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Vitamin D (VD), due to its hormonal action, plays a crucial role in calcium homeostasis and bone metabolism, and its deficiency has been associated with musculoskeletal disorders such as osteoporosis, fractures, and osteomalacia, as well as a growing attention of chronic conditions and certain cancers. Despite its physiological relevance and widespread prevalence, particularly among older individuals, patients with chronic diseases, institutionalized populations and pregnant or lactating women, clinical approaches to diagnosing and managing vitamin D deficiency (VDD) remain heterogeneous across guidelines and healthcare settings. This reflects a lack of consensus regarding the benefits and limitations of universal versus selective screening, the definition of adequate serum concentrations, and the clinical indications for supplementation across different patient profiles. This narrative review explores key controversies in the clinical management of VDD, including current perspectives on screening strategies and target populations, indications for empirical supplementation, criteria for biochemical monitoring, and therapeutic goals in bone-related outcomes. In particular, the review discusses the rationale for adopting a 30 ng/mL (75 nmol/L) threshold for adequate serum 25(OH) concentrations in skeletal health, the role of vitamin D and calcium in osteoporosis treatment, and the pharmacological advantages of cholecalciferol compared to other vitamin D compounds. Through a syn

<h4>Objectives</h4>Hip fracture, a critical public health concern in aging populations, are associated with significant morbidity, mortality, and disability and have been referred to as "the last fracture of life." While vitamin D influences bone mineral density (BMD) and fragility fracture risk, its impact on muscle function and its relationship with fracture risk remains underexplored. This study aimed to investigate whether vitamin D deficiency increases hip fracture risk primarily through its effects on muscle function.<h4>Methods</h4>In this retrospective study, 138 patients aged ≥ 50 years with initial low-energy hip fracture treated between January 2024 and June 2024 were compared with 182 community residents aged ≥ 50 years recruited from the hospital physical examination center. Clinical baseline data such as age, sex, and body mass index (BMI), were recorded. Through regression analysis, independent factors influencing hip fracture risk were analyzed. The effects of vitamin D on BMD and muscle function were evaluated using femoral neck areal BMD (FN aBMD) and pectoralis muscle index (PMI), respectively.<h4>Results</h4>Patients with hip fracture were significantly older and had lower BMI, vitamin D level, muscle function, and FN aBMD than controls (P < 0.05). Univariate analysis identified age, BMI, vitamin D, PMI, and FN aBMD as key factors influencing hip fracture risk. After adjusting for age, sex and BMI, vitamin D, PMI, and FN aBMD emerged as independent protect

<h4>Background</h4>Vitamin D deficiency (VDD) has been implicated as a potential risk factor for thyroid cancer; however, existing evidence is derived primarily from case-control or cross-sectional studies. This study aimed to examine the association between pre-diagnostic VDD and the risk of incident thyroid cancer over a 10-year follow-up period.<h4>Methods</h4>This retrospective propensity score-matched cohort study used the TriNetX Global Collaborative Network. Adults aged ≥ 18 y with serum 25-hydroxyvitamin D [25(OH)D] measurements between 2010 and 2023 were classified as having VDD (<20 ng/mL) or vitamin D sufficiency (≥30 ng/mL). One-to-one propensity score matching was performed on demographics, comorbidities, thyroid-related disorders, laboratory values, and vitamin D supplementation. The primary outcome was incident thyroid cancer ascertained ≥ 180 day after the index date (landmark approach) over 10 y of follow-up. Positive (osteoporotic fracture) and negative (appendicitis, goiter) control outcomes and thyroid procedure utilization were evaluated to assess detection bias.<h4>Results</h4>After matching, 571,669 pairs were analyzed over a median follow-up of 6.8 y. VDD was associated with an increased risk of incident thyroid cancer (HR: 1.41; 95% CI: 1.32, 1.50), and this risk was attenuated among patients with vitamin D insufficiency (25[OH]D 20-30 ng/mL; HR: 1.27; 95% CI: 1.20, 1.34), demonstrating a dose-dependent relationship. Thyroid biopsy and ultrasonography

