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

The Relationship between Renin-Angiotensin-Aldosterone System (RAAS) Activity, Osteoporosis and Estrogen Deficiency in Type 2 Diabetes

Type 2 diabetes (T2D) is associated with a plethora of comorbidities, including osteoporosis, which occurs due to an imbalance between bone resorption and formation. Numerous mechanisms have been explored to understand this association, including the renin-angiotensin-aldosterone system (RAAS). An upregulated RAAS has been positively correlated with T2D and estrogen deficiency in comorbidities such as osteoporosis in humans and experimental studies. Therefore, research has focused on these associations in order to find ways to improve glucose handling, osteoporosis and the downstream effects of estrogen deficiency. Upregulation of RAAS may alter the bone microenvironment by altering the bone marrow inflammatory status by shifting the osteoprotegerin (OPG)/nuclear factor kappa-Β ligand (RANKL) ratio. The angiotensin-converting-enzyme/angiotensin II/Angiotensin II type 1 receptor (ACE/Ang II/AT1R) has been evidenced to promote osteoclastogenesis and decrease osteoblast formation and differentiation. ACE/Ang II/AT1R inhibits the wingless-related integration site (Wnt)/β-catenin pathway, which is integral in bone formation. While a lot of literature exists on the effects of RAAS and osteoporosis on T2D, the work is yet to be consolidated. Therefore, this review looks at RAAS activity in relation to osteoporosis and T2D. This review also highlights the relationship between RAAS activity, osteoporosis and estrogen deficiency in T2D.

Environmental Factors That Affect Parathyroid Hormone and Calcitonin Levels

Calciotropic hormones, parathyroid hormone (PTH) and calcitonin are involved in the regulation of bone mineral metabolism and maintenance of calcium and phosphate homeostasis in the body. Therefore, an understanding of environmental and genetic factors influencing PTH and calcitonin levels is crucial. Genetic factors are estimated to account for 60% of variations in PTH levels, while the genetic background of interindividual calcitonin variations has not yet been studied. In this review, we analyzed the literature discussing the influence of environmental factors (lifestyle factors and pollutants) on PTH and calcitonin levels. Among lifestyle factors, smoking, body mass index (BMI), diet, alcohol, and exercise were analyzed; among pollutants, heavy metals and chemicals were analyzed. Lifestyle factors that showed the clearest association with PTH levels were smoking, BMI, exercise, and micronutrients taken from the diet (vitamin D and calcium). Smoking, vitamin D, and calcium intake led to a decrease in PTH levels, while higher BMI and exercise led to an increase in PTH levels. In terms of pollutants, exposure to cadmium led to a decrease in PTH levels, while exposure to lead increased PTH levels. Several studies have investigated the effect of chemicals on PTH levels in humans. Compared to PTH studies, a smaller number of studies analyzed the influence of environmental factors on calcitonin levels, which gives great variability in results. Only a few studies have analyzed the influence of pollutants on calcitonin levels in humans. The lifestyle factor with the clearest relationship with calcitonin was smoking (smokers had increased calcitonin levels). Given the importance of PTH and calcitonin in maintaining calcium and phosphate homeostasis and bone mineral metabolism, additional studies on the influence of environmental factors that could affect PTH and calcitonin levels are crucial.

Blunted PTH response to vitamin D insufficiency/deficiency and colorectal neoplasia risk

BACKGROUND & AIMS

In contrast to many observational studies, large-scale randomized trials do not support the protective role of vitamin D for the prevention of colorectal neoplasia. However, in previous studies, individuals with blunted parathyroid hormone (PTH) response to vitamin D insufficiency/deficiency (BPRVID), were not differentiated from those with high PTH response to vitamin D insufficiency/deficiency (HPRVID). Individuals with BPRVID are responsive to magnesium treatment, particularly treatment of magnesium plus vitamin D while those with HPRVID are responsive to vitamin D treatment. We prospectively compared these two distinct groups (i.e. BPRVID and HPRVID) for risk of incident adenoma, metachronous adenoma, and incident colorectal cancer (CRC) METHODS: Three nested case-control studies in the Prostate, Lung, Colorectal and Ovarian Cancer (PLCO) Screening Trial.

RESULTS

We found optimal 25(OH)D levels were associated with a significantly reduced risk of CRC, primarily among women. The associations between 25(OH)D and CRC risk significantly differed by PTH levels, particularly among women. Compared to individuals with optimal levels for both 25(OH)D and PTH, all others were at an elevated risk of incident CRC, primarily in women. We found those with BPRVID had 2.56-fold significantly increased risk of CRC compared to 1.65-fold non-significantly increased risk for those with HPRVID. Among women, we observed those with BPRVID had 4.79-6.25-fold significantly increased risks of incident CRC and adenoma whereas those with HPRVID had 3.65-fold significantly increased risk of CRC.

CONCLUSIONS

Individuals with BPRVID are at higher risks of incident adenoma and CRC compared to those with HPRVID, particularly among women.

Investigation of hypomagnesaemia prevalence and underlying aetiology in a hospitalised cohort of dogs with ionised hypocalcaemia

OBJECTIVES

Calcium is the most abundant mineral in the body and plays a critical role in a wide range of physiological processes. Low concentrations of ionised calcium, the most metabolically available form of calcium, have been linked to an increased risk of adverse clinical outcomes in dogs. Magnesium plays an important role in parathyroid hormone function. The objective of this study was to define the prevalence and aetiology of hypomagnesaemia in a hospitalised cohort of dogs with ionised hypocalcaemia (IHC).

