Evaluating adherence, tolerability and safety of oral calcium citrate in elderly osteopenic subjects: a real-life non-interventional, prospective, multicenter study.

BACKGROUND: Osteoporosis is a common concern in the elderly that leads to fragile bones. Calcium supplementation plays a crucial role in improving bone health, reducing fracture risk, and supporting overall skeletal strength in this vulnerable population. However, there is conflicting evidence on the safety of calcium supplements in elderly individuals. AIM: The aim of this study was to evaluate the adherence, safety and tolerability of calcium citrate supplementation in elderly osteopenic subjects. METHODS: In this non-interventional, prospective, multicenter study, subjects received daily 500 mg calcium citrate supplementation for up to one year. Adherence was calculated based on compliance and persistence. Safety was assessed through adverse reactions (ARs), deaths, and clinical laboratory evaluations. RESULTS: A total of 268 Caucasian subjects (91.4% female, mean age 70 ± 4.5 years) participated in the study. Mean adherence to treatment was 76.6 ± 29.5% and half of subjects had an adherence of 91% and ~ 33% of participants achieved complete (100%) adherence. ARs were reported by nine (3.9%) subjects, primarily gastrointestinal disorders, with no serious ARs. The frequency of all adverse events (including ARs) was significantly higher in subjects with adherence of < 80% (41.6%; 32/77) vs. those with adherence ≥ 80% (11%; 16/145, p < 0.0001). Both systolic and diastolic blood pressure decreased from baseline to follow-up visit (change of -2.8 ± 13.9 mmHg, p = 0.0102 and -2.1 ± 10.4 mmHg, p = 0.0116, respectively). CONCLUSION: This study demonstrated favorable adherence to calcium citrate supplementation in elderly osteopenic subjects. The occurrence of ARs, though generally mild, were associated with lower adherence to calcium supplementation.

ECHOCARDIOGRAPHIC FINDINGS IN PATIENTS WITH NORMOCALCEMIC PRIMARY HYPERPARATHYROIDISM COMPARED WITH FINDINGS IN HYPERCALCEMIC PRIMARY HYPERPARATHYROID PATIENTS AND CONTROL SUBJECTS.

OBJECTIVE: There are no data regarding echocardiographic parameters in patients with normocalcemic primary hyperparathyroidism (NCPHPT). We compared the echocardiographic findings in postmenopausal women with NCPHPT with those in patients with hypercalcemic primary hyperparathyroidism (PHPT) and controls. METHODS: Seventeen consecutive Caucasian postmenopausal women with NCPHPT were compared with 20 women with hypercalcemic PHPT and 20 controls. Obesity, diabetes, kidney failure, and previous cardiovascular diseases were considered exclusion criteria. Each patient underwent biochemical evaluation, bone mineral density scan, and echocardiographic measurements. Patients with parathyroid disorders underwent kidney ultrasound evaluation. RESULTS: Patients with PHPT had significantly higher mean total serum calcium, ionized calcium, 24-hour urinary calcium, and parathyroid hormone and lower mean phosphorus levels compared with those in the controls (all P < .05). The only differences between patients with NCPHPT and PHPT were significantly lower mean total serum calcium, ionized calcium, and 24-hour urinary calcium and higher phosphorus levels in patients with NCPHPT (all P < .05). The only biochemical difference between patients with NCPHPT and the controls was a higher level of mean parathyroid hormone in patients with NCPHPT. There were no differences in cardiovascular risk factors between patients with NCPHPT and PHPT and the controls. Hypertension was the most frequent cardiovascular risk factor, diagnosed in 65% of patients with PHPT. This high prevalence was not statistically significant compared with that observed in patients with NCPHPT (59%) and in the controls (30%). Echocardiography parameters were not different between patients with NCPHPT and PHPT and the controls when subdivided according to the presence of hypertension (ANOVA followed by Bonferroni correction). CONCLUSION: In a population with a low cardiovascular risk, we found no differences in cardiovascular risk factors and echocardiographic parameters between patients with NCPHPT and PHPT and the controls.