<b>Background/Objectives</b>: Cardiometabolic risk factor clustering is common in older adults and is associated with substantially increased cardiometabolic morbidity and mortality. This study aimed to examine the association between serum 25-hydroxyvitamin D [25(OH)D] status and cardiometabolic risk factor clustering among rural community-dwelling older adults. <b>Methods</b>: This cross-sectional study analyzed data from the 2022 Korea National Health and Nutrition Examination Survey (KNHANES) for 432 adults aged ≥65 years residing in rural areas. Cardiometabolic risk factor clustering was defined as the presence of ≥2 of the following: abdominal obesity, hypertension, type 2 diabetes mellitus, and dyslipidemia. Multivariable logistic regression was performed adjusting for sociodemographic and behavioral factors. <b>Results</b>: Cardiometabolic risk factor clustering was more prevalent among participants with vitamin D deficiency (<15 ng/mL) than among those with sufficient levels (66.0% vs. 44.9%, <i>p</i> = 0.006). After adjustment, vitamin D sufficiency (≥15 ng/mL), compared with vitamin D deficiency (<15 ng/mL), was associated with lower odds of clustering (aOR = 0.422, 95% CI: 0.219-0.811, <i>p</i> = 0.010). Meeting the WHO physical activity guideline was also associated with lower odds of clustering (AOR = 0.450, 95% CI: 0.226-0.897, <i>p</i> = 0.023). <b>Conclusions</b>: Lower vitamin D status was associated with a higher prevalence of cardiometabolic risk factor cl

<b>Background:</b> Reference intervals for 25-hydroxyvitamin D are significantly influenced by seasonal variations and population-specific factors. This study aimed to establish local, population-specific Vitamin D reference intervals using the refineR algorithm and to compare these results with the conventional non-parametric method using a hospital database. <b>Methods:</b> A total of 127,220 laboratory results from 2022 to 2025 were retrospectively analyzed. Data were filtered based on adult age, morning fasting specimens, outpatient status, and normal parathyroid hormone levels (14-72 ng/L). Following filtration, Wilcoxon and Kruskal-Wallis tests were employed to evaluate differences between potential subgroups. Consequently, 24,036 eligible results were stratified by age (18-40, 41-65, and >65 years) and sex (female and male). Reference intervals were calculated using the refineR algorithm and the non-parametric percentile method. <b>Results:</b> The distribution of vitamin D levels was found to be right-skewed [Median: 12.92 ng/mL (4.21-149)]. The upper reference limits obtained via refineR were consistently lower than those derived from the non-parametric method. Both methods showed a linear increase in median values and upper reference limits with advancing age. Females in the 18-40 age group exhibited the lowest vitamin D profile. The summer concentrations were significantly higher than those of other seasons (<i>p</i> <0.05). <b>Conclusions:</b> The refineR algorith

<b>Background:</b> Sjögren's syndrome (SjS) is a chronic systemic autoimmune disease associated with substantial extraglandular morbidity, including osteoporosis, cardiovascular disease, and renal involvement. Vitamin D deficiency (VDD) is highly prevalent in patients with SjS and has been linked to immune dysregulation, systemic inflammation, and adverse cardiorenal outcomes in other clinical settings. However, the prognostic significance of VDD in patients with SjS and osteoporosis remains incompletely characterized. <b>Methods:</b> We conducted a retrospective cohort study using de-identified electronic health records from the TriNetX research network between 2010 and 2024. Adult patients with SjS and osteoporosis who had at least one serum 25-hydroxyvitamin D measurement within six months before or after cohort entry were included. VDD was defined as a serum 25-hydroxyvitamin D concentration below 20 ng/mL, and vitamin D adequacy (VDA) as a concentration of 30 ng/mL or higher. Propensity score matching was performed at a 1: 1 ratio using 95 baseline covariates. The primary outcome was all-cause mortality. Secondary outcomes included major adverse cardiovascular events (MACEs), major adverse kidney events (MAKEs), and fractures. <b>Results:</b> Among 19,177 eligible patients, 1218 with VDD and 7659 with VDA met the inclusion criteria. After propensity score matching, 1067 well-balanced pairs were analyzed. Over five years of follow-up, VDD was associated with higher risks