METHODS

A total magnesium reference interval was established using serum biochemistry results from 346 clinically healthy dogs. The clinical records of dogs with IHC were reviewed, and concurrent serum magnesium concentrations were recorded alongside clinical signs and underlying aetiology. The prevalence, clinical presentation and aetiology of hypomagnesaemia were examined in the IHC population.

RESULTS

Two hundred and ninety-five IHC dogs were identified. Hypomagnesaemia was identified in 22%. Total magnesium concentration was significantly higher in dogs with renal disease. The most common cause of concurrent hypomagnesaemia and IHC was gastrointestinal diseases.

CONCLUSION

Low concentrations of serum magnesium occur in approximately one fifth of all dogs with IHC. Further studies are required to clarify the link between magnesium status, IHC and clinical outcome.

Prevalence and Determinants of a Blunted Parathyroid Hormone Response in Young Saudi Women with Vitamin D Deficiency: A Cross-Sectional Study

Vitamin D deficiency is highly prevalent among the Saudi population. Increased parathyroid hormone (PTH) secretion is an appropriate homeostatic response to correct the resultant hypocalcemia. However, not all vitamin D deficiency patients have increased PTH levels. This study determined the prevalence of a blunted PTH response to vitamin D deficiency among apparently healthy young Saudi women and assessed anthropometric and biochemical factors associated with this response by performing a secondary analysis of data obtained from a cross-sectional study conducted at the "Center of Excellence for Osteoporosis research." Overall, 315 women (aged 20-45 years) with vitamin D deficiency (serum 25-hydroxyvitamin D (25(OH)D) levels <30 nmol/L) were included. They were divided into two groups according to the laboratory cutoff value of PTH (<7 or ≥7 pmol/L), and anthropometric and biochemical characteristics of both groups were compared. Women with a blunted PTH response (n = 62, 19.7%) had a significantly lower body mass index (BMI) (P < 0.001) and smaller waist circumference (P=0.001). They also had significantly higher serum 25(OH)D (P=0.001), corrected serum calcium (P < 0.001), and phosphate (P=0.003) levels than those with an elevated PTH response (n = 253, 80.3%). Multiple logistic regression analysis showed that lower BMI (OR = 0.925; 95% CI: 0.949-0.987) and higher 25(OH)D (OR = 1.068; 95% CI: 1.014-1.124) and serum calcium (OR = 8.600; 95% CI: 1.614-45.809) levels were significantly associated with a blunted PTH response (R ² = 0.178). A blunted PTH response to vitamin D deficiency is mainly observed among women with lower BMI. Higher serum calcium and 25(OH)D levels and lower BMI were significant predictors of a blunted PTH response, which may indicate that these subjects are adapting to lower 25(OH)D levels and maintaining normal calcium levels without the need to increase PTH secretion. The mechanisms underlying this adaptation are unclear, and future studies to explore these mechanisms are warranted.

Response of Parathyroid Hormone to Vitamin D Deficiency in Otherwise Healthy Individuals

Background and objectives

Vitamin D deficiency is a global public health issue, which affects people of all ages and ethnicities. However, severe deficiency seems to be more prevalent in the Middle East and South Asia. Evidence suggests that low serum 25-hydroxycholicalciferol [25(OH)D] levels are associated with an increase in parathyroid hormone (PTH). Yet, the 25-OHD levels leading to serum PTH increase are still a matter of debate. The objective of this study is to assess deficiency of vitamin D in otherwise healthy individuals, and to determine the response of the PTH to vitamin D deficiency.

Methods

This observational study was conducted from January 2018 to May 2018. A total of 43 individuals were selected from three separate clinics in Libya (Alrazy clinic, Alhaya clinic, and Alnukbah clinic). Blood drawn from these individuals was assessed for serum calcium, phosphorus, 25(OH)D, and PTH. These data were collected and analyzed using the Statistical Package for Social Sciences (SPSS) version 17.0 for Windows (SPSS Inc., Chicago, IL).

Results

The mean age and standard (SD) of the study participants was 47.4 ± 12.4. The age range was 19-67 years. The ratio of male to female was 1:2. The percentage of individuals with vitamin D deficiency in the study group was 95.3%, whereas the percentage of vitamin D insufficiency was 4.7%. These data suggest that individuals with severe deficiency show higher PTH values (75.66 ng/ml), whereas those with insufficiency showed lower PTH values (37.5 ng/ml).

Conclusion

The population in the present study was overall deficient in 25-OH vitamin D, which indicates a greater need for supplementation with vitamin D. However, not all the individuals with vitamin D deficiency have high levels of PTH, a finding that agrees with the need for new criteria in the management of vitamin D deficiency and the importance of PTH testing.