Investigating subtle kidney injury in primary hyperparathyroidism by means of sensitive and specific biomarkers.

OBJECTIVE: Kidney involvement is a common complication in primary hyperparathyroidism (PHPT). No study so far has assessed the prevalence of kidney injury developing before the reduction in glomerular filtration rate (GFR) in PHPT. The study was aimed at establishing the potential role of biomarkers of kidney injury in detecting subtle renal damage in patients with PHPT. DESIGN: Cross-sectional study. PATIENTS: A total of 69 postmenopausal patients with PHPT and 41 healthy age- and sex-matched subjects were studied. Exclusion criteria were as follows: GFR < 30 mL/min, chronic inflammatory disease, nephrotic syndrome, infection, malignancy, heart failure, recent exposure to iodinated contrast media or nonsteroidal anti-inflammatory drugs. MEASUREMENTS: We measured a panel of sensitive biomarkers of kidney injury in PHPT vs controls. RESULTS: Mean FGF23 and Klotho were higher in PHPT (72 ± 48 and 811 ± 366 pg/mL, respectively) than controls (53 ± 23.5 and 668.6 ± 17; P < .02 and P < .05). Urine KIM-1/uCr was significantly higher in PHPT (1.4-6  ± 1.3-6 ) than controls (9.2-7  ± 7-7 ; P < .05); this was particularly evident in the CrCl 60-89 mL/min category (1.36  ± 97 vs 8.2-7  ± 3.6-7 ; P < .02). Mean values of urine NGAL/uCr were higher in PHPT with (n = 28) compared to those without kidney stones (n = 35; 1.8-5  ± 1.4-5 and 1-5  ± 8-6 ; P < .0001). We found significant positive associations between urine NGAL/uCr and Ca (R = .292, P < .02) and urine KIM1/uCr and PTH (R = .329, P < .01). CONCLUSIONS: We propose the utilization of these molecules, particularly urine KIM-1/uCr and urine NGAL/uCr ratios for the assessment of subtle kidney injury in patients with PHPT. These molecules are elevated in tubular necrosis and have potential role in the development of kidney damage in PHPT, according to the severity of the disease.

A Challenging Case of Tumor-Induced Osteomalacia: Pathophysiological and Clinical Implications.

We investigated the usefulness of fibroblast growth factor 23 (FGF23) intraoperative assay to monitor tumor resection in patients with oncogenic osteomalacia. A 33-year-old man with 5 years' history of lumbar and pelvis pain together with multiple vertebral fractures was admitted to our hospital. He was diagnosed with ankylosing spondylitis 1 year before. Laboratory investigation showed low tubular reabsorption of phosphate (0.41 mmol/L) despite chronic hypophosphatemia (0.39/L). Increased plasma values of FGF23 (673 pg/mL; n.v. < 95 pg/mL) were also observed. A full-body CT scan showed two suspicious areas in the head of the right femur and in the right tibia; however, the Octreoscan™ showed an increased uptake of the tracer only in the femur. We decided to remove first the head femur lesion and perform intraoperative FGF23 assay to confirm tumor resection; if this had been unsuccessful, we would have extended the operation to excise the second bone lesion. FGF23 basal values and 10, 60, and 225 min after excision of the femoral head were 423, 127, 56, and 30 pg/mL, respectively. The brisk fall of FGF23 values suggested that the head femur lesion was responsible for the syndrome. Histological examination revealed a mesenchymal highly vascular tumor. This is the first report showing the possibility of intraoperative FGF23 assay to monitor tumor resection in patients with tumor-induced osteomalacia.

Effect of a single intravenous zoledronic acid administration on biomarkers of acute kidney injury (AKI) in patients with osteoporosis: a pilot study.

