Vitamin D status and its association with parathyroid hormone in 23,134 outpatients

The Optimal Protective 25-Hydroxyvitamin D Level for Different Health Outcomes in Adults: A Brief Summary of Dose-Response Meta-Analyses

Vitamin D is very important for bone metabolism as well as for the prevention of various diseases, such as type 2 diabetes, cardiovascular disease and different types of cancer. Although vitamin D deficiency is widespread and an important public health problem, there exists controversy in the scientific community, with no established standard definition of adequate and deficient vitamin D status. To add new information on this topic, the aim of this brief opinion paper is to identify and discuss the optimal 25(OH)D concentration (range) for a reduction in the risk of various disease outcomes by summarizing dose-response reporting meta-analyses.

Implications of high-dose vitamin D3 with and without vitamin C on bone mineralization and blood biochemical factors in broiler breeder hens and their offspring

As broiler breeder hens age, they often experience a decline in bone mineralization and calcium absorption, especially during the later stages of egg production. This issue not only affects the hens' health, making them more prone to conditions like osteoporosis, but it also impacts the quality of their offspring. To tackle this problem, our study explores whether supplementing these hens with a combination of vitamins D3 and C could help improve their bone health and overall biochemical balance, both for them and their progeny. The goal of this research was to evaluate the effects of high doses of vitamin D3, with and without added vitamin C, on bone mineralization and key blood parameters in aging broiler breeder hens and their offspring. In this experiment, 240 hens and 24 roosters from the Ross 308 strain, aged between 49 and 61 weeks, were used, and a two-way ANOVA (2 × 2) design was applied. This involved two levels of vitamin D3 (3,500 IU and 5,500 IU) and two levels of vitamin C (0 and 150 mg/kg), with six replications of 10 hens and one rooster per group. At the end of the study, blood samples were collected from hens and their offspring for biochemical analysis, and tibia bones were taken for ash content and mineralization assessment. The findings showed that vitamin D3 supplementation significantly lowered blood cholesterol, alkaline phosphatase (ALP), and parathyroid hormone (PTH) levels (P < 0.05), while boosting calcium, 25-hydroxycholecalciferol (25(OH)D3), and 1,25-dihydroxycholecalciferol (1,25(OH)2D3) (P < 0.05). Higher doses of vitamin D3 also improved the strength, resistance, and ash content of the hens' tibia bones, and increased calcium in the carcasses of their offspring. Adding 150 mg/kg of vitamin C to the diet also had a positive effect, reducing cholesterol, ALP, and PTH, while enhancing plasma calcium, total antioxidant capacity, and the active form of vitamin D3 (P < 0.05). Vitamin C supplementation significantly strengthened the tibial bones of the hens and improved plasma calcium and PTH levels in their offspring (P < 0.05). Interestingly, combining elevated doses of both vitamins D3 and C resulted in even greater improvements in tibial bone strength (P < 0.05). In conclusion, giving hens 150 mg of vitamin C along with 5,500 IU of vitamin D3 leads to substantial improvements in the calcium content and structural integrity of their bones, and also boosts calcium and ash content in the carcasses of their offspring.

The vitamin D3 hormone, 1,25(OH)2D3, regulates fibroblast growth factor 23 (FGF23) production in human skin cells

