Teriparatide and fracture healing in cortical bone

Modulation of 25(OH) vitamin D3 level by Imatinib mesylate in patients with chronic myelogenous leukaemia: The role of uptake and efflux transporters

Background

Objective

Methods

Results

Conclusions

[Nutrient Status of Vitamin D among Cancer Patients]

BACKGROUND

There is a certain correlation between vitamin nutritional status and cancer patients. Studies have shown that vitamin deficiency increases the risk of cancer. The purpose of this study is to understand the vitamin D nutritional status of cancer patients and to provide scientific basis for further nutritional intervention.

METHODS

Cancer patients who visited Shandong Cancer Hospital from July 2017 to June 2019 were included in this retrospective study. Serum 25-hydroxyvitamin D [25(OH)D] concentrations were measured. Univariate analysis and multiple linear regression analysis were carried out using SPSS 20.0.

RESULTS

A total of 2,487 cancer patients were evaluable for this analysis. Mean 25(OH)D concentration was (12.70±6.82) ng/mL; the prevalence of vitamin D deficiency [25(OH)D concentration less than 20.00 ng/mL] was of 92.20%. In univariate analysis, age, body mass index (BMI), season and types of cancer were associated with 25(OH)D concentrations. In the multivariate analysis, BMI (β=0.71), age (β=-0.56), season (β=-0.99 for winter; β=-0.76 for autumn vs summer) and types of cancer (β=-1.17 for lung cancer; β=-1.45 for esophageal-gastric cancer; β=-1.05 for colorectal cancer vs other types of cancer) were independently and significantly associated with 25(OH)D levels (P<0.05).

CONCLUSIONS

Vitamin D deficiency was highly prevalent among cancer patients. Age, BMI, season and types of cancer may be associated with 25(OH)D levels, which indicate that monitoring of vitamin D level for cancer survivor should be taken into account.

The effectiveness and safety of parathyroid hormone in fracture healing: A meta-analysis

The very large economic and social burdens of fracture-related complications make rapid fracture healing a major public health goal. The role of parathyroid hormone (PTH) in treating osteoporosis is generally accepted, but the effect of PTH on fracture healing is controversial. This meta-analysis was designed to investigate the efficacy and safety of PTH in fracture healing. The EMBASE, PubMed, and Cochrane Library databases were systematically searched from the inception dates to April 26, 2018. The primary randomized clinical trials comparing PTH treatment for fracture healing with placebo or no treatment were identified. We did not gain additional information by contacting the authors of the primary studies. Two reviewers independently extracted the data and evaluated study quality. This meta-analysis was executed to determine the odds ratio, mean difference, standardized mean difference, and 95% confidence intervals with random-effects models. In total, 8 randomized trials including 524 patients met the inclusion criteria. There were significant differences in fracture healing time, pain relief and function improvement. There were no significant differences in the fracture healing rate or adverse events, including light-headedness, hypercalcemia, nausea, sweating and headache, except for slight bruising at the injection site. We determined that the effectiveness and safety of PTH in fracture healing is reasonably well established and credible.

A case of severe, irreversible hypocalcemia after one dose of pamidronate administered for hypercalcemia of malignancy

This is a case report of a patient who developed severe, irreversible hypocalcemia after receiving one dose of pamidronate 90 mg for hypercalcemia of malignancy. Hypocalcemia is a known risk of bisphosphonate treatments, but the incidence of severe hypocalcemia is rare, and the risk factors are well established. However, in the treatment of hypercalcemia of malignancy, the treatment objective is to reduce the elevated serum calcium level, and the bisphosphonate is usually given as one time dose only. The potential for developing severe hypocalcemia may not be considered a significant concern in this setting compared to the setting of the treatment of bone metastasis, where the baseline serum calcium level is not elevated and the bisphosphonate is administered at a regular interval of every three to four weeks. Furthermore, there is unawareness of prevalence of vitamin D deficiency in cancer patients, especially in those with advanced cancer, which may lead to inadvertent, severe hypocalcemia from bisphosphonate treatment. The objective of this case report is to bring awareness to the risk of severe hypocalcemia in patients with hypercalcemia of malignancy and the high prevalence of unrecognized vitamin D deficiency in cancer patients.