<h4>Background</h4>Hearing impairment is associated with an elevated risk of depression, yet modifiable risk factors in this population remain poorly characterized. Although vitamin D deficiency (VDD) has been linked to depression in general populations, no large-scale study has examined this association among adults with hearing impairment.<h4>Methods</h4>This retrospective cohort study used the TriNetX Global Collaborative Network. Adults aged ≥18 years with hearing impairment who underwent serum 25-hydroxyvitamin D [25(OH)D] testing between 2010 and 2023 were classified into VDD (< 20 ng/ml) and sufficiency (≥30 ng/ml) cohorts. Thus, the study population represented a selected healthcare-utilizing cohort with available vitamin D measurements. After propensity score matching (48,184 per group), Cox models estimated hazard ratios (HRs) for incident depression over 12 years using a 1-year landmark design.<h4>Results</h4>For the primary outcome, VDD was associated with a significantly higher risk of overall depression (<i>HR</i>, 1.57; 95% <i>CI</i>, 1.51-1.64; <i>P</i> < 0.001). For secondary outcomes, significant associations were observed for depressive episode (<i>HR</i>, 1.60), recurrent depression (<i>HR</i>, 1.62), suicidal behavior/self-harm (<i>HR</i>, 1.47), and all-cause mortality (<i>HR</i>, 1.40; all <i>P</i> < 0.001). The associations remained robust across sensitivity analyses (<i>HRs</i>, 1.55-1.65). Subgroup analyses showed consistent associations across sex,

Blood 25-hydroxyvitamin D (25(OH)D) concentrations vary considerably by season and sex. The present study aimed to determine associations between vitamin D deficiency and mortality in Japanese adults and identify risk thresholds according to 25(OH)D concentrations. This was a cohort study with an 11-year follow-up. Participants were 8285 community-dwelling Japanese adults aged 40-74 years. Plasma 25(OH)D concentrations were measured by chemiluminescent immunoassay at baseline and divided into quintiles for each of the subgroups stratified by season and sex (denoted as season- and sex-stratified quintiles). The main outcome was all-cause mortality. Hazard ratios (HR) were calculated using a Cox proportional hazards model. Mean age and 25(OH)D concentration were 59·9 years (sd = 9·1) and 50·1 nmol/l (sd = 18·1), respectively. Lower season- and sex-stratified quintiles were associated with higher hazards of all-cause mortality (<i>P</i>_{for trend} = 0·0015), with the first quintile (median = 28·2 nmol/l) having a higher HR (HR = 1·46, 95 % CI, 1·13, 1·88) than the highest quintile (reference). When crude quintiles were used, the overall association was similar (<i>P</i>_{for trend} = 0·0027), with the first (median = 28·0 nmol/l) and second (median = 39·7 nmol/l) quintiles having higher HR (HR = 1·40, 95 % CI, 1·06, 1·85 and 1·38, 95 % CI, 1·07, 1·77, respectively) than the reference. The risk threshold difference was estimated to be approximately 10 nmol/l. In

<h4>Introduction</h4>Dementia constitutes a major and rapidly growing public health challenge worldwide. The identification of its risk factors and potential contributors has therefore become a major focus of research. This study aimed to investigate the association between serum 25(OH)D concentration and cognitive performance, as well as the odds of cognitive impairment and documented dementia in a hospitalized geriatric population.<h4>Materials and methods</h4>This cross-sectional study included 1,539 hospitalized individuals aged ≥60 years from Central Poland. Cognitive performance was assessed using the Mini-Mental State Examination (MMSE) and the Clock Drawing Test (CDT). The age- and education-adjusted MMSE score was used in the statistical analyses. The test-based adverse cognitive outcomes were defined separately as MMSE <24, based on the age- and education-adjusted MMSE score, and CDT < 6. Information on documented dementia was obtained from medical records. Univariate analysis was performed using Mann-Whitney <i>U</i> test for continuous variables and chi-square test for categorical variables. Multivariable logistic regression models were used to assess the associations between serum 25(OH)D concentration and MMSE < 24, CDT < 6, and documented dementia, with adjustment for age, sex, BMI, albumin concentration, depressive symptoms, and history of stroke.<h4>Results</h4>Vitamin D deficiency (<20 ng/mL) was present in 53.3% of participants, and only 27.6% had concentra