Association of Vitamin D and Parathyroid Hormone Levels in Overweight and Obese Adolescents

Vitamin D deficiency in known to be high in obese and overweight adolescents. Few studies in other countries have shown lower parathyroid hormone (PTH) levels in obese adolescents despite high vitamin D deficiency. The aim of the study is to assess vitamin D and PTH levels and their relationship in overweight and obese adolescents in Telangana. This cross-sectional study was carried out in 108 overweight and obese boys and girls aged 12-18 years. A pretested Questionnaire was administered to collect information on demographics, sun exposure, medical and nutritional history. Anthropometry and blood sample was collected for estimating 25 hydroxy vitamin D, and PTH. Body mass index Z scores (WHO growth standards) were used for assessing overweight and obesity in adolescents. 54.6% of the subjects were boys. Mean (SD) levels of vitamin D and PTH were 18.25 (9.26) ng/mL and 45.39 (28.23) ng/L respectively. The prevalence of vitamin D deficiency and insufficiency in the current study was 54.6% and 25.9% respectively. However, PTH levels were high only in 24.2% of subjects (> 65 ng/L). There was an inverse but non-significant correlation between vitamin D and PTH. The association was same after adjusting for age, gender and weight. Our study highlights the high prevalence of vitamin D deficiency among overweight and obese adolescents in Telangana. Despite high vitamin D deficiency, very few had high PTH levels and the vitamin D-PTH axis may be altered in overweight and obese adolescents.

Parathyroid hormone response to different vitamin D levels in population-based old and very-old Polish cohorts

BACKGROUND

Low vitamin D (VD) is not always followed by the development of secondary hyperparathyroidism (SHPT). The study aimed to assess the prevalence of SHPT and functional hypoparathyroidism (FHPT) in relation to VD deficiency/insufficiency and factors predisposing to parathyroid hormone (PTH) response in old and very-old Caucasians.

METHODS

A sub-study of the cross-sectional PolSenior project analyzed serum 25(OH)D, intact PTH (iPTH) and C-terminal fibroblast growth factor 23 (cFGF23) concentrations in 3472 (1658 women) individuals aged ≥65 years. SHPT was defined as iPTH concentration > 65 pg/mL, while FHPT as iPTH within the reference range in the presence of 25(OH)D < 30 ng/mL.

RESULTS

SHPT was diagnosed in 426 participants (14%) and was more frequent in very-old (≥ 80 years) than in the old (65-79 years) subgroup (18.8 vs 9.8%; OR = 2.12; 95% CI: 1.72-2.62). While, FHPT was found in 2269 subjects (85.2%) with 25(OH)D < 30 ng/mL, and was more prevalent in the old than very-old subgroup (89.3 vs 80.1%; OR = 2.03; 95% CI: 1.63-2.52). Multiple regression analysis showed that age ≥ 80 years, use of loop diuretics, decreased glomerular filtration rate, higher cFGF23 level but lower calcium and phosphate concentrations, predispose for the occurrence of SHPT.

CONCLUSIONS

The interrelation between 25(OH)D deficiency and PTH response is complex. In older adults, PTH response is related to VD deficiency, age, impaired kidney function, the use of loop diuretics and the levels of calcium, phosphate, and cFGF23.

The SuprMam1 breast cancer susceptibility locus disrupts the vitamin D/ calcium/ parathyroid hormone pathway and alters bone structure in congenic mice

Breast cancer is a complex disease, and approximately 30% of cases are considered to be hereditary or familial, with a large fraction of this being polygenic. However, it is difficult to demonstrate the functional importance of genes of small effect in population studies, and these genes are not always easily targeted for prevention. The SuprMam (suppressor of mammary tumour) breast cancer susceptibility alleles were previously identified as contributors to spontaneous mammary tumour development in Trp53^+/- mice. In this study, we have generated and characterised congenic mice that contain the BALB/c SuprMam1 (susceptibility) locus on a C57BL/6 (resistant) background and discovered a subtle impairment in the vitamin D/ calcium/ parathyroid hormone (PTH) pathway. This was evident as altered gene expression in the mammary glands of key players in this pathway. Further functional analysis of the mice revealed elevated PTH levels, reduced Cyp27b1 expression in kidneys, and reduced trabecular bone volume/ tissue volume percentage. Plasma 25(OH)D and serum calcium were unchanged. This impairment was a result of genetic differences and occurred only in females, but the elevated PTH levels could be overcome with either calcium or vitamin D dietary supplementation. Either low levels of active vitamin D (1,25(OH)₂D) or chronically elevated PTH levels may contribute to increased breast cancer susceptibility. These indicators are not easily measured in human population studies, but either mechanism may be preventable with dietary calcium or vitamin D supplements. Therefore, SuprMam congenic mice could serve as a valuable model for studying the role of gene-hormone-environment interactions of the vitamin D/ calcium/ PTH pathway in cancer and other diseases and for testing preventive interventions.

Parathyroid Gland Response to Vitamin D Deficiency in Type 2 Diabetes Mellitus: An Observational Study

Background

Studies have linked vitamin D deficiency with the risk of type 2 diabetes mellitus (T2DM) and to the development of chronic complication of diabetes. Vitamin D receptors (VDR) have been found in many tissues in the body including the pancreas, a finding that indicates its role in insulin secretion. In addition, many studies have demonstrated the role of vitamin D and its receptor in insulin sensitivity and signal transduction. Vitamin D deficiency is common throughout the world, but not all vitamin D deficiencies are accompanied by a rise in parathyroid hormone (PTH). The present study was conducted to assess vitamin D deficiency in type 2 diabetic patients in comparison to healthy control and to determine parathyroid gland response to vitamin D deficiency in both groups.

Methods

This observational study was performed during a period from January to October 2018. The study included 151 type 2 diabetic patients selected from three diabetes clinics and 43 age and sex-matched healthy subjects. Informed consent and clinical information were obtained from all participants before the study. Results of the laboratory analysis for serum 25-hydroxyvitamin D (25-OHD), PTH, calcium, and phosphorous were recorded. The data was analyzed using the statistical package for the social sciences (SPSS) Statistics 17.