Effectiveness of Teriparatide on Fracture Healing: A Systematic Review and Meta-Analysis

Purpose

Nowadays, the efficacy of teriparatide in treating osteoporosis was widely accepted, but the discussion about using teriparatide to enhance fracture healing hasn’t come to an agreement. This meta-analysis was conducted to evaluate the effectiveness of teriparatide for fracture healing.

Methods

We searched PubMed, the Cochrane Library, and Embase in August 2016 for randomized controlled trials (RCTs) which concerned the treatment of teriparatide for fracture healing.

Results

Finally, a total of 380 patients were randomly assigned in the 5 trials included in this meta-analysis. There was a significant effectiveness with regards to function improvement in patients following fracture, however, there was no significant effectiveness with regards to time of radiographic fracture healing, fracture healing rate and reduction in pain.

Conclusions

This analysis showed that administration of teriparatide following fracture lacked the effectiveness for fracture healing. Moreover, teriparatide administration had no apparent adverse effects. These results should be interpreted with caution because of some clear limitations. If we want to confirm whether teriparatide improves fracture healing, more high-quality randomized controlled trials are needed.

[Medication and bone metabolism: Clinical importance for fracture treatment]

INTRODUCTION

The improvement and acceleration of fracture healing has been a component of medical practice since fractures have been treated. The aim is not only to fulfill the basic principles of fracture healing, such as reduction, retention, soft tissue coverage and infection prevention but also to reduce negative influences on fracture healing and promote positive factors. Nicotine, alcohol, diabetes and malnutrition can negatively affect fracture healing and should be appropriately controlled during fracture treatment; however, it is far more difficult to develop medicinal treatment strategies that lead to improvement and acceleration of fracture healing.

AIM

This article provides an overview of pharmacological factors influencing fracture healing. In addition, substances frequently used in clinical practice will be evaluated in terms of the effects on fracture healing processes.

MATERIAL AND METHODS

An extensive literature search was conducted in PubMed based on thematic keywords. The selection of studies and scientific publications focused mainly on results from clinical trials in order to provide practically relevant information.

RESULTS

In this context, preclinical studies have identified several drugs that lead to the acceleration of fracture healing; however, only a very limited number of clinical trials have confirmed this positive effect. Most of these studies dealt with drugs developed for the treatment of osteoporosis, as osteoporotic fractures are common and a positive or negative influence of such drugs are of particular interest in this field. In the field of osteoporosis medication a certain degree of positive effect of parathyroid hormone 1-34 (PTH) on fracture healing has been shown in clinical trials. For other osteoporosis medications no negative influence on fracture healing in clinical settings has been reported; however, there seems to be a positive effect in terms of better implant fixation for patients receiving oral bisphosphonate therapy.

DISCUSSION

Systemic medication to improve fracture healing will not be part of the clinical routine in the foreseeable future as the available data for already approved drugs and drugs under development do not currently justify routine administration. However, the currently known data should encourage the potential of known medications to be completely exhausted in fracture healing studies as well as novel therapy options in the sense of positive effects on fracture healing in order to improve patient care.

Does Teriparatide Improve Femoral Neck Fracture Healing: Results From A Randomized Placebo-controlled Trial

BACKGROUND

There is a medical need for therapies that improve hip fracture healing. Teriparatide (Forteo(®)/ Forsteo(®), recombinant human parathyroid hormone) is a bone anabolic drug that is approved for treatment of osteoporosis and glucocorticoid-induced osteoporosis in men and postmenopausal women at high fracture risk. Preclinical and preliminary clinical data also suggest that teriparatide may enhance bone healing.