AIMS: The pilot study was designed to evaluate the early effect of intravenous (i.v.) zoledronic acid (ZA) on renal function. METHODS: Five mg i.v. ZA was administered to 23 patients with osteoporosis (17 women and 6 men, mean age 73 ± 7 SD years). Urinary NGAL, KIM-1, and MCP-1, plasma (p) MCP-1 and serum (s) IL-18, serum calcium (sCa), Creatinine clearance (CrCl), parathyroid hormone (PTH), plasma C-terminal FGF23 (pFGF23), serum (s) Klotho, calcium excretion (CaEx) and renal threshold phosphate concentration/GFR (TmPO4 /GFR) were assessed at baseline, 24 h and Day 30 after administration. RESULTS: There was a significant decrease in sCa and CaEx at 24 h (-4.1 ± 2.8%, P < 0.01 and -28 ± 59%, P < 0.05, respectively) and Day 30 (-3.9 ± 4%, P < 0.001 and -26 ± 43%, P < 0.01) and a significant increase in PTH (79.8 ± 95.8%) at Day 30 (P < 0.001) compared to baseline. TmPO4 /GFR decreased significantly at 24 h and Day 30 (-8.6 ± 15.9%, P < 0.05 and -11.3 ± 13.5%, P < 0.001) compared to baseline. We observed no difference in the concentration of pFGF23, sKlotho and urinary AKI biomarkers at any time points. Mean levels of sIL-18 and pMCP-1 increased significantly at 24 h (44 ± 88%; P < 0.01 and 198 ± 237%; P < 0.001) and returned to baseline at Day 30. CONCLUSIONS: Our pilot study suggests that there is no direct acute effect of ZA on kidney function. The increase in plasma MCP-1 and serum IL-18 concentration could be associated with the stimulation of immunity mechanisms occurring soon after the administration of the drug. Secondary hyperparathyroidism develops shortly after the infusion of ZA and is maintained even after 1 month.

Bone loss after discontinuation of denosumab: the devil is in the details.

A 47-year-old postmenopausal woman with osteoporosis was treated with denosumab, which was discontinued due to side effects. She was therefore transitioned to a yearly intravenous infusion of zoledronic acid. An increase in bone turnover markers together with bone loss at the lumbar spine was observed before the second infusion, suggesting an overshooting of bone resorption due to denosumab discontinuation. On physical examination, the patient was restless and reported having lost about 10 kg since the last visit. A solitary left inferior thyroid nodule was noted on neck palpation. Circulating thyroid hormone levels were elevated, with suppressed thyroid-stimulating hormone. A thyroid scan showed increased uptake in the left inferior nodule with suppression of the remainder of the thyroid gland. A diagnosis of hyperthyroidism due to toxic adenoma was made. The patient was treated with radioactive iodine ablation, with consequent complete normalization of thyroid function. She continued yearly treatment with zoledronic acid. She remained clinically well with no further fractures. Bone turnover markers were appropriately suppressed and bone mineral density increased in the spine and hip. This case illustrates how the overshooting phenomenon following denosumab discontinuation may be compounded by the development of secondary conditions, which can result in suboptimal response to antiresorptive osteoporosis medications.

Effect of 2 Years of Monthly Calcifediol Administration in Postmenopausal Women with Vitamin D Insufficiency.

BACKGROUND: We assessed the long-term (24 months) efficacy and safety of monthly calcifediol (0.266 mg) in the correction and maintenance of total 25(OH)D levels in postmenopausal women with basal values <30 ng/mL. METHODS: We initially enrolled 45 consecutive patients during the period September 2019-September 2020. After an initial visit, patients were instructed to return at 3, 6, 9, 12 and 24 months for measuring serum total 25(OH)D, ionised calcium, creatinine and isoenzyme of alkaline phosphatase (bALP). Here, we report only the per-protocol analysis, because the COVID-19 pandemic precluded adherence to the scheduled visits for some patients. RESULTS: The patients' mean age was 62.4 ± 9.0 years. Mean basal 25(OH)D levels were 20.5 ± 5.3 ng/mL. There was a continuous increase of mean 25(OH)D values (p for trend < 0.001). However, mean values at month 24 (36.7 ± 15.9) were not significantly different in respect to values at month 12 (41.2 ± 11.18). At 24 months, only 1 out 19 patients had a value <20 ng/mL. There was a significant decrease with time of mean values of bALP (p < 0.0216), with no significant changes between 12 and 24 months. No significant changes were observed as far as ionised calcium or creatinine were concerned. CONCLUSIONS: The long-term administration of calcifediol maintains stable and sustained 25(OH)D concentrations, with no safety concerns.