Results

The results showed low vitamin D concentration in both groups; however, there was no significant difference in vitamin D concentration between diabetic patients and the control patients. A high percentage of PTH level was found in severe vitamin D deficient diabetic patients and healthy controls. The higher percentage of diabetic and normal subjects with mild vitamin D deficiency had a normal PTH level. All healthy subjects with vitamin D insufficiency showed normal PTH concentration. About 10% of diabetic patients with severe vitamin D deficiency had a low PTH level.

Conclusion

The population in our study was generally deficient in 25-OHD irrespective of diabetes mellitus, indicating a greater need for vitamin D supplementation. Not all vitamin D deficient patients have high PTH levels, a finding that supports the emergence of new criteria for vitamin D deficiency, diagnosis and treatment, and highlights the importance of testing PTH in this regard.

Vitamin D and Ageing

One hundred years has passed since the discovery of vitamin D as the active component of cod-liver oil which cured the bone disease rickets. Since then our knowledge of vitamin D has expanded tremendously and has included recognition of the importance of UV radiation as a source of the vitamin as well as the discovery of the vitamin as a nutrient, a pro-hormone and a potent steroid hormone with a major role in calcium and bone metabolism. In the last 25 years or so, the discovery of the vitamin D receptor in over 30 different body tissues together with the existence of the alpha-1-hydroxylase enzyme in these tissues provided evidence of a pleiotropic role of vitamin D outside its classical role in the skeleton. These important discoveries have provided the basis for the increasing interest in vitamin D in the context of nutritional requirements for health including the prevention of chronic diseases of ageing. The recent publication of the Dietary Reference Intake report on vitamin D and calcium by the North American Institute of Medicine (IOM) is the most comprehensive report to date on the basis for setting nutritional requirements for vitamin D. This chapter will summarize the nutritional aspects of vitamin D and discuss the changes in vitamin D metabolism and requirements with ageing. It will summarize key evidence on the relationship between vitamin D status and some of the main ageing related health outcomes including bone, muscle and cognitive health as well as survival focusing on the published literature in very-old adults (those >= 85 years of age).

Clinical Trial on the Effects of Vitamin D Supplementation on Metabolic Profiles in Diabetic Hemodialysis

The current study was conducted to assess the effects of vitamin D supplementation on insulin metabolism, lipid fractions, biomarkers of inflammation, and oxidative stress in diabetic hemodialysis (HD) patients. This randomized double-blind placebo-controlled clinical trial was carried out among 60 diabetic HD patients. Subjects were randomly allocated into two groups to intake either oral vitamin D3 supplements at a dosage of 50 000 IU (n=30) or placebo (n=30) every 2 weeks for 12 weeks. After 12 weeks of intervention, subjects who received vitamin D supplements compared with the placebo had significantly decreased serum insulin concentrations (-3.4±3.7 vs. +2.0±4.2 μIU/ml, p<0.001), homeostasis model of assessment-estimated insulin resistance (HOMA-IR) (-1.2±1.8 vs. +0.9±2.3, p<0.001), and improved quantitative insulin sensitivity check index (QUICKI) (+0.02±0.03 vs. -0.01±0.02, p<0.001). In addition, compared with the placebo, vitamin D supplementation led to significant reductions in serum high-sensitivity C-reactive protein (hs-CRP) (-1.4±2.5 vs. +1.4±4.8 mg/l, p=0.007), plasma malondialdehyde (MDA) (-0.1±0.2 vs. +0.1±0.2 μmol/l, p=0.009) and a significant increase in plasma total antioxidant capacity (TAC) concentrations (+33.8±56.7 vs. -2.0±74.5 mmol/l, p=0.04). We did not see any significant effect of vitamin D supplementation on lipid profiles and other biomarkers of inflammation and oxidative stress compared with the placebo. Overall, we found that vitamin D supplementation had beneficial effects on serum insulin, HOMA-IR, QUICKI, serum hs-CRP, plasma MDA, and TAC levels among diabetic HD patients for 12 weeks. CLINICAL REGISTRATION:: http://www.irct.ir: IRCT201611155623N92.

Vitamin D, parathyroid hormone and metabolic syndrome - the PORMETS study

BACKGROUND

Vitamin D (VitD) and parathyroid hormone (PTH) play important roles in calcium metabolism and skeletal homeostasis. Estimates of the VitD status in several European countries show large variations between them. In addition, no national population-based estimate has been published. VitD and PTH may also play important roles in cardiovascular risk, which has been suggested to be associated with metabolic syndrome (MetS) and is very prevalent in Portugal. The goal of our study was to evaluate the prevalence of hypovitaminosis D and its determinants as well as PTH serum level determinants and associations of the 25-hydroxyvitamin D and PTH serum levels with MetS and its individual components in a sample of the Portuguese mainland population.

METHODS

PORMETS is a national cross-sectional study that includes a total sample of 4095 adults. A subsample, including 500 participants, was randomly selected for the present study. A structured questionnaire was administered to collect information on personal medical histories and socio-demographic and behavioral characteristics. Blood pressure and anthropometrics measurements were performed. Fasting venous samples were collected and PTH and 25-hydroxyvitamin D were measured. VitD adequacy was classified according to the Institute of Medicine, and MetS was classified according to the Joint Interim Statement recommendations. Multiple linear regression and unconditional logistic regression models were used to estimate the associations between the levels of PTH and 25-hydroxyvitamin D and with MetS and its individual components.

