperparathyroidism, defined as serum PTH > or =48 pg/ml and normal or low serum calcium, was identified in 39.7% of the individuals. Mean serum levels of magnesium were higher (p=0.02) and the fractional excretion of calcium was lower (p<0.001) in individuals with secondary hyperparathyroidism. Serum PTH levels were positively correlated with body mass index (r=0.33 and p=0.006) and serum magnesium levels (r=0.33 and p=0.02) and negatively correlated with serum 25(OH)D levels (r=-0.33 and p=0.008), estimated calcium intake (r=-0.25 and p=0.04), and fractional excretion of calcium (r=-0.34 and p=0.009).

CONCLUSION

Vitamin D deficiency and secondary hyperparathyroidism was very common in resident physicians. Therefore, measures to prevent this situation should be recommended.

Urban tropospheric ozone increases the prevalence of vitamin D deficiency among Belgian postmenopausal women with outdoor activities during summer

CONTEXT

By absorbing sunlight UVB and thereby reducing cutaneous vitamin D photosynthesis, ozone, a common urban pollutant, could cause hypovitaminosis D.

OBJECTIVES

The objective of the study was to establish the characteristics and percentage of subjects with serum 25-hydroxyvitamin D [25(OH)D] less than 75 nmol/liter among postmenopausal women engaging in outdoor activities in either Brussels or the countryside.

DESIGN/SETTING

This was a cross-sectional study conducted in a university research hospital.

PATIENTS/METHODS

Among 249 women consulting for either shoulder tendonitis or lumbar spine osteoarthritis, 121 free of conditions and drugs affecting bone and calcium metabolism completed two food-frequency questionnaires within 15 d and we selected the 85 subjects with retest scores within the +/- 15% of test scores. Other parameters included sun exposure index (SEI), PTH levels, and femoral neck T-score.

RESULTS

Urban residents (n = 38) and rural residents (n = 47) did not differ in mean ages, body mass indices, and vitamin D intakes. When compared with rural inhabitants, urban inhabitants were exposed to ozone levels 3 times higher, and despite a higher mean SEI (113 vs. 87; P < 0.001), they had a higher prevalence of 25(OH)D less than 75 nmol/liter (84 vs. 38%). After adjusting for SEI, 25(OH)D was 2-fold higher in rural residents, and after adjusting for 25(OH)D, SEI was 3-fold higher in urban residents. Femoral neck T-scores correlated positively with 25(OH)D and negatively with PTH levels.

CONCLUSIONS

Air pollution may be a neglected risk factor for hypovitaminosis D, which is known to compromise several health outcomes. As long as 25(OH)D is greater than 75 nmol/liter, calcium intakes greater than 17.5 mmol/d are unnecessary to prevent elevations in PTH levels.

Parathyroid response to vitamin D insufficiency: relations to bone, body composition and to lifestyle characteristics

BACKGROUND

Vitamin D insufficiency is very common and is known to cause secondary hyperparathyroidism (SHPT). However, in some subjects the PTH response to low vitamin D levels is blunted, which has been termed functional hypoparathyroidism (FHPT).

AIM

We compared indices of calcium homeostasis, bone metabolism and body composition in subjects with differential PTH responses to low vitamin D levels.

DESIGN

Cross-sectional study. In 405 recent postmenopausal women with vitamin D insufficiency, we compared levels of bone turnover markers, bone mineral density (BMD), body composition, and body weight between subjects with SHPT and FHPT.

RESULTS

Plasma 25-hydroxyvitamin D (P-25OHD) levels were slightly higher (P < 0.05) in SHPT compared with FHPT. SHPT was associated with higher levels of osteocalcin and bone-specific alkaline phosphatase, whereas whole body BMD and hip- and lumbar spine-BMD were significantly reduced. Subjects with SHPT had a 7% (P < 0.01) higher body weight and a 23% higher fat mass (P < 0.01) than subjects with FHPT, whereas lean tissue mass did not differ between groups. In SHPT, fat mass was increased by 14% (P < 0.001) at the upper and lower extremities and by 33% (P < 0.001) at the trunk. In a regression model, significant predictors of fat mass was P-PTH (r(p) = 0.248, P < 0.01) and P-osteocalcin (r(p) = -0.115, P = 0.02), with no effects of P-25OHD or P-creatinine levels.