The effect of parathyroidectomy on chronic constipation in patients affected by primary hyperparathyroidism.

Primary hyperparathyroidism (PHPT) is usually associated with chronic constipation; however, its prevalence is not defined by standardized criteria. The aim of the study was to evaluate both the prevalence of chronic constipation, defined by the standardized Rome diagnostic criteria III (Rome III) in PHPT, and the effect of parathyroidectomy (PTx). Fifty postmenopausal PHPT patients and 50 sex- and age-matched controls were studied. Each patient underwent mineral metabolism biochemical evaluation and completed a questionnaire and a 2-week diary card about bowel habits. PHPT patients were reevaluated after 6 months. According to Rome III, 40 % of PHPT patients had chronic constipation compared with 12 % of controls (p = 0.0002). The only difference between constipated PHPT patients (group A, n = 20) and those without constipation (group B, n = 30) was higher mean PTH values (79.9 ± 18.7 ng/l vs. 65.4 ± 26.0 ng/l; p = 0.03), which predicted the presence of constipation (p = 0.004, OR 1.059, CI 1.011-1.059). Forty percent of PHPT patients had undergone PTx. In group A, constipation was resolved in 80 % of patients after PTx compared to none of the same group who had not undergone PTx (p = 0.0007). In group B, 17.6 % of patients who had not undergone PTx became, after 6 months, constipated. According to Rome III, a higher prevalence of chronic constipation in PHPT patients was observed compared with controls. PTH levels predicted constipation. A significant reduction of chronic constipation was reported following successful surgery.

ASu@MNPs-based electrochemical immunosensor for vitamin D3 serum samples analysis.

We report a new sensitive label-free electrochemical immunosensor to detect Vitamin D3 (25-OHD3) in untreated serum samples. To this aim, a graphite screen printed electrode (SPE) was modified using cysteamine (CYM) functionalized core-shell magnetic nanoparticles (Au@MNPs) then, the 25-OHD3 antibody (AbD) was immobilized via glutaraldehyde crosslinking. The several steps involved in the immunosensor development and 25-OHD3 analysis were monitored by using differential pulse voltammetry (DPV). The developed immunosensor showed a LOD of 2.4 ng mL-1 and a linear range between 7.4 and 70 ng mL-1. The effectiveness of the immunosensor in human serum analysis was assessed by comparing the results obtained with the chemiluminescence-immunoassay (CLIA) reference method. The high sensitivity and excellent agreement with the reference method suggest its potential use as a POCT to monitor hypovitaminosis 25-OHD levels.

Tumor-induced Osteomalacia: A Comprehensive Review.

Tumor-induced osteomalacia (TIO) is an ultrarare paraneoplastic syndrome due to overproduction of fibroblast growth factor 23 (FGF23), with profound effects on patient morbidity. TIO is an underdiagnosed disease, whose awareness should be increased among physicians for timely and proper management of patients. Symptoms reported by patients with TIO are usually nonspecific, thus rendering the diagnosis elusive, with an initial misdiagnosis rate of more than 95%. Biochemical features of TIO are represented by hypophosphatemia, increased or inappropriately normal levels of FGF23, and low to low normal circulating 1,25-dihydroxyvitamin D (1,25(OH)2D). Phosphaturic mesenchymal tumors are the pathological entities underlying TIO in most affected patients. There is now evidence that FN1-FGFR1 and FN1-FGF1 fusion genes are present in about half of tumors causing this paraneoplastic syndrome. Tumors causing TIO are small and grow slowly. They can occur in all parts of the body from head to toe with similar prevalence in soft tissue and bone. There are a number of functional and anatomical imaging techniques used for tumor localization; 68Ga DOTA-based technologies have better sensitivity. Surgery is the treatment of choice; several medical treatments are now available in case of inability to locate the tumor or in case of incomplete excision.