RESULTS

The prevalence of VitD deficiency was 37.7%, and MetS was present in 191 participants (38.4%). The serum PTH levels showed a positive association (OR: 1.014; 95%CI: 1.002, 1.026) with the waist circumference component of MetS. The serum 25-hydroxyvitamin D levels were negatively associated with MetS (OR: 0.957; 95%CI: 0.922, 0.993) as well as with its blood pressure (OR: 0.949; 95%CI: 0.912, 0.987) and triglycerides (OR: 0.930; 95%CI: 0.892, 0.969) components.

CONCLUSION

This study showed a high national prevalence of hypovitaminosis D. The PTH levels showed a significant positive association with the WC component of MetS, and the VitD levels were negatively associated with the BP and triglycerides components as well as with the MetS.

Association of air particulate pollution with bone loss over time and bone fracture risk: analysis of data from two independent studies

BACKGROUND

Air particulate matter (PM) is a ubiquitous environmental exposure associated with oxidation, inflammation, and age-related chronic disease. Whether PM is associated with loss of bone mineral density (BMD) and risk of bone fractures is undetermined.

METHODS

We conducted two complementary studies of: (i) long-term PM <2.5 μm (PM_2.5) levels and osteoporosis-related fracture hospital admissions among 9.2 million Medicare enrollees of the Northeast/Mid-Atlantic United States between 2003-2010; (ii) long-term black carbon [BC] and PM_2.5 levels, serum calcium homeostasis biomarkers (parathyroid hormone, calcium, and 25-hydroxyvitamin D), and annualized BMD reduction over a 8-year follow-up of 692 middle-aged (46.7±12.3 yrs), low-income BACH/Bone cohort participants.

FINDINGS

In the Medicare analysis, risk of bone fracture admissions at osteoporosis-related sites was greater in areas with higher PM_2.5 levels (Risk ratio [RR] 1.041, 95% Confidence Interval [CI], 1.030, 1.051). This risk was particularly high among low-income communities (RR 1.076; 95% CI, 1.052, 1.100). In the longitudinal BACH/Bone study, baseline BC and PM_2.5 levels were associated with lower serum PTH (Estimate for baseline one interquartile increase in 1-year average BC= -1.16, 95% CI -1.93, -0.38; Estimate for baseline one interquartile increase in 1-year average PM_2.5= -7.39; 95%CI -14.17, -0.61). BC level was associated with higher BMD loss over time at multiple anatomical sites, including femoral neck (-0.08%/year per one interquartile increase; 95% CI -0.14, -0.02%/year) and ultradistal radius (-0.06%/year per one interquartile increase; 95% CI -0.12, -0.01%/year).

INTERPRETATION

Our results suggest that poor air quality is a modifiable risk factor for bone fractures and osteoporosis, especially in low-income communities.

Attenuated PTH responsiveness to vitamin D deficiency among patients with type 2 diabetes and chronic hyperglycemia

BACKGROUND

The short and long-term relationship between hyperglycemia and PTH level among patients suffering from both diabetes type 2 and vitamin D deficiency were evaluated.

METHODS

This was a cross sectional study performed at Dubai Diabetes Center, UAE. To demonstrate the relationship between hyperglycemia and PTH level, subjects with type 2 diabetes and vitamin D deficiency (124 adults) were divided into 4 groups based on their FPG and HbA1c levels.

RESULTS

Mean vitamin D and PTH levels among subjects with HbA1c≤7% (53mmol/mol) were 14.05ng/ml and 19.51pg/ml respectively. On the other hand, mean vitamin D and PTH levels among subjects with HbA1c≥10% (86mmol/mol) were significantly lower at 11.77ng/ml and 17.75pg/ml respectively. The product of vitamin D and PTH among subjects with an HbA1c≤7% (53mmol/mol) was 250.380, compared with only 197.710 among subjects with HbA1c≥10 (86mmol/mol). Regression analysis for subjects older than 50years shows a significant negative effect of HbA1c on the PTH level. Mean calcium level among subjects with HbA1c≤7% (53mmol/mol) was 8.80mg/dl compared with 8.94mg/dl when HbA1c is ≥10% (86mmol/mol) with no statistical difference. Although high FPG was associated with a lower PTH level, such association was not statistically significant.

CONCLUSIONS

Chronic hyperglycemia, as assessed by A1C level, is associated with a significantly attenuated PTH responsiveness to vitamin D deficiency without a significant change in calcium level. On the other hand, there was no significant association between FPG and PTH level.

Severe vitamin D deficiency is common in critically ill patients at a high northern latitude

BACKGROUND

Critically ill patients at southern latitudes have been shown to have low vitamin D levels that were associated with prolonged hospital stay. To our knowledge no studies have been conducted on vitamin D status amongst critically ill patients at high northern latitudes. Despite the Icelandic population traditionally taking vitamin D supplements, we hypothesized that the majority of critically ill patients in Reykjavik, Iceland have low vitamin D levels.

METHODS

This was a prospective observational study on 122 patients admitted to Landspitali University Hospital intensive care unit. Serum vitamin D (25(OH)D) was measured in all patients on two occasions (first and second day). The prevalence of vitamin D deficiency and its effect on hospital stay was calculated.