The bone hormone fibroblast growth factor 23 (FGF23) regulates renal phosphate reabsorption and the enzymatic production of active vitamin D3 [1,25(OH)2D3]. Therefore, FGF23 production in bone cells is closely regulated by 1,25(OH)2D3 acting via the vitamin D receptor (VDR). Skin cells can produce hydroxyvitamin D3 metabolites from its precursor D3 made through ultraviolet B light exposure. Interestingly, the expression of Fgf23 has been found in rodent skin, but its expression, regulation, and role in human skin are unclear. Therefore, we investigated whether hydroxyvitamin D3 metabolites regulate FGF23 in human skin cells. Primary adult and neonatal epidermal keratinocytes (HEKn), melanocytes (HEMn), dermal fibroblasts (HDFn), as well as human melanoma cells, HaCaT, HaCaT VDR KO, and A431 epidermoid cells, were used to assess FGF23 gene expression (quantitative reverse-transcription real-time PCR), cellular FGF23 protein (Western blot), or secreted FGF23 protein (ELISA) after treatment with hydroxyvitamin D3 metabolites. HaCaT cells treated with recombinant FGF23 were used to explore its function in skin. Human skin cells can synthesize FGF23. Treatment with 1,25(OH)2D3 significantly increased FGF23 mRNA levels in HaCaT and HDFn cells, and moderately in HEKn cells, mediated in part by the VDR. It also moderately enhanced mRNA levels of the FGF23-processing enzyme GALNT3 and stimulated secretion of hormonally active FGF23 from HaCaT cells. Treatment of HaCaT cells with FGF23 increased mRNA levels of the cholesterol- and vitamin D-metabolizing enzymes, CYP11A1 and CYP27A1. In conclusion, human skin cells express and secrete FGF23, which is regulated by 1,25(OH)2D3 acting in part by the VDR. FGF23 affects the expression of cutaneous sterol-metabolizing enzymes.NEW & NOTEWORTHY This study shows for the first time the expression and secretion of the FGF23 hormone by human skin cells. In addition, we identified the active vitamin D3 hormone, 1,25(OH)2D3, to be a potent regulator of dermal FGF23 expression and protein secretion, partly involving the vitamin D receptor. Furthermore, we provide initial evidence demonstrating that FGF23 upregulates the gene expression of CYP11A1 and CYP27A1 in keratinocytes.

Predicting Tumor Volume in Primary Hyperparathyroidism From Preoperative Clinical Data

CONTEXT

Primary hyperparathyroidism (PHPT) is an endocrine disorder that is treated surgically, and some correlation between the size of the responsible lesion and preoperative clinical data is assumed.

OBJECTIVE

The purpose of this study was to predict tumor volume of the lesion responsible for PHPT from preoperative clinical data.

METHODS

Participants comprised patients with surgically treated PHPT who underwent initial surgery in our department between January 2000 and December 2021. The volume of parathyroid gland removed was used as the primary outcome and associations with preoperative clinical data were assessed by multivariable analysis.

RESULTS

A positive correlation was identified between parathyroid tumor volume and both preoperative intact parathyroid hormone (PTH) (Spearman's r = 0.503) and calcium values (Spearman's r = 0.338). Data for intact PTH value and tumor volume were logarithmically transformed (ln-PTH = log-transformed intact PTH value; ln-volume = log-transformed tumor volume). Multiple regression analysis revealed male sex, ln-PTH and calcium values as significant predictors of ln-volume, with standardized regression coefficients of 0.213 (95% CI 0.103-0.323), 0.5018 (95% CI 0.4442-0559), and 0.322 (95% CI 0.0339-0.149), respectively. The adjusted R2 for this model is 0.320.

CONCLUSION

Preoperative serum intact PTH value is associated with tumor volume of the lesion responsible for PHPT. A rough estimation of the tumor size would provide responsible physicians with opportunities to add further imaging tests or plan appropriate surgical strategies.

Does higher serum 25-hydroxyvitamin D levels will harm bone mineral density?: a cross-sectional study

OBJECTIVE

Vitamin D plays a critical role in the prevention and management of osteoporosis. However, there is an ongoing debate regarding the most effective vitamin D supplementation strategies for maintaining optimal bone mineral density (BMD) levels in adults. This study sought to establish the correlation between serum 25-hydroxyvitamin D [25(OH)D] levels and total BMD in a substantial population sample.

METHODS

Data from the National Health and Nutrition Examination Survey (NHANES) for the 2011-2018 cycles, encompassing 11,375 adult participants, were analyzed. The primary variables of interest were serum 25(OH)D levels and BMD. A multivariable logistic regression model was utilized to account for relevant variables associated with these correlations.

RESULTS

A U-shaped relationship between serum 25(OH)D levels and BMD was observed. In males, a significant positive association was identified for 25(OH)D levels below 84.8 nmol/L (p < 0.0001), while levels above this threshold showed no significant correlation (p = 0.3377). In females, those with 25(OH)D levels below 31.4 nmol/L exhibited a significant positive association with BMD (p = 0.0010), but this association weakened and became marginally significant above this threshold (p = 0.0650).