Impairment in muscle strength and its determinants in primary hyperparathyroidism: A study in postmenopausal women.

Neuromuscular impairment is described among the non-classical complications of primary hyperparathyroidism (PHPT). However, the extent of this complications and related mechanisms have not been fully addressed. The study aimed at assessing muscle strength and its main determinants in postmenopausal women with PHPT. We studied 48 postmenopausal women with PHPT (mean age 60.8 ± 5.6 SD years; BMI 25.6 ± 5.5 kg/m2) and 38 healthy postmenopausal women (mean age 58.6 ± 5.9; BMI 25.2 ± 3.5). In all subjects, the maximum voluntary contraction (MVC, Newton, N) was measured by Hand held Dynamometer (Kayser Italia srl, Livorno, Italy) and the lumbar spine, total hip, femoral neck, and non dominant distal one-third radius areal BMD (aBMD) by dual X-ray absorptiometry (DXA) (Hologic, Waltham, MA). Serum ionized calcium (Ca++), parathyroid hormone (PTH), phosphorus (P), and 25-hydroxyvitaminD [25(OH)D] levels were measured in both groups. A subgroup of 30 PHPT women agreed to participate to the follow-up sub-study and were re-assessed 24 months after parathyroidectomy (n = 15) or after baseline evaluation (n = 15). Patients with PHPT had significant lower MVC values compared to healthy women (p < 0.001). As expected, serum Ca++ and PTH levels were higher and P lower in PHPT compared to controls. We observed a significant association between MVC and total hip and one-third radius aBMD (R = 0.320 and 0.370, p < 0.05) and negative association with Ca++ (R = -0.340, p < 0.05) in the PHPT group; MVC was positively associated with one-third radius aBMD (R = 0.360, p < 0.05) and negatively with age, BMI and myostatin (R = -0.390, -0.340 and -0.450, p < 0.05) in the group of healthy women. The linear model using BMI, Ca++, P, 25(OH)D, PTH, myostatin, and aBMD as covariates showed that one-third radius aBMD was positively associated with MVC in PHPT patients (p < 0.02) and in healthy subjects (p < 0.001). Additionally, serum PTH and myostatin were negatively associated with MVC in healthy subjects (p < 0.03 and p < 0.01). The linear model showed that surgery was associated with an increase in MVC (p < 0.05) in PHPT patients after 24 months, all other variables being equal and by controlling for baseline values of MVC. Handgrip strength is significantly impaired in postmenopausal women with PHPT. Some common mechanisms influencing muscle function exist in PHPT and in healthy subjects; they are associated with the reduced aBMD at cortical sites. Hypercalcemia seems to be one of the main determinants of impairment in muscle strength in PHPT, while no role is played by myostatin.

Bone Marrow Adipose Tissue Is Increased in Postmenopausal Women With Postsurgical Hypoparathyroidism.

CONTEXT: Suppression of bone turnover, greater trabecular volume, and normal-high normal all-site bone mineral density (BMD) are hallmarks of postsurgical hypoparathyroidism (HypoPT). Impairment in the trabecular microarchitecture with possible higher risk of vertebral fractures (VF) in women with postmenopausal HypoPT has also been described. Currently, no data on bone marrow adipose tissue (BMAT) are available in HypoPT. OBJECTIVE: To assess BMAT by magnetic resonance imaging (MRI) and proton magnetic resonance spectroscopy (1H-MRS) in postmenopausal women with chronic postsurgical HypoPT. METHODS: This cross-sectional pilot study, conducted at an ambulatory referral center, included 29 postmenopausal women (mean age 66 ± 8.4 years) with postsurgical HypoPT and 31 healthy postmenopausal women (mean age 63 ± 8.5). Lumbar spine MRI was performed and BMAT was measured by applying PRESS sequences on the L3 body. Lumbar spine, femoral neck, and total hip BMD were measured by dual x-ray absorptiometry (DXA); site-matched spine trabecular bone score (TBS) was calculated by TBS iNsight (Medimaps, Switzerland); VF assessment was performed with lateral thoracic and lumbar spine DXA. RESULTS: Fat content (FC) and saturation level (SL%) were higher (P <.0001 and P <.001), while water content (W) was lower in HypoPT compared to controls (P <.0001). FC significantly correlated with years since menopause and body weight (P <.05) in HypoPT, while TBS negatively correlated with FC and SL% (P <.05) and positively with residual lipids (RL) and W (P <.05). CONCLUSION: We demonstrate for the first time that BMAT is increased in postmenopausal women with postsurgical hypoparathyroidism and negatively associated with trabecular microarchitecture.