<h4>Background</h4>Vitamin D deficiency is a common global health problem and remains highly prevalent in Türkiye, where limited food fortification and heterogeneous clinical practices contribute to variability in testing and supplementation strategies.<h4>Aims</h4>To provide Türkiye-specific best practice recommendations for defining clinically relevant serum 25-hydroxyvitamin D [25(OH)D] thresholds, identifying adult risk groups for targeted testing, and recommending evidence-based prevention, treatment, and monitoring approaches while minimizing under-treatment and inappropriate high-dose use.<h4>Methods</h4>This national expert consensus document was developed by endocrinologists from across Türkiye using a structured, modified Delphi methodology. Draft statements informed by systematic literature reviews were rated via online surveys using a 9-point Likert scale, followed by two Delphi rounds and a face-to-face consensus meeting in İstanbul in October 2025.<h4>Results</h4>Recommendations addressed sun exposure, laboratory assessment, screening, supplementation, treatment, and follow-up. Serum 25(OH)D <20 ng/mL was defined as deficiency and <12 ng/mL as severe deficiency, with a target range of 20-50 ng/mL. Routine population-wide screening was not recommended; instead, targeted testing in high-risk adults and symptom-driven biochemical evaluation were endorsed. Empiric supplementation was recommended for selected high-risk groups, with cholecalciferol as the preferred ag

<i>Background and Objectives:</i> Vitamin D deficiency has been implicated in muscle weakness and functional decline among older adults. However, its association with sarcopenia-related impairment, particularly when evaluated using readily available nutritional and functional indicators in routine clinical practice, remains incompletely understood. <i>Materials and Methods:</i> This retrospective cross-sectional study included 148 adults aged ≥65 years who attended a Physical Medicine and Rehabilitation outpatient clinic. Sarcopenia-related risk was classified using an EWGSOP2-informed operational framework based on handgrip strength together with nutritional and functional indicators available in the retrospective dataset. Serum 25-hydroxyvitamin D [25(OH)D] concentrations were measured using a chemiluminescent microparticle immunoassay. Group comparisons, correlation analyses, and multivariable logistic regression analyses were performed. <i>Results:</i> The prevalence of probable sarcopenia and probable sarcopenia with nutritional/functional risk indicators was significantly higher among participants with vitamin D deficiency. Serum 25(OH)D levels differed significantly across the three study groups (<i>p</i> < 0.001). Post-hoc Tukey analysis demonstrated significantly lower serum 25(OH)D concentrations in the probable sarcopenia with nutritional/functional risk indicators group than in both the no sarcopenia and probable sarcopenia groups (both <i>p</i> < 0.001). Serum 25

<h4>Background and objectives</h4>Low serum 25-hydroxyvitamin D (25OHD) has been associated with osteoporosis and osteoporotic fracture, but whether these associations are causal remains unclear.<h4>Methods</h4>We identified 15 single-nucleotide polymorphisms (SNPs) affecting serum 25OHD levels in seven genes in the peripheral blood genomic deoxyribonucleic acid (DNA) of 2061 community-based people aged 20-92 years (711 men and 1350 women) and 200 outpatients aged 55-85 years with vertebral fractures (36 men and 164 women). Our study employs Mendelian randomization (MR) to determine the causal relationship between serum 25OHD concentration and bone mineral density (BMD), bone turnover markers (BTMs), and vertebral fracture.<h4>Results</h4>MR analysis indicated no correlation between hereditary 25OHD levels and BMD, procollagen type 1 N-terminal propeptide (P1NP), carboxy-terminal telopeptide of type 1 collagen (CTX), and vertebral fractures (all <i>P</i> > 0.05) in all participants. In participants aged 55-92 years, MR analysis revealed that low serum 25OHD levels (odds ratio [OR] = 1.38; 95% confidence interval [CI]: 1.07-1.79; <i>P</i> = 0.014) are causally associated with increased P1NP levels. In sensitivity analysis, MR-Egger regression and the Weighted-median estimator indicated no significant pleiotropy.<h4>Conclusions</h4>Our findings suggest that baseline 25OHD levels are unlikely to have a large effect on risk of vertebral fractures. Larger MR studies and randomized

<b>Background/Objectives:</b> Vitamin D deficiency remains common in UVB-constrained, pollution-exposed, sedentary, and ageing populations, yet recent guidelines discourage routine screening and empiric high-dose supplementation in generally healthy adults. This review clarifies the clinical distinction between untargeted population supplementation and monitored repletion of documented deficiency in high-risk individuals. Methods: We conducted a focused narrative review of PubMed/MEDLINE, Scopus, Web of Science, and the Cochrane Library. The focused evidence search supporting the narrative synthesis was completed in June 2026. References published subsequently were included during manuscript preparation only when relevant for contextual purposes and were not incorporated retrospectively into the evidence-selection process underlying the review's clinical conclusions. Evidence was interpreted according to baseline and achieved 25-hydroxyvitamin D [25(OH)D], dosing schedule, route, body composition, endpoint, and population risk. No formal risk-of-bias assessment, certainty grading, or systematic meta-analytic synthesis was performed. <b>Key Findings:</b> The strongest rationale for vitamin D repletion remains musculoskeletal, particularly for osteomalacia, muscle function, osteoporosis care, and fracture-related vulnerability in deficient or high-risk patients. Management should separate generally healthy adults from patients with an indication for testing or treatment. Histor