CONCLUSIONS

For adult males, the optimal serum 25(OH)D level is 84.8 nmol/L, beyond which higher levels do not lead to increased BMD. A deficiency threshold for adult females should be above 31.4 nmol/L, as lower 25(OH)D levels are not conducive to BMD. These findings underscore the importance of maintaining appropriate vitamin D levels for bone health in both genders.

Target Values for 25-Hydroxy and 1,25-Dihydroxy Vitamin D Based on Their Associations with Inflammation and Calcium-Phosphate Metabolism

Target values for 25-hydroxy vitamin D and 1,25(OH)2D or 1,25-dihydroxy vitamin D remain a topic of debate among clinicians. We analysed data collected from December 2012 to April 2020 from two cohorts. Cohort A, comprising 455,062 subjects, was used to investigate the relationship between inflammatory indicators (white blood cell [WBC] count and C-reactive protein [CRP]) and 25(OH)D/1,25(OH)2D. Cohort B, including 47,778 subjects, was used to investigate the connection between 25(OH)D/1,25(OH)2D and mineral metabolism markers (phosphate, calcium, and intact parathyroid hormone [iPTH]). Quadratic models fit best for all tested correlations, revealing U-shaped relationships between inflammatory indicators and 25(OH)D and 1,25(OH)2D. Minimal CRP and WBC counts were observed at 1,25(OH)2D levels of 60 pg/mL and at 25(OH)D levels of 32 ng/mL, as well as of 42 ng/mL, respectively. iPTH correlated inversely with both 1,25(OH)2D and 25(OH)D, while phosphate as well as calcium levels positively correlated with both vitamin D forms. Calcium-phosphate product increased sharply when 25(OH)D was more than 50 ng/mL, indicating a possible risk for vascular calcification. Multiple regression analyses confirmed that these correlations were independent of confounders. This study suggests target values for 25(OH)D between 30-50 ng/mL and for 1,25(OH)2D between 50-70 pg/mL, based particularly on their associations with inflammation but also with mineral metabolism markers. These findings contribute to the ongoing discussion around ideal levels of vitamin D but require support from independent studies with data on clinical endpoints.

Vitamin D deficiency or resistance and hypophosphatemia

Vitamin D is mainly produced in the skin (cholecalciferol) by sun exposure while a fraction of it is obtained from dietary sources (ergocalciferol). Vitamin D is further processed to 25-hydroxyvitamin D and 1,25-dihydroxy vitamin D (calcitriol) in the liver and kidneys, respectively. Calcitriol is the active form which mediates the actions of vitamin D via vitamin D receptor (VDR) which is present ubiquitously. Defect at any level in this pathway leads to vitamin D deficient or resistant rickets. Nutritional vitamin D deficiency is the leading cause of rickets and osteomalacia worldwide and responds well to vitamin D supplementation. Inherited disorders of vitamin D metabolism (vitamin D-dependent rickets, VDDR) account for a small proportion of calcipenic rickets/osteomalacia. Defective 1α hydroxylation of vitamin D, 25 hydroxylation of vitamin D, and vitamin D receptor result in VDDR1A, VDDR1B and VDDR2A, respectively whereas defective binding of vitamin D to vitamin D response element due to overexpression of heterogeneous nuclear ribonucleoprotein and accelerated vitamin D metabolism cause VDDR2B and VDDR3, respectively. Impaired dietary calcium absorption and consequent calcium deficiency increases parathyroid hormone in these disorders resulting in phosphaturia and hypophosphatemia. Hypophosphatemia is a common feature of all these disorders, though not a sine-qua-non and leads to hypomineralisation of the bone and myopathy. Improvement in hypophosphatemia is one of the earliest markers of response to vitamin D supplementation in nutritional rickets/osteomalacia and the lack of such a response should prompt evaluation for inherited forms of rickets/osteomalacia.