RESULTS

Only 9% of patients had vitamin D levels recommended for good health (>75 nmol/l) and 69% were deficient (25(OH)D < 50 nmol/l). The average difference between the first and second vitamin D samples was 2.8 nmol/l. Forty-three percentage of the severely vitamin D deficient stayed in the ICU for more than 4 days compared to 19% of patients with better status (P = 0.196).

DISCUSSION

Vitamin D deficiency is very common in critically ill patients at high northern latitudes and patients with severely deficient vitamin D levels had trend towards longer intensive care unit stay. Furthermore, 43% of the patients had vitamin D levels under 25 nmol/l that is associated with osteomalacia. It appears that a single vitamin D measurement gives a reasonable clue about the vitamin D status in critically ill patients.

Vitamin D and bone health outcomes in older age

The aim of this review is to summarise the evidence linking vitamin D to bone health outcomes in older adults. A plethora of scientific evidence globally suggests that large proportions of people have vitamin D deficiency and are not meeting recommended intakes. Older adults are at particular risk of the consequences of vitamin D deficiency owing to a combination of physiological and behavioural factors. Epidemiological studies show that low vitamin D status is associated with a variety of negative skeletal consequences in older adults including osteomalacia, reduced bone mineral density, impaired Ca absorption and secondary hyperparathyroidism. There seems to be inconsistent evidence for a protective role of vitamin D supplementation alone on bone mass. However, it is generally accepted that vitamin D (17·5 μg/d) in combination with Ca (1200 mg/d) reduces bone loss among older white subjects. Evidence for a benefit of vitamin D supplementation alone on reducing fracture risk is varied. According to a recent Agency for Healthcare Research and Quality review in the USA the evidence base shows mixed results for a beneficial effect of vitamin D on decreasing overall fracture risk. Limitations such as poor compliance with treatment, incomplete assessment of vitamin D status and large drop-out rates however, have been highlighted within some studies. In conclusion, it is generally accepted that vitamin D in combination with Ca reduces the risk of non-vertebral fractures particularly those in institutional care. The lack of data on vitamin D and bone health outcomes in certain population groups such as diverse racial groups warrants attention.

Serum 25-hydroxy vitamin D levels in relation to body mass index: a systematic review and meta-analysis

BACKGROUND

Although several cross-sectional studies have investigated serum vitamin D levels in relation to body mass index (BMI), findings are inconsistent.

OBJECTIVE

This systematic review and meta-analysis of published cross-sectional data was conducted to summarize the evidence on the link between serum vitamin D levels and BMI in adults.

METHODS

PubMed, ISI Web of Science, Scopus and Google scholar database were searched to May 2012 for all relevant published papers. We found 34 articles that reported the correlation coefficients between serum 25-hydroxy vitamin D (25(OH)D) levels and BMI in apparently healthy adults (>18 years). The primary analysis was done on these 34 papers that reported 37 correlation coefficients. To find the source of between-study heterogeneity, our secondary analysis was confined to eight studies that had used random sampling method and reported the correlations for the whole population.

RESULTS

Our meta-analysis on 34 relevant papers revealed an overall significant inverse, but weak, association between serum 25(OH)D levels and BMI (Fisher's Z = -0.15, 95% CI: -0.19, -0.11) with a significant heterogeneity between studies. In the subgroup analysis based on gender and study location (East vs. West), the inverse associations were significant in both genders (male: Fisher's Z = -0.11, 95% CI: -0.14, -0.08 and female: -0.14, 95% CI: -0.21, -0.08) and both study locations (East: -0.09, 95% CI: -0.14, -0.04 and West: -0.23, 95% CI: -0.31, -0.17). In the subgroup analysis based on developmental status of countries, the weak inverse association remained significant in developed countries (-0.17, 95% CI: -0.21, -0.14), but not in developing nations (-0.10, 95% CI: -0.20, 0.01). Using meta-regression, we found that latitude (P = 0.91) or longitude (P = 0.2) of cities did not significantly contribute to the computed effect sizes. When we restricted our analysis to eight selected studies that used random sampling method, we reached the same findings. In this analysis, gender and developmental status of countries explained the between-study heterogeneity.

CONCLUSION

There is a significant inverse weak correlation between serum 25(OH)D levels and BMI in adult population, except for women living in developing countries. Further research particularly in developing countries and populations living near the equator is needed.

Influence of vitamin D status on vertebral fractures, bone mineral density, and bone turnover markers in normocalcemic postmenopausal women with high parathyroid hormone levels

OBJECTIVE

The aims of the study were to analyze whether there is an association between serum PTH and the prevalence of vertebral fractures and its possible dependence on vitamin D status, and to assess the influence of serum 25-hydroxyvitamin D (25OHD) in the relationship between PTH and bone mineral density (BMD) or bone turnover markers (BTMs).

DESIGN, PARTICIPANTS, AND SETTING

A total of 820 postmenopausal women were recruited after excluding those with any known condition that could influence serum PTH levels, except for a possible low serum 25OHD. Serum PTH and 25OHD concentrations, as well as vertebral fracture prevalence, BMD, and BTM (CTX and PINP) values were recorded. Serum PTH levels were divided into tertiles, and women were grouped into those in the highest tertile (>58 pg/ml) and those below. Serum 25OHD levels were stratified in 3 categories (<20, 20-30, and >30 ng/ml).