Occipital bone and tumor-induced osteomalacia: a rare tumor site for an uncommon paraneoplastic syndrome.

INTRODUCTION: Tumor-induced osteomalacia (TIO) is an uncommon paraneoplastic syndrome due to the overproduction of fibroblast growth factor 23 (FGF23). It is predominantly caused by mesenchymal tumors and cured upon their complete removal. Non-surgical treatment is an alternative option but limited to specific clinical conditions. METHODS: We report a challenging case of TIO caused by a tumor involving the occipital bone. We also performed a literature review of TIO caused by tumors localized at this site, focusing on clinical findings, treatment, and outcomes. RESULTS: The patient, a 62-year-old male, presented with a long-lasting history of progressive weakness. Biochemical evaluation revealed severe hypophosphatemia due to low renal tubular reabsorption of phosphate with raised intact FGF23 values. A 68 Ga-DOTATATE PET/TC imaging showed a suspicious lesion located in the left occipital bone that MRI and selective venous catheterization confirmed to be the cause of TIO. Stereotactic gamma knife radiosurgery was carried out, but unfortunately, the patient died of acute respiratory failure. To date, only seven additional cases of TIO have been associated to tumors located in the occipital bone. Furthermore, the tumor involved the left side of the occipital bone in all these patients. CONCLUSION: The occipital region is a difficult area to access so a multidisciplinary approach for their treatment is required. If anatomical differences could be the basis for the predilection of the left side of the occipital bone, it remains to be clarified.

The Mutual Interplay between Bone, Glucose and Lipid Metabolism: The Role of Vitamin D and PTH.

BACKGROUND: We sought to investigate the mutual interplay between bone, glucose and lipid metabolism in a wide cohort of community-based subjects. METHODS: We studied 1240 blood donors (F/M ratio 1/3.2, mean age 41.9 ± 11.7 SD). Serum ionized (Ca++), magnesium (Mg++), 25-hydroxy-vitamin D [25(OH)D], PTH-1-84, 1,25-dihydroxyvitamin D [1,25(OH)2D], total cholesterol (C), HDL-C, triglycerides and glucose were measured and LDL-C levels were calculated in all subjects. RESULTS: 25(OH)D negatively correlated with BMI (R = -0.11), PTH (R = -0.16) (p < 0.0001), total C (R = -0.06, p < 0.05) and triglycerides (R = -0.13, p < 0.0001) and positively with 1,25(OH)2D (R = 0.12) and creatinine (R = 0.17) (p < 0.0001). Serum PTH positively correlated with total C (R = 0.08, p < 0.01), LDL-C (R = 0.1, p < 0.001), triglycerides (R = 0.09, p < 0.01) and glucose (R = 0.15, p < 0.0001) and negatively with HDL-C (R = -0.09, p < 0.01). The odds of showing abnormal serum triglycerides and HDL-C increased as 25(OH)D decreased (p < 0.0001 and p < 0.03) and PTH increased (p < 0.03 and p = 0.05), while the odds of showing abnormal LDL-C levels increased in association with elevated PTH (p < 0.01). CONCLUSION: Vitamin D, PTH, glucose and lipid metabolism are mutually influenced. Hypovitaminosis D predisposes toward worsening lipid profiles through the actions of PTH, while serum PTH levels per se associate with higher glucose and LDL-C levels.

Genetic aspects underlying the normocalcemic and hypercalcemic phenotypes of primary hyperparathyroidism.