CONCLUSIONS

Effects of vitamin D insufficiency on bone is associated with the PTH responses. The increased body weight and fat mass in SHPT compared with FHPT may imply that PTH excess contributes to fat accumulation.

Sickle cell bone disease: response to vitamin D and calcium

Bone disease with osteoporosis and osteomalacia are common in sickle cell disease (SCD). Some patients have vitamin D deficiency and low bone mineral density (BMD). The role of vitamin D and calcium supplementation to restore bone health in SCD has not been well studied. In 14 adults with SCD, we measured 25(OH)D (25-hydroxyvitamin D) and BMD at the femoral neck, lumbar spine, and distal third of the ulna plus radius, along with markers of bone resorption (CTx; C-terminal component of pro-collagen type I) and bone formation (osteocalcin) before and after 12 months of vitamin D(2) and calcium carbonate treatment. Pretreatment, all patients were vitamin D deficient with a mean 25(OH)D level of 11.6 [corrected] +/- 4 [corrected] ng/ml, had low BMD at the lumbar spine (L-spine), 0.87 +/- 0.11 g/cm(2) (mean Z-score of -2.6 3 +/- 0.71 SD and T score of -2.31 +/- 0.75 SD), femoral neck, 0.8 +/- 0.18 g/cm(2) (mean Z-score -1.36 +/- 0.84, T-score -1.14 +/- 0.75), and the distal radius and ulna, 0.6 +/- 0.17 g/cm(2) (mean Z-score -1.18 +/- 0.79, T-score -1.01 +/- 0.74) and had elevated CTx (0.87 +/- 0.5 ng/ml) and osteocalcin levels (12.3 +/- 3.7 ng/mul). After treatment, all patients corrected their 25(OH)D level (34.6 [corrected] +/- 11 [corrected] ng/ml) (P < 0.001) with a 3.6% +/- 3.9% increase in BMD at the L-spine (P = 0.009), 4.6% +/- 8.5% increase at the femoral neck (P = 0.05) and 6.5% +/- 12.6% increase at the distal radius plus ulna (P = 0.09). CTx, osteocalcin, and PTH(i) levels were unchanged. Treatment of adult SCD with vitamin D and calcium can restore 25(OH)D levels to normal and improve BMD, but, markers of bone resorption remained unchanged. Screening for vitamin D deficiency and BMD in SCD patients seems warranted.

Low prevalence of vitamin D deficiency among adolescents with anorexia nervosa

Fifty adolescents with AN and 200 healthy girls underwent vitamin D screening. Girls with AN reported exceptional compliance with vitamin D supplementation and PTH concentrations were lower. Vitamin D deficiency was less common in the group with AN, but when race was considered, the trend was no longer significant.

INTRODUCTION

The objective of this study was to determine whether patients with anorexia nervosa (AN) are more compliant with supplementation and have a lower prevalence of vitamin D deficiency than healthy controls.

METHODS

Fifty adolescents with AN and 200 controls were compared using anthropometric and lifestyle data, serum 25-hydroxyvitamin D (25OHD) and parathyroid hormone (PTH) concentrations, and prevalence of vitamin D deficiency.

RESULTS

The prevalence of deficiency (<20 ng/mL) was 2% in the AN group vs. 24% among controls (p = 0.003). 25OHD was similar among white participants with AN and white controls (39.5 vs. 36.0 ng/mL, p = 0.20), but higher than in non-white controls (20.6 ng/mL). Significantly more girls with AN reported vitamin D supplementation (86%) than the full control (14%) or white subgroup (27%) (p < 0.001). Participants with AN had lower PTH concentrations than controls, (27.8 vs. 47.4 pg/mL, p = 0.009), a trend that lost significance after age and race adjustment (41.7 pg/mL, p = 0.12).