QUESTIONS/PURPOSES

We wished to test the hypotheses that treatment with teriparatide versus placebo would improve femoral neck fracture healing after internal fixation as measured by (1) frequency of revision surgery, (2) radiographic fracture healing, and (3) other outcomes including pain control, gait speed, and safety.

METHODS

We initiated two separate, but identically designed, clinical trials to meet FDA requirements to provide substantial evidence to support approval of a new indication. The two prospective, randomized double-blind, placebo-controlled Phase III studies were designed to evaluate the effect of subcutaneous teriparatide (20 μg/day) for 6 months versus placebo on fracture healing at 24 months. The trials were conducted concurrently with a planned enrollment of 1220 patients per trial. However, enrollment was stopped owing to very slow patient accrual, and an a priori decision was made to pool the results of those studies for statistical analyses before study completion; pooling was specified in both protocols. Randomization was stratified by fixation (sliding hip screw or multiple cancellous screws) and fracture type (displaced or nondisplaced). An independent Central Adjudication Committee reviewed revision surgical procedures and radiographs. A total of 159 patients were randomized in the two trials (81 placebo, 78 teriparatide). The combined program had very low power to detect the originally expected treatment effect but had approximately 80% power to detect a larger difference of 12% between treatment groups for risk of revision surgery.

RESULTS

The proportion of patients undergoing revision surgery at 12 months was 14% (11 of 81) in the placebo group versus 17% (13 of 78) in the teriparatide group. Central Adjudication Committee review excluded two of these patients treated with placebo from the primary analysis. After exclusions, the proportion of patients who did not undergo revision surgery at 12 months (primary endpoint) was not different between the study and placebo groups, at 88% in the placebo group (90% CI, 0.79-0.93) versus 84% in the teriparatide group (90% CI, 0.75-0.90; p = 0.743). There also were no differences between groups in the proportion of patients achieving radiographic fracture healing at 12 months (75% [61 of 81] placebo versus 73% [57 of 78] teriparatide; odds ratio, 0.89; 90% CI, 0.46-1.72; p = 0.692) or in measures of pain control (such as pain during ambulation, 92% [55 of 62] placebo versus 91% [52 of 57] teriparatide; odds ratio, 0.91; 90% CI, 0.25-3.37; p = 0.681). The frequency of patients reporting adverse events was 49% [40 of 81] in the placebo group versus 45% [35 of 78] in the teriparatide group (p = 0.634) during the 6-month treatment period.

CONCLUSIONS

The small sample size limited this study's power to detect potential differences, and the results are exploratory. With the patients available, teriparatide did not decrease the risk of revision surgery, improve radiographic signs of fracture healing, or decrease pain compared with the placebo. The adverse event data observed were consistent with the teriparatide safety profile. Functional and health outcome data from the studies may help improve our understanding of patients recovering from femoral neck fractures. Further large controlled studies are required to determine the effect of teriparatide on fracture healing.

LEVEL OF EVIDENCE

Level II, prospective study.

Low 25-hydroxyvitamin D levels in people with a solid tumor cancer diagnosis: the tip of the iceberg?

PURPOSE

Low serum 25-hydroxyvitamin D [25(OH)D] levels have been linked to both cancer incidence and poor prognosis. The frequency of 25(OH)D tests and clinical factors associated with low levels in cancer patients are unknown.

PATIENTS AND METHODS

Electronic medical records from 2006 to 2007 of 39,252 adult solid tumor patients were reviewed. Data included demographics, cancer sites (primary and metastatic), and first serum 25(OH)D level during the study period. Laboratory data, comorbidities, selected medications, and anticancer treatment within the prior 2 months were recorded. Data were compared between (1) those tested and not tested and (2) 25(OH)D levels≤10 ng/ml (deficient), 11-30 ng/ml (insufficient), and ≥31 ng/ml (sufficient). Stepwise logistic regression identified independent predictors of low serum 25(OH)D levels.