PURPOSE: Hypercalcemic primary hyperparathyroidism (PHPT) is a common endocrine disorder that has been very well characterized. In contrast, many aspects of normocalcemic primary hyperparathyroidism (NPHPT) such as natural history, organ damage, and management are still matter of debate. In addition, both the pathophysiology and molecular basis of NPHPT are unclear. We investigated whether PHPT and NPHPT patient cohorts share the same pattern of genetic variation in genes known to be involved in calcium and/or bone metabolism. RESEARCH DESIGN AND METHODS: Genotyping for 9 single nucleotide polymorphisms (SNPs) was performed by Real-Time PCR (TaqMan assays) on 27 NPHPT and 31 PHPT patients evaluated in a tertiary referral Center. The data of both groups were compared with 54 in house-controls and 503 subjects from the 1000 Genomes Project. All groups were compared for allele/haplotype frequencies, on a single locus, two loci and multi-locus basis. RESULTS: The NPHPT group differed significantly at SNPs in OPG and ESR1. Also, the NPHPT cohort was peculiar for pairwise associations of genotypes and for the overrepresentation of unusual multilocus genotypes. CONCLUSIONS: Our NPHPT patient set harbored a definitely larger quota of genetic diversity than the other samples. Specific genotypes may help in defining subgroups of NPHPT patients which deserve ad hoc clinical and follow-up studies.

FGF23 functions and disease.

The main function of fibroblast growth factor 23 (FGF23) is the regulation of phosphate metabolism through its action on the sodium-dependent phosphate cotransporters in the proximal renal tubules. Additionally, FGF23 interacts with vitamin D and parathyroid hormone in a complex metabolic pathway whose detailed mechanisms are still not clear in human physiology and disease. More recently, research has also focused on the understanding of mechanisms of FGF23 action on organs and system other than the kidneys and bone, as well as on its interaction with other metabolic pathways. Collectively, the new evidence are successfully used for the clinical evaluation and management of FGF23-related disorders, for which new therapies with many potential applications are now available.

Osteomalacia and Vitamin D Status: A Clinical Update 2020.

Historically, rickets and osteomalacia have been synonymous with vitamin D deficiency dating back to the 17th century. The term osteomalacia, which literally means soft bone, was traditionally applied to characteristic radiologically or histologically documented skeletal disease and not just to clinical or biochemical abnormalities. Osteomalacia results from impaired mineralization of bone that can manifest in several types, which differ from one another by the relationships of osteoid (ie, unmineralized bone matrix) thickness both with osteoid surface and mineral apposition rate. Osteomalacia related to vitamin D deficiency evolves in three stages. The initial stage is characterized by normal serum levels of calcium and phosphate and elevated alkaline phosphatase, PTH, and 1,25-dihydroxyvitamin D [1,25(OH)2D]-the latter a consequence of increased PTH. In the second stage, serum calcium and often phosphate levels usually decline, and both serum PTH and alkaline phosphatase values increase further. However, serum 1,25(OH)2D returns to normal or low values depending on the concentration of its substrate, 25-hydroxyvitamin D (25OHD; the best available index of vitamin D nutrition) and the degree of PTH elevation. In the final stage, hypocalcemia and hypophosphatemia are invariably low with further exacerbation of secondary hyperparathyroidism. The exact,or even an approximate, prevalence of osteomalacia caused by vitamin D deficiency is difficult to estimate, most likely it is underrecognized or misdiagnosed as osteoporosis. Signs and symptoms include diffuse bone, muscle weakness, and characteristic fracture pattern, often referred to as pseudofractures, involving ribs, scapulae, pubic rami, proximal femurs, and codfish-type vertebrae. The goal of therapy of vitamin D-deficiency osteomalacia is to alleviate symptoms, promote fracture healing, restore bone strength, and improve quality of life while correcting biochemical abnormalities. There is a need for better understanding of the epidemiology of osteomalacia. Simplified tools validated by concurrent bone histology should be developed to help clinicians promptly diagnose osteomalacia. © 2020 The Authors. JBMR Plus published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research.