Osteoporosis is a progressive skeletal disorder characterized by decreased bone strength and an increased risk of fractures. It presents a high global prevalence, thus imposing a significant clinical and economic burden. This narrative review includes current evidence on the role of combined calcium and vitamin D supplementation in the management and prevention of osteoporosis, as well as its effect on reducing fracture risk and maintaining bone mineral density. It aims to provide an overview of osteoporosis pathophysiology, the importance of adequate calcium levels and 25-hydroxyvitamin D concentrations and the prevalence of their deficiencies. The review examines the evidence supporting combined supplementation and its importance in patients receiving anti-osteoporotic pharmacological therapies. Current clinical guidelines and consensus statements, along with their recommendations for dosing, formulation, and monitoring of calcium and vitamin D supplements, are included. Barriers to the effective implementation, gaps in clinical practice, patient adherence, and primary care challenges are discussed. Ultimately, this review examines the cost-effectiveness of supplementation and the areas for improvement in real-world evidence and research in the field of osteoporosis. This work aims to provide clinicians and healthcare professionals with an updated, evidence-based framework for optimizing calcium and vitamin D supplementation in the care of patients with osteoporosis.

<h4>Background</h4>Vitamin D deficiency in older adults may impair muscle function and physical performance. This prospective observational cohort study examined the 12-month outcomes of vitamin D supplementation, delivered as part of routine clinical care, in older adults with vitamin D deficiency compared with an insufficiency comparison group.<h4>Methods</h4>A total of 194 participants aged ≥60 years were enrolled: 164 with vitamin D deficiency (25(OH)D <20 ng/mL; supplementation group) and 30 with insufficiency (20-29 ng/mL; comparison group). The supplementation group received supplementation targeting 25(OH)D >30 ng/mL; the comparison group received no supplementation. The Handgrip Strength Test (HGS), the Gait Speed Test (GST), the Short Physical Performance Battery Test (SPPB), and the Timed Up and Go Test (TUG) were assessed at baseline and 12 months.<h4>Results</h4>Supplementation raised 25(OH)D by 142.9% versus 5.4% in the comparison group (<i>p</i> < 0.001). For the primary outcome, the supplementation group showed a 16.2% increase in the HGS versus no change in the comparison group (<i>p</i> < 0.001; ANCOVA partial η² = 0.284). For the secondary outcomes, the comparison group was associated with a significant functional decline relative to the supplementation group: the median change on the SPPB in the comparison group was 0.0% (IQR: -8.7, 0.0; between-group <i>p</i> < 0.001) and the TUG worsened by +3.2% (between-group <i>p</i> < 0.001), while the sup

<i>Background and Objectives:</i> Vitamin D deficiency is common in older adults with hip fracture and has been associated with adverse postoperative outcomes. However, heterogeneity in deficiency thresholds, outcome definitions, and patient populations has complicated the interpretation and clinical application of existing evidence. This narrative review aimed to summarize current evidence regarding perioperative vitamin D status, its associations with postoperative complications, mortality, functional recovery, and secondary fracture, and the role of vitamin D supplementation after hip fracture. <i>Materials and Methods:</i> Relevant studies were identified through PubMed searches and manual screening of reference lists. Cohort studies, randomized controlled trials, systematic reviews, meta-analyses, and clinical guidelines addressing vitamin D status, supplementation, hip fracture outcomes, fracture prevention, or postoperative recovery in older adults were narratively synthesized. <i>Results:</i> Low serum 25-hydroxyvitamin D was associated with selected early medical complications, mortality, impaired functional recovery, and secondary hip fracture, although these associations varied across outcomes. The strongest prognostic associations with mobility were observed in patients with severe deficiency (approximately ≤10-12 ng/mL), whereas mild insufficiency showed less consistent associations. Heterogeneity among studies reflected differences in deficiency thresholds, samp