CONCLUSIONS

Compared to healthy controls, adolescents with AN had a lower prevalence of vitamin D deficiency and PTH concentration. However, 25OHD and PTH concentrations were similar after adjustment for race and age. The trend of lower PTH levels in adolescents with AN, accompanied by exceptional compliance with supplementation, may have bone health implications for these patients.

Relationship between serum parathyroid hormone, vitamin D sufficiency, age, and calcium intake

Vitamin D deficiency is extremely common among elderly subjects and it has been associated with poor bone health, and to a number of other conditions. The ideal 25-hydroxy-vitamin D [25(OH)D] concentration, reflecting the size of vitamin D deposits, are generally retained those not associated with any marginal increase in serum parathyroid hormone (PTH). These threshold values vary considerably and this may be due to the interaction of other factors. The aim of the study is to assess whether age and calcium intake interact with the relationship between 25(OH)D and PTH. Data from a survey on the prevalence of hypovitaminosis D in elderly women in Italy were analysed in order to verify whether age and calcium intake were interfering on the 25(OH)D/PTH relationship. A total of 697 women were available for analysis. Serum PTH levels were significantly correlated with age, 25(OH)D and calcium intake (p<0.001) and in a multivariate model they all significantly contributed to explain PTH variance (R(2)=24.4%). In 39 elderly osteoporotic women on a low calcium intake and given vitamin D supplements (2000-3000 IU daily for >8 months) able to increase 25(OH)D levels above 110 nMol/l, PTH levels were maintained below 35 pg/mL. The minimum 25(OH)D levels to be recommended depends largely on the age and the calcium intake. In elderly individuals not taking calcium supplements in order to keep serum PTH levels strictly within the normal range 25(OH)D serum levels should be maintained above ca. 120 nMol/L.

Hypovitaminosis D and parathyroid hormone response in the elderly: effects on bone turnover and mortality

OBJECTIVE

To investigate whether absence of secondary hyperparathyroidism in the presence of hypovitaminosis D has altered bone turnover, fracture risk and mortality.

DESIGN

A prospective cohort study.

PATIENTS

A total of 1280 older men and women living in residential care facilities.

MEASUREMENTS

We measured baseline serum 25-hydroxyvitamin D (25OHD), serum intact PTH, serum amino-terminal propeptide of type I collagen (PINP) and serum carboxy-terminal telopeptide of type I collagen (CTX-I). Deaths and fractures were recorded prospectively.

RESULTS

Hypovitaminosis D (25OHD < 39 nmol/l) and absence of secondary hyperparathyroidism (PTH > 7.0 pmol/l) in the presence of hypovitaminosis D were common in this sample with a prevalence of 77.5% and 53.3%, respectively. In the presence of hypovitaminosis D, residents showing a hyperparathyroid response (n = 406) had significantly higher serum bone turnover markers than individuals with serum PTH levels < or = 7.0 pmol/l (termed 'low vitamin D, normal PTH', n = 463). After adjusting for risk factors, mortality was significantly higher in the secondary hyperparathyroidism group than in the 'low vitamin D, normal PTH' group [hazard ratio (HR) = 1.35, 95% confidence interval (CI) 1.12-1.64; P = 0.002]. All residents with serum PTH levels < or = 7.0 pmol/l (n = 603) were similar with regard to both bone turnover and mortality, independent of their actual vitamin D status.

CONCLUSION

Absence of secondary hyperparathyroidism in the presence of hypovitaminosis D appears to be common in the frail elderly and is associated with longer survival, similar to that observed in vitamin D-replete elderly subjects.

High prevalence of hypovitaminosis D and secondary hyperparathyroidism in elders living in nonprofit homes in South Brazil

OBJECTIVES

Hypovitaminosis D (HD) and secondary hyperparathyroidism (SHP) are common in elders, and many factors could contribute to them. The objectives of this study were to estimate the prevalence of HD, SHP, and its associated factors, in individuals living in nonprofit homes for elders in south Brazil. Design Cross-sectional study.