RESULTS

Vertebral fracture prevalence was greater in women with PTH above 58 pg/ml (odds ratio [OR], 1.72; 95% confidence interval [CI], 1.04-2.84). After stratifying by 25OHD, this difference was only significant in women below 20 ng/ml (OR, 2.00; 95% CI, 1.02-3.87), those with 25OHD between 20 and 30 ng/ml showing a trend toward this (OR, 1.99; 95% CI, 0.92-4.36). Differences in BMD or BTM between women above and below 58 pg/ml of PTH were also observed only in those below 20 ng/ml.

CONCLUSION

Elevated PTH levels are associated with increased prevalence of vertebral fractures, low bone mass, or higher BTM only in the presence of hypovitaminosis D. An adequate nutritional status in the vitamin appears to protect the bone from the deleterious effect of a high PTH.

Circulating 25-hydroxyvitamin D levels in relation to blood pressure parameters and hypertension in the Shanghai Women's and Men's Health Studies

Little is known about the association of circulating 25-hydroxyvitamin D (25(OH)D) and blood pressure (BP) parameters, including systolic and diastolic BP, pulse pressure (PP), mean arterial pressure (MAP) and hypertension in non-Western populations that have not yet been exposed to foods fortified with vitamins and seldom use vitamin D supplements. A cross-sectional analysis of plasma 25(OH)D levels in association with BP measures was performed for 1460 participants (1055 women and 405 men, aged 40-74 years) of two large cohort studies in Shanghai. Multivariable linear and logistic regressions were conducted. Overall, the prevalence of vitamin D deficiency was 55·8 % using National Health and Nutrition Examination Survey, USA criteria and 29·9 % using WHO criteria. The median plasma 25(OH)D level in the population was 38·0 nmol/l for men and 33·6 nmol/l for women (P < 0·01) among participants who were not on antihypertensive drugs. Among men, BP parameters (systolic BP, diastolic BP and MAP) were significantly and inversely associated with higher quintiles of 25(OH)D compared with the lowest quintile (P trend < 0·05 for all). Vitamin D non-deficient status (WHO criteria) was inversely associated with hypertension (ORadjusted = 0·29; 95 % CI 0·10, 0·82). An inverse association was also found between hypertension and the highest quintile of 25(OH)D (ORadjusted = 0·16; 95 % CI 0·04, 0·65 for ≥ 50·6 nmol/l; P trend = 0·02). Among women, no significant associations were found for BP parameters and hypertension. The present study shows that vitamin D deficiency is common among adults in urban China. Circulating 25(OH)D levels were inversely related to the levels of individual BP parameters and hypertension among middle-aged and elderly men but not among women. More research is needed to investigate the potential sex differential associations.

Oral cholecalciferol versus ultraviolet radiation B: effect on vitamin D metabolites in patients with chronic pancreatitis and fat malabsorption - a randomized clinical trial

BACKGROUND

Patients with chronic pancreatitis (CP) often develop fat malabsorption and are susceptible to hypovitaminosis D.

AIM

We wanted to evaluate the intestinal uptake of cholecalciferol in patients with CP and fat malabsorption.

METHODS

We did a prospective placebo-controlled study including patients with verified CP and fat malabsorption. They were randomized to 10 weeks of (A) ultraviolet radiation B (UVB) 6 min weekly in a commercial tanning bed, (B) vitamin D supplement 1,520 IU/daily, or (C) placebo. The vitamin D metabolites 25-hydroxyvitamin D (25OHD) and 1,25-dihydroxyvitamin D (calcitriol) were quantified at the start and end of the study.

RESULTS

In total 30 patients were randomized and 27 completed the study. Compliance to tablets and tanning sessions was >80%. The changes in 25OHD levels in group B (32.3 nmol/l; 95% CI 15-50) were significantly greater than changes in group A (p < 0.001) and group C (p < 0.001). Changes in group A (1.1 nmol/l) did not differ from the placebo group (p = 0.9). Changes in calcitriol levels were identical between groups.

CONCLUSIONS

Daily vitamin D supplements increased 25OHD in patients with CP compared to placebo whereas weekly tanning bed sessions did not.

Vitamin D status has a linear association with seasonal infections and lung function in British adults

Higher vitamin D concentrations have been proposed as a protective 'seasonal stimulus' against influenza, and there are suggestions for associations with other aspects of respiratory health. The aim of the present study was to investigate the relationship of current vitamin D status (measured by 25-hydroxyvitamin D, 25(OH)D) with respiratory infections and lung function. We used cross-sectional data from 6789 participants in the nationwide 1958 British birth cohort who had measurements of 25(OH)D, lung function (forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC)) and respiratory infections available from the age of 45 years. In this population, the prevalence of respiratory infections had a strong seasonal pattern in the opposite direction to the pattern for 25(OH)D concentrations. Each 10 nmol/l increase in 25(OH)D was associated with a 7 % lower risk of infection (95 % CI 3, 11 %) after adjustment for adiposity, lifestyle and socio-economic factors. For FEV1 and FVC, each 10 nmol/l increase in 25(OH)D was associated with 8 (95 % CI 3, 13) ml and 13 (95 % CI 7, 20) ml higher volume, respectively, after controlling for covariates. Associations of 25(OH)D with FEV1 and FVC were only slightly attenuated after further adjustment for infection and other respiratory illness. In conclusion, vitamin D status had a linear relationship with respiratory infections and lung function. Randomised controlled trials are warranted to investigate the role of vitamin D supplementation on respiratory health and to establish the underlying mechanisms.