RESULTS

The cohort was 86% Caucasian and 48% female with a mean age of 63±14 years (mean±SD). The most prevalent cancer was breast (19%). In total, 2,098 (5%) had a 25(OH)D test. Of those tested, 133 (6%) had levels≤10 ng/ml and 1,311 (62%) 11-30 ng/ml. Tests were more frequent in females and in those with breast, skin, and thyroid cancers (P<0.001). Low 25(OH)D levels were associated (in univariable analyses) with male gender, non-Caucasian race, gastrointestinal tumor primary sites, metastatic disease, benign liver disease, low serum albumin, and elevated liver enzymes. Significant factors in multivariable models for 25(OH)D levels≤10 and ≤30 ng/ml included non-Caucasian race, primary cancer site, and test calendar month. Vitamin D supplements and recent antineoplastic medication were associated with sufficient levels.

CONCLUSIONS

Low (deficient or insufficient) 25(OH)D serum levels were highly prevalent in people with solid tumors. Vitamin D tests were infrequent and paradoxically less often done in high-risk groups. Tests were more frequent in females and in those with breast, skin, and thyroid cancers. Further research should examine role of routine 25(OH)D tests, the clinical consequences of low levels, and therapeutic supplementation in people with cancer.

Successful treatment of nonunion with teriparatide after failed ankle arthrodesis for Charcot arthropathy

We describe a case of successful treatment to nonunion after multiple arthrodesis operations for Charcot arthropathy with teriparatide. We describe the case of a 25-year-old woman with severe Type I diabetes mellitus that resulted in nonunion after multiple arthrodesis operations for Charcot arthropathy. The woman sustained a femoral shaft fracture for which she underwent surgery with intramedullary nail fixation. Immediately after surgery, an empiric course of teriparatide was initiated. Femoral shaft fracture healing was observed after 2 weeks, and the woman was able to walk 12 weeks after the surgery, at which point plain film and computed tomography images revealed complete union of the ankle.

Teriparatide, a nonsurgical solution for femoral nonunion? A report of three cases

We medicated teriparatide in three patients, who had a nonunion of the femur even after the initial surgical intervention. Teriparatide was administered for 3-9 months after a diagnosis of nonunion. A successful union was obtained in all three patients without further surgical intervention, and no adverse events related to the use of teriparatide were observed. Our report showed that teriparatide could be an alternative to surgical intervention in nonunion of the femur.

Serum 25-hydroxyvitamin D levels are associated with prognosis in hematological malignancies

It has been proposed that Vitamin D has a significant influence on disease progression in malignancy. This study aims to investigate whether serum levels of 25-hydroxyvitamin D [25(OH)D] are associated with prognosis in patients with hematological malignancies. This study is based on 105 patients with hematological disease (acute and chronic leukemias, myelodysplastic syndromes, monoclonal gammapathies, and chronic lymphoid disorders), seen over a 6-months period. 25(OH)D deficiency (<20 ng/ml) appeared very common and an inverse relationship was observed between 25(OH)D levels and the response to therapy: lower levels being related to poorer response. In acute leukemias, a significant difference was noted between patients with long-term disease-free survival in those tested at diagnosis (P=0·001) or in those tested at the time of relapse (P=0·05). Similarly in patients with Philadelphia-positive leukemias, there was a correlation between molecular response and levels of 25(OH)D (P=0·01). Previously identified factors, such as age, season, gender, or nutritional index, were not related to circulating 25(OH)D levels. Lower levels of circulating 25(OH)D appeared related to a progressive stage of the disease and poor response to therapy, and, therefore, to the aggressiveness of the disease. It is a potential marker of prognosis in patients with leukemia.