METHODS

Serum 25-hydroxyvitamin D 25(OH)D, intact parathyroid hormone (PTH), total calcium, phosphorus, alkaline phosphatase, magnesium, creatinine, and albumin levels were measured in late spring, November, 2005. The presence of factors potentially related with HD and SHP-age, sex, weight, height, skin phototype, sun exposure, exercise, smoking, use of < or = 5 medications or diuretics or alcohol, and daily calcium ingestion.

RESULTS

102 subjects age 77.8 +/- 9.0 were included in the study. HD was found in 85.7% and SHP in 53% of the subjects. The estimated daily calcium ingestion was 720 mg. There was no association between serum 25(OH)D levels and any of the risk factors evaluated. Serum 25(OH)D levels were correlated with serum PTH (r = -0.358, P = 0.000), calcium (r = 0.306, P = 0.002), and albumin (r = 0.253, P = 0.011) levels. In univariate analysis, SHP was positively associated with age (P = 0.006), and female sex (0.007); and negatively associated with sunlight exposure (P = 0.020), GFR (P = 0.000), Ln25(OH)D (P = 0.002), and total serum calcium (P = 0.024). After multivariate model adjustment, age [OR 1.09 (CI 1.01-1.18); P = 0.024], Ln25(OH)D [OR 0.92 (CI 0.08-0.74); P = 0.013], GFR [OR 0.96 (CI 0.92-0.99); P = 0.013], and hydrochlorothiazide treatment [OR 7.63 (CI 1.67-34.9); P = 0.008] were independently associated with SHP.

CONCLUSIONS

HD and SHP are highly prevalent in elders living in old-age homes. No associations were established between common risk factors and low serum levels of 25(OH)D levels; however, SHP was independently related with age, 25(OH)D, GFR, and hydrochlorothiazide use.

Prevalence of vitamin D depletion among subjects seeking advice on osteoporosis: a five-year cross-sectional study with public health implications

We assessed vitamin D nutritional status in unselected consecutive patients seeking advice on osteoporosis. The prevalence of vitamin D depletion ranged from 15-72% depending upon the cut-off levels used for serum 25-hydroxyvitamin D, and the prevalence did not change over the 5 years of the study.

INTRODUCTION

Vitamin D depletion is a significant public health problem and has been studied in different populations using different cut-off levels, but the optimal level is yet to be established.

METHODS

In a cross-sectional study of 2,924 patients seen for osteoporosis advice we determined the prevalence of vitamin D depletion, as assessed by 25-hydroxyvitamin D (25-OHD), using three different cut-off levels stratified by gender, race and the year of the study over 5 years.

RESULTS

Mean age was 68.3 +/- 10.0 years; 90% women and 88% white. Mean 25-OHD level was 24.6 +/- 10 ng/ml and mean PTH was 48.4 +/- 32 pg/ml. The prevalence of vitamin D depletion was 15% with a cut-off level of <15 ng/ml, and rose to 32% and 72% with cut-off levels <20 ng/ml and <30 ng/ml, respectively. The prevalence was higher in men and blacks and remained constant over 5 years, regardless of the cut-off level. The expected inverse relationship between 25-OHD and PTH was observed irrespective of gender or ethnicity.

CONCLUSIONS

The prevalence of vitamin D depletion in patients seeking advice for osteoporosis is high and did not change over the 5 years of the study.

Vitamin D status and response to Vitamin D(3) in obese vs. non-obese African American children

BACKGROUND

Serum 25-hydroxyvitamin D (25(OH)D) is low in obese adults.

OBJECTIVE

To examine serum 25(OH)D in obese (BMI >95th percentile for age) vs. non-obese (BMI = 5th-75th percentile for age) 6-10-year-old African American children and compare their differences in therapeutic response to vitamin D supplementation.