Threshold of 25(OH)D and consequently adjusted parathyroid hormone reference intervals: data mining for relationship between vitamin D and parathyroid hormone

PURPOSE

By recruiting reference population, we aimed to (1): estimate the 25(OH)D threshold that maximally inhibits the PTH, which can be defined as the cutoff value for vitamin D sufficiency; (2) establish the PTH reference interval (RI) in population with sufficient vitamin D.

METHODS

Study data were retrieved from LIS (Laboratory Information Management System) under literature suggested criteria, and outliers were excluded using Tukey fence method. Locally weighted regression (LOESS) and segmented regression (SR) were conducted to estimate the threshold of 25(OH)D. Multivariate linear regression was performed to evaluate the associations between PTH concentration and variables including 25(OH)D, gender, age, estimated glomerular filtration rate (EGFR), body mass index (BMI), albumin-adjusted serum calcium (aCa), serum phosphate(P), serum magnesium(Mg), and blood collection season. Z test was adopted to evaluate whether the reference interval should be stratified by determinants such as age and gender.

RESULTS

A total of 64,979 apparently healthy subjects were recruited in this study, with median (Q1, Q3) 25(OH)D of 45.33 (36.15, 57.50) nmol/L and median (Q1, Q3) PTH of 42.19 (34.24, 52.20) ng/L. The segmented regression determined the 25(OH)D threshold of 55 nmol/L above which PTH would somewhat plateau and of 22 nmol/L below which PTH would rise steeply. Multivariate linear regression suggested that gender, EGFR, and BMI were independently associated with PTH concentrations. The PTH RI was calculated as 22.17-72.72 ng/L for subjects with 25(OH)D ≥ 55 nmol/L with no necessity of stratification according to gender, age, menopausal status nor season.

CONCLUSION

This study reported 25(OH)D thresholds of vitamin D sufficiency at 55 nmol/L and vitamin D deficiency at 22 nmol/L, and consequently established PTH RIs in subjects with sufficient vitamin D for northern China population for the first time.

Inverse correlation of intact PTH, oxidized PTH as well as non-oxidized PTH with 25-hydroxyvitamin D3 in kidney transplant recipients

Background

25-hydroxyvitamin D (25(OH)D) and potentially also 1,25-dihydroxyvitamin D (1,25(OH)2D) inhibits the synthesis of parathyroid hormone (PTH) in the chief cells of the parathyroid gland. Clinical studies showing a negative correlation between (25(OH)D and PTH are in good agreement with these findings in basic science studies. However, PTH was measured in these studies with the currently clinically used 2nd or 3rd generation intact PTH (iPTH) assay systems. iPTH assays cannot distinguish between oxidized forms of PTH and non-oxidized PTH. Oxidized forms of PTH are the by far most abundant form of PTH in the circulation of patients with impaired kidney function. Oxidation of PTH causes a loss of function of PTH. Given that the clinical studies done so far were performed with an PTH assay systems that mainly detect oxidized forms of PTH, the real relationship between bioactive non-oxidized PTH and 25(OH)D as well as 1,25(OH)2D is still unknown.

Methods

To address this topic, we compared for the first time the relationship between 25(OH)D as well as 1,25(OH)2D and iPTH, oxPTH as well as fully bioactive n-oxPTH in 531 stable kidney transplant recipients in the central clinical laboratories of the Charité. Samples were assessed either directly (iPTH) or after oxPTH (n-oxPTH) was removed using a column that used anti-human oxPTH monoclonal antibodies, a monoclonal rat/mouse parathyroid hormone antibody (MAB) was immobilized onto a column with 500 liters of plasma samples. Spearman correlation analysis and Multivariate linear regression were used to evaluate the correlations between the variables.

Results

There was an inverse correlation between 25(OH)D and all forms of PTH, including oxPTH (iPTH: r=-0.197, p<0.0001; oxPTH: r=-0.203, p<0.0001; n-oxPTH: r=-0.146, p=0.001). No significant correlation was observed between 1,25(OH)2D and all forms of PTH. Multiple linear regression analysis considering age, PTH (iPTH, oxPTH and n-oxPTH), serum calcium, serum phosphor, serum creatinine, fibroblast growth factor 23 (FGF23), osteoprotegerin (OPG), albumin, and sclerostin as confounding factors confirmed these findings. Subgroup analysis showed that our results are not affected by sex and age.