Solar UV doses of adult Americans and vitamin D(3) production

BACKGROUND

Sunlight contains UV radiation that affects human health in both detrimental (skin cancers) and beneficial (vitamin D(3)) ways. An evaluation of the vitamin D status of adult Americans (22-40, 41-59, 60+ yr) show many have deficient or insufficient serum levels of 25-hydroxyvitamin D, indicating they are not getting enough from dietary sources or sunlight. Those findings are in conflict with calculated values from the American Academy of Dermatology who insist people make "ample" vitamin D(3) (≥1,000 IU/day) from their "casual," or everyday, outdoor UV exposures even if they use sunscreens with sun protection factor 15.

OBJECTIVE

We investigated this situation using the everyday outdoor UV doses of indoor-working adult Americans (∼7,000) in the north (45°N) and south (35°N) to calculate how much vitamin D(3) they produce each season with and without vacationing.

RESULTS

Only during the summer can skin type II Caucasian adults (21-59 yr) meet their minimum (600 IU/day) vitamin D(3) needs from everyday exposures, but only if they do not wear professional clothes or sunscreens (except beach vacations).

METHOD

To do vitamin D(3) calculations properly, we used action spectrum and geometric conversion factors, not previously incorporated into other calculations.

CONCLUSIONS

Most adult Americans do not go outside enough to meet their minimum or optimum (≥1,200 IU/day) vitamin D(3) needs all year. The darker skin types (III-VI) and the oldest people (>59 yr) are at the highest risk for not making enough vitamin D(3) during the year from everyday outdoor exposures even with a 2-3 week summer vacation.

Prevalence of serum vitamin D deficiency and insufficiency in cancer: Review of the epidemiological literature

Vitamin D deficiency has been found to be associated with a variety of cancers, including prostate, multiple myeloma, colorectal and breast cancer. Several studies have shown vitamin D levels to have an inverse relation with cancer mortality, while others have considered it a potential risk factor. Vitamin D is believed to influence cancer prevalence, risk and survival; hence the need to assess vitamin D levels in cancer. Although numerous studies have been conducted to demonstrate vitamin D deficiency as a risk factor for cancer, relatively few have studied its prevalence. Moreover, studies estimating prevalence differ from each other, with respect to study population, sample size, study design, definition of vitamin D deficiency used and method of vitamin D assessment (with most studies limited to one particular type of cancer with relatively small sample sizes). Therefore, we qualitatively reviewed the epidemiological evidence in the oncology literature on the prevalence of vitamin D deficiency and insufficiency as measured by serum vitamin D concentrations.

Vitamin D status among long-term survivors of hematopoietic cell transplantation

Little is known about serum vitamin D levels following hematopoietic cell transplantation (HCT). Patients are instructed to avoid sun exposure due to an increased risk of skin cancers. Altered gastrointestinal absorptive capacity as a result of GVHD, bile acid or pancreatic enzyme insufficiency, or bacterial overgrowth may lead to difficulty absorbing the fat soluble vitamin D. This study was undertaken to determine the prevalence of serum 25-hydroxyvitamin D (25(OH)D) deficiency, and factors associated with 25(OH)D deficiency, among children and adults who were at least one year following HCT. A total of 95 participants (54 males, 41 females) completed a questionnaire on usual diet and lifestyle, and provided a blood sample for 25(OH)D determinations between November 2008 and July 2009. The majority of participants had serum 25(OH)D levels ≥75 nmol/L (n=62, 65%), 23 had insufficient levels (50–75 nmol/L), and 10 participants were deficient (<50 nmol/L). The majority of participants reported regular vitamin D supplement use (n=58, 61%). Prednisone use was significantly inversely associated with serum 25(OH)D concentrations. Total vitamin D intake was the strongest single predictor of 25(OH)D concentrations. These findings suggest that 400–600 IU vitamin D/day appear to be required to achieve optimal serum 25(OH)D concentrations following HCT.

Successful treatment of sternal fracture nonunion with teriparatide

SUMMARY

Fractures have a significant impact on the quality of life for the patient in addition to an enormous indirect cost in lost productivity for our economy. While majority of fractures heal uneventfully, some fail to heal even after many months resulting in nonunion.