METHODS AND PROCEDURES

In an open label non-randomized pre-post comparison 21 obese (OB) and 20 non-obese (non-OB) subjects matched for age, sex, skin color, and pubertal maturation were treated with 400 IU of vitamin D(3) daily for 1 month. Serum 25(OH)D, 1,25-dihydroxyvitamin D (1,25(OH)(2)D), parathyroid hormone (PTH), leptin, and markers of bone turnover (serum bone-specific alkaline phosphatase (BSAP), osteocalcin (OC), and urine n -telopeptide cross-links of type 1 collagen (urine NTX)) were measured. Vitamin D deficiency was defined as serum 25(OH)D < or =20 ng/ml and insufficiency as 21-29 ng/ml respectively.

RESULTS

Vitamin D deficiency occurred in 12/21 (57%) OB vs. 8/20 (40%) non-OB at baseline (P = 0.35) and persisted in 5/21 (24%) OB vs. 2/18 (11%) non-OB (P = 0.42) after treatment. When the cohort was stratified by the baseline levels of 25(OH)D, there were differences in the response to treatment in the obese and non-obese cohorts.

DISCUSSION

Vitamin D deficiency was common among OB and non-OB preadolescent African American children, and 400 IU of vitamin D(3) (2x the recommended adequate intake) daily for 1 month was inadequate to raise their blood levels of 25(OH)D to > or =30 ng/ml.

Vitamin D endocrine physiology

Quantitative aspects of vitamin D(3) endocrine physiology are briefly reviewed, together with the supporting evidence. Net calcium absorption of at least 200 mg/d is required to offset typical obligatory losses and thereby to protect the skeleton. The ability of the body to regulate intestinal calcium absorption is optimal at serum 25-hydroxyvitamin D(3) concentrations >80 nM. Vitamin D(3) inputs from all sources required to sustain such a level amount to 3600-4200 IU/d. Daily oral intakes as high as 10,000 IU are safe.

Vitamin D therapy in clinical practice. One dose does not fit all

INTRODUCTION

Vitamin D is given to most patients with osteoporosis particularly the elderly and those on bisphosphonates. The most widely advocated dose is 800 IU with or without calcium. Whether or not this enables all or most patients to become vitamin D replete in clinical practice is not established.

AIMS

This study investigated a large cohort of patients with osteoporosis attending a metabolic bone clinic to identify if those on vitamin D supplements were adequately treated and if those commenced on treatment developed normal vitamin D levels.

METHODS

Twenty-five hydroxy vitamin D measurements from new all patients attending a district general hospital metabolic bone clinic as part of their preclinic investigations was examined. It was noted as to whether or not they were taking calcium and or vitamin D supplements. Patients not on supplements but with a low baseline vitamin D were treated with supplements and then had a repeat measurement after at least 3 months to assess whether or not they were replete.

RESULTS

From the database of 1028 patients, 100 had preclinic and follow-up vitamin D levels. They were of average age 61 years (SD 12) with a mean baseline vitamin D of 26 nmol/l. The mean posttreatment level was 58 nmol/l (SD 25). Posttreatment vitamin D levels were < 60 nmol/l in 55%, < 50 nmol/l in 36%, < 40 nmol/l in 24% and < 30 nmol/l in 13% and < 20 nmol/l in 4%. In 41 patients on Calcichew D3 Forte two tablets per day pretreatment vitamin D was 24 nmol/l (SD 16) and posttreatment 62 nmol/l (SD 28). Of this subgroup posttreatment 41% were < 60 nmol/l, 27% < 50 nmol/l, 22% < 40 nmol/l and 10% < 30 nmol/l. Two hundred and ten patients on vitamin D treatment preclinic had a mean vitamin D level of 64 nmol/l (SD 28). One hundred and twenty-four patients already on two tablets of Calcichew D3 Forte per day had a mean of 68 nmol/l (SD 28) of whom 38% were < 60 nmol/l, 24% < 50 nmol/l, 16% < 40 nmol/l, 6% < 30 nmol/l and 3% < 20 nmol/l.