Association of increased parathyroid hormone with neuroendocrine activation and endothelial dysfunction in elderly men with heart failure

High PTH levels have been reported in patients with chronic heart failure (CHF). Similarly, its levels increase with aging and are related to impaired survival in elderly adults. However, its relationship with neuroendocrine activation and endothelial dysfunction in CHF has not been previously studied. Seventy-three CHF males with New York Heart Association (NYHA) classes II and III and 20 control subjects aged ≥ 55 yr were recruited. PTH, 25-hydroxyvitamin D [25(OH)D], N-terminal pro-brain natriuretic peptide (NT-pro-BNP), adiponectin, and osteoprotegerin were measured. Endothelial function (brachial flow mediated dilation), echocardiography, physical performance, and quality of life were assessed, as well. CHF patients had markedly increased serum PTH (77 ± 33 vs 40 ± 11 pg/ml, p<0.0001), NT-pro-BNP [1809 (2742) vs 67 (74) pg/ml, p<0.0001], adiponectin (17 ± 9 vs 10 ± 2 μg/ml, p<0.0001), osteoprotegerin, whereas 25(OH)D levels were decreased compared to controls. Increased PTH is positively correlated with NTpro- BNP (r=0.399, p<0.0001), adiponectin (r=0.398, p<0.0001), and osteoprotegerin, whereas negatively with 25(OH)D in CHF patients. Additionally, increased serum PTH was associated with endothelial dysfunction, echocardiographic variables of heart failure progression, impaired physical performance, and deteriorated quality of life. In a multivariate linear regression analysis, increased serum PTH was independently associated with neuroendocrine activation (NT-pro-BNP, adiponectin) and endothelial dysfunction in elderly CHF men (R2=0.455). Additionally, demonstrated relations with other well-established variables of heart failure severity suggest the potential role of serum PTH in the pathogenesis and non-invasive monitoring of heart failure progression. Future studies are needed to evaluate the predictive value of serum PTH for clinical outcomes as well as beneficial potential of PTH suppression in CHF patients.

Effects of smoking on severity of disease in primary hyperparathyroidism

In healthy subjects, smoking is associated with lower plasma levels of parathyroid hormone (PTH) and decreased bone mineral density (BMD). The effect of smoking on PTH, skeletal metabolism, and size/histology of the parathyroid glands in primary hyperparathyroidism (PHPT) is unknown. We investigated, in a cross-sectional study, whether smoking affects PTH levels, BMD, and weight/histology of removed parathyroid tissue in PHPT. We studied 344 (285 women) parathyroidectomized patients with PHPT (24% smokers). Biochemistry was determined at the time of diagnosis. BMD was measured before and after surgical cure. Smoking was associated with lower PTH (9.9 ± 1.8 [SD] vs. 12.2 ± 1.8 pmol/l, P < 0.01) and higher phosphate (0.95 ± 0.17 vs. 0.86 ± 0.17 mmol/l, P < 0.01) levels. Adjustments for between-group differences in age, sex, body weight, plasma creatinine, and 25-hydroxyvitamin D (25OHD) levels did not change the findings. Neither weight of removed adenomatous and hyperplastic tissue nor BMD differed according to smoking status. After adjustment for body weight, age, sex, and 25OHD levels, smokers had slightly lower BMD at the whole body but not at the spine, hip, or forearm. Independent of smoking status, surgical cure caused a significant increase in BMD at all measurement sites. In PHPT smoking is associated with lower plasma PTH and higher phosphate levels. Adjustment for confounders of PTH did not change the results. In contrast to healthy subjects, smoking seems not to decrease BMD in PHPT. Smoking may compromise the correct diagnostic evaluation of borderline hyperparathyroidism. It is unknown to what extent smoking in PHPT affects fracture risk and indication for surgery.

Age but not gender modulates the relationship between PTH and vitamin D

CONTEXT

It is unclear whether the relationship between 25-OHD and PTH is modulated by age or gender.

OBJECTIVE

To assess the 25-OHD-PTH relationship in 340 adolescents (10-17 years) and 443 elderly (65-85 years) of the same ethnic group, and living in the same sunny country.

ASSESSMENTS

Calcium intake was estimated. Serum calcium, phosphorus, 25-OHD and PTH were measured. Body fat was determined by DXA.

RESULTS

25-OHD levels were lower in the elderly in the overall group (p<0.001) and within genders. 25-OHD levels were lower in females in the overall group and within age subgroups (p<0.05). PTH levels were higher in the elderly in the overall population and in both genders (p<0.001). There were no gender differences in PTH levels within age subgroups. For the same 25-OHD level, PTH levels were comparable across genders but were 1.5-2 folds higher in the elderly compared to adolescents (p<0.001). PTH correlated positively with age (p<0.001), body fat (p=0.02), and negatively with calcium intake (p<0.001), and 25-OHD (p<0.001). The magnitude of the correlation with 25-OHD decreased after adjustment for age but not for gender. In multivariate analyses, age, 25-OHD and fat mass were independent predictors for PTH. In the elderly, after adjustment for serum creatinine, only 25-OHD and creatinine were independent predictors of PTH.

CONCLUSION

The negative relationship between 25-OHD and PTH is modulated by age but not gender. Desirable 25-OHD levels derived from examining the 25-OHD-PTH relationship should therefore take into account the age of the population of interest.

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.