INTRODUCTION

Sternal nonunions, although rare, are particularly onerous for the patient given the magnitude of impact on quality of life.

METHODS

Current treatment for fracture nonunions emphasizes various approaches to surgical fixation in addition to bone grafting. These treatments are aggressive and have a variety of drawbacks, rendering them suboptimal as a therapeutic approach.

CONCLUSION

Based on the success of teriparatide in animal studies to accelerate fracture healing, there is growing interest in using this drug in humans for the same purpose. We report a case of what we believe to be the first successful use of teriparatide in the healing of a sternal nonunion fracture.

Vitamin D deficiency and insufficiency among patients with prostate cancer

OBJECTIVE

To assess the frequency of vitamin D deficiency among men with prostate cancer, as considerable epidemiological, in vitro, in vivo and clinical data support an association between vitamin D deficiency and prostate cancer outcome.

PATIENTS, SUBJECTS AND METHODS

The study included 120 ambulatory men with recurrent prostate cancer and 50 with clinically localized prostate cancer who were evaluated and serum samples assayed for 25-OH vitamin D levels. Then 100 controls (both sexes), matched for age and season of serum sample, were chosen from a prospective serum banking protocol. The relationship between age, body mass index, disease stage, Eastern Cooperative Oncology Group performance status, season and previous therapy on vitamin D status were evaluated using univariate and multivariate analyses.

RESULTS

The mean 25-OH vitamin D level was 25.9 ng/mL in those with recurrent disease, 27.5 ng/mL in men with clinically localized prostate cancer and 24.5 ng/mL in controls. The frequency of vitamin D deficiency (<20 ng/mL) and insufficiency (20-31 ng/mL) was 40% and 32% in men with recurrent prostate; 28% had vitamin D levels that were normal (32-100 ng/mL). Among men with localized prostate cancer, 18% were deficient, 50% were insufficient and 32% were normal. Among controls, 31% were deficient, 40% were insufficient and 29% were normal. Metastatic disease (P = 0.005) and season of blood sampling (winter/spring; P = 0.01) were associated with vitamin D deficiency in patients with prostate cancer, while age, race, performance status and body mass index were not.

CONCLUSIONS

Vitamin D deficiency and insufficiency were common among men with prostate cancer and apparently normal controls in the western New York region.

Solar ultraviolet-B irradiance and vitamin D may reduce the risk of septicemia

The primary features of the epidemiology of septicemia in the United States include highest rates in winter and the Northeast, lowest in fall and in the West; higher rates among African Americans than white Americans; a rapid increase in incidence with age; comorbidity with several chronic and infectious diseases; and a rapid increase in incidence rate starting in the early 1980s. This article reviews the literature on the epidemiology of septicemia in the United States, along with the roles of solar ultraviolet-B (UVB) and vitamin D3 related to the more important features. Solar UVB doses in summer are highest in the Southwest and lowest in the Northeast. Serum 25-hydroxyvitamin D [25(OH)D] levels are highest in summer, lowest in winter. African Americans have much lower 25(OH)D levels than those of white Americans. Serum 25(OH)D levels decline rapidly with advancing age. The risk of diseases comorbid with septicemia are generally inversely correlated with serum 25(OH)D levels. Sun-avoidance messages may have led to lower population levels of 25(OH)D, although prevalence of antibiotic-resistant bacteria may have increased. Previous reports have shown that 1,25-dihydroxyvitamin D upregulates human cathelicidin, LL-37, which has antimicrobial as well as antiendotoxin activity. The general agreement between the epidemiology of septicemia in the United States and the variations of solar UVB and the effects of vitamin D supports the hypothesis that both play important roles in reducing the risk of septicemia. Further study is warranted to evaluate this hypothesis.

Frequency of Combined Deficiencies of Vitamin D and Holotranscobalamin in Cancer Patients

Vitamin D and holotranscobalamin (HTCII) deficiencies have been seen to demonstrate an association with various types of cancers. The objective of this study is to determine the frequency of vitamin D and HTCII deficiency in cancer patients. Our study investigated vitamin D, total B12, and HTCII levels in 70 cancer patients. Vitamin D status was measured as serum 25-hydroxyvitamin D [25(OH)D, Nichols Advantage assay], and serum B12 was measured as both total B12 and as the metabolically active HTCII (Immulite B12 assay followed by glass adsorption). Insufficiency of serum 25(OH)D levels for this study is defined based on differing literature standards of insufficiency and was selected to be either <50 or <75 nmol/l. When 25(OH)D insufficiency is defined as serum level of <75 nmol/l, 43 of 60 (72%) of cancer patients were found to be insufficient. At the lower definition of insufficiency, <50 nmol/l, 24 of 60 patients (40%) were insufficient. Of 52 patients, only 3 (6%) were found to have insufficient serum levels of total B12 (normal = >300 pg/ml), whereas 17 of 52 (34%) were found to be HTCII insufficient (normal = >69 pg/ml). Of these 17 patients, 14 (84.4%) had normal total B12 levels. Low serum levels of 25(OH)D strongly correlated with low serum HTCII. All 12 HTCII-deficient patients were vitamin D insufficient at the <75-nmol/l standard. Six of 12 HTCII-deficient patients (50%) were vitamin D deficient at the <50-nmol/l cutoff. The standard measurement of total serum B12 alone is inadequate for identifying patients with insufficient levels of metabolically active B12. Deficiency of vitamin D (72%) and HTCII (34%) is prevalent among newly diagnosed patients with cancer and could play a role in cancer development and host response to tumor and therapy. Possible explanations for combined HTCII and 25(OH)D deficiencies include patient age, presence of atrophic gastritis, and lack of sun exposure.

Bisphosphonate-induced hypocalcemia: report of 3 cases and review of literature

OBJECTIVE

To report 3 cases of bisphosphonate-induced hypocalcemia and review the relevant literature.

METHODS

We present the clinical and laboratory findings in 3 cases of bisphosphonate-induced hypocalcemia, and discuss the pathophysiologic mechanisms and the pertinent literature.

RESULTS

In our first patient (case 1), symptomatic hypocalcemia developed after intravenous administration of pamidronate for management of multiple myeloma. He had vitamin D insufficiency and impaired renal function at the time of pamidronate therapy. Our second patient (case 2) presented with symptomatic hypocalcemia 12 weeks after initiation of alendronate therapy for osteoporosis. Her serum 25-hydroxyvitamin D level was low (3 ng/mL), attributable to a combination of poor vitamin D intake, limited exposure to sunlight, use of phenytoin, and previous intestinal resections. In our third patient (case 3), hypocalcemia developed on 2 different occasions, each episode occurring after intravenous administration of pamidronate for hypercalcemia of malignancy. All 3 patients had underlying conditions that impaired the homeostatic response to bisphosphonates and contributed to the severe hypocalcemia. Review of published reports on symptomatic bisphosphonate-induced hypocalcemia disclosed that hypocalcemia develops in patients with unrecognized hypoparathyroidism, impaired renal function, or vitamin D deficiency. Overall, the rate of the development of hypocalcemia was related to the potency of the bisphosphonate administered.

CONCLUSION

The increasing use of bisphosphonates and the introduction of more potent agents impose a considerable risk for bisphosphonate-induced hypocalcemia in a substantial number of patients. Greater awareness of this complication, a better understanding of the underlying mechanisms, and proper assessment of patients in whom bisphosphonate therapy is contemplated should reduce the frequency of occurrence of this potentially life-threatening complication.

Vitamin D deficiency enhances the growth of MC-26 colon cancer xenografts in Balb/c mice

Vitamin D deficiency has been associated with increased risk of colon cancer in