Conclusion

In our study, all forms of PTH are inversely correlated with 25-hydroxyvitamin D (25(OH)D). This finding would be in line with an inhibition of the synthesis of all forms of PTH (bioactive n-oxPTH and oxidized forms of PTH with minor or no bioactivity) in the chief cells of the parathyroid glad.

Vitamin D supplementation in the treatment of polycystic ovary syndrome: A meta-analysis of randomized controlled trials

Background

Vitamin D level is closely associated with the development of polycystic ovary syndrome (PCOS). We aimed to systematically evaluate the effects of vitamin D supplementation on patients with PCOS, to provide reliable evidence to the clinical treatment of PCOS.

Methods

We searched PubMed, Medline, EMbase, Cochrane Library, Web of Science, WanFang, China national knowledge infrastructure(CNKI) and Weipu databases for randomized controlled trials (RCTs) on vitamin D supplementation for the treatment of PCOS. Two reviewers independently screened literature, extracted data and evaluated the risk of bias of included RCTs. RevMan 5.3 software was used for meta-analysis.

Results

13 RCTs with 840 PCOS patients were included finally. Meta-analyses indicated that vitamin D supplementation increase the serum vitamin D level[mean difference(MD) = 17.81, 95% confidence interval(CI) (10.65, 24.97)] and endometrial thickness [MD = 1.78, 95%CI (0.49, 3.06), P = 0.007], reduce the serum hs-CRP [MD = -0.54, 95%CI (-1.00, -0.08)], parathyroid hormone[MD = -14.76, 95%CI (-28.32, -1.19)], total cholesterol[MD = -12.00, 95%CI (-18.36, -5.56)] and total testosterone level [MD = -0.17, 95%CI (-0.29, -0.05)] (all p < 0.05). No significant differences in the SHBG level [MD = 1.33, 95%CI (-2.70, 5.36)] and mF-G score [MD = 0.04, 95%CI (-0.79, 0.86)] between vitamin D and control group were found (all p > 0.05). Egger's tests showed that there were no publication biases in every synthesized result (all P > 0.05).

Conclusion

Vitamin D may be helpful to improve the endocrine and metabolism-related indexes in patients with PCOS. More high-quality studies with larger sample size are warranted to further evaluate the role of vitamin D supplementation in patients with PCOS.

Vitamin D Status in Critically Ill Patients with SIRS and Its Relationship with Circulating Zn and Related Parameters during ICU Stay

Critically ill patients are exposed to different stressors which may generate Systemic Inflammatory Response Syndrome (SIRS). This situation hinders the assessment of micronutrients status, such as vitamin D or Zinc (Zn), potentially affecting patients’ treatment and recovery. The aim of the present study was to assess the evolution of circulating 25–Hydroxyvitamin D (25–OH–D) levels after seven days of Intensive Care Unit (ICU) stay and the influence on changes in plasma and erythrocyte Zn levels, as well as other parameters related to phosphorus–calcium metabolism. A prospective analytical study was conducted on 65 critically ill patients (42% women) aged 31–77 years with SIRS. Total 25–OH–D levels were measured in plasma samples by liquid chromatography-tandem mass spectrometry, and Zn content was analyzed by flame atomic absorption spectrometry. Both 25–OH–D and 25–OH–D₃ levels were directly associated with erythrocyte Zn concentration at follow-up (p = 0.046 and p = 0.011, respectively). A relationship between erythrocyte and plasma Zn was also found at this follow-up point. No such clear associations were found when considering 25–OH–D₂. Different disturbances in levels of phosphorus–calcium metabolism parameters were found, suggesting a relationship between the changes of 25–OH–D₃ levels and parathormone (p = 0.019) and phosphorus (p = 0.005). The findings of the present study suggest an interaction between vitamin D and Zn, in which the correct status of these micronutrients could be a potentially modifiable factor and a beneficial approach in the recovery of critically ill patients.