CONCLUSION

Vitamin D therapy with conventional treatment improves serum levels of 25 hydroxy vitamin D but still leaves some patients with significant insufficiency and therefore the same dose of vitamin D is not appropriate for all.

Assessment of endocrine and nutritional status in age-related catabolic states of muscle and bone

PURPOSE OF REVIEW

Bone loss and muscle wasting are associated with increased morbidity and mortality in the elderly, most frequently as a result of fractures associated with poor neuromuscular conditioning leading to accidental falls. This paper reviews data that link pathways of the immune and endocrine systems with bone and muscle pathophysiology, as well as data on the impact of nutrition and physical activity on these systems.

RECENT FINDINGS

The growth hormone-insulin-like growth factor I axis and deficiencies in sex steroid hormones in aging appear linked with changes in the hypothalamic-pituitary-adrenal axis and immune function, accompanied by increased activity of the tumour necrosis factor-alpha axis. This is associated with activation of the RANK/RANKL/osteoprotegerin pathway and insulin resistance, affecting muscle and bone physiology. Vitamin D deficiency contributes to bone loss and muscle wasting, whereas other nutritional defects such as zinc or magnesium deficiencies may further complicate these catabolic states.

SUMMARY

As nutritional deficiencies responsible for bone and muscle derangement are correctable factors, careful nutritional assessment, in addition to evaluation of endocrine and immune status, may provide clinically important information allowing successful management of elderly patients in danger of neuromuscular dysfunction, accidental falls and bone fractures.

Glomerular filtration rate is a major determinant of the relationship between 25-hydroxyvitamin D and parathyroid hormone

The reference range for 25-hydroxyvitamin D (25-OHD) remains uncertain, and it is not clear as to whether interpretation of circulating 25-OHD would be aided by simultaneous measurement of serum parathyroid hormone (PTH). We wanted to define the level of serum 25-OHD associated with a raised serum PTH and to examine the determinants of the relationship between serum 25-OHD and serum PTH concentration. We retrospectively examined data for patients who had a 25-OHD measurement and other biochemical variables over a 12-month period in our center. We found that 28% of patients had a serum 25-OHD level below 50 nmol/L and serum PTH level in the normal reference range, whereas 24% had a serum 25-OHD level below 50 nmol/L with a serum PTH value above the normal reference range. At a serum 25-OHD level of 80 nmol/L, 1.5% had an elevated serum PTH and, at 50 nmol/L, 8% had raised serum PTH. Further examination showed that for patients with low serum 25-OHD, low glomerular filtration rate (GFR) was a major determinant of the PTH response. These data confirm an inverse correlation between serum 25-OHD and serum PTH. Minimal numbers of patients (1.5% of the study group) have a raised serum PTH at a serum 25-OHD level of 80 nmol/L. GFR is a major determinant of the PTH response to decreasing serum levels of 25-OHD.

Vitamin D replacement for cirrhosis-related bone disease

The osteoporotic fracture rate in patients with chronic liver disease is approximately twice that of age-matched, control individuals. About 66% of patients with moderately severe cirrhosis and 96% of patients awaiting liver transplantation have vitamin D deficiency. Studies have shown a strong correlation between vitamin D deficiency and bone density, particularly in the hip. Previous studies of vitamin D therapy in cirrhosis-related bone disease have had major design flaws. Most reports and guidelines on the treatment of hepatic bone disease have concluded that vitamin D deficiency does not have a significant pathogenetic role in the development of osteoporosis in cirrhosis, and that there is no evidence for a therapeutic effect of vitamin D supplementation. Conversely, it is generally recommended that patients with cirrhosis and low bone density should receive calcium and vitamin D supplementation; yet there is a paucity of reliable data on the optimal doses to use, as well as a lack of clearly demonstrated benefit. We believe that clinical trials of vitamin D therapy in these patients with liver disease are warranted. As low-dose oral supplementation often will not normalize vitamin D levels or suppress parathyroid hormone activity in cirrhotic patients, high-dose, parenteral vitamin D might be preferable, but further long-term studies are required to assess the benefits and safety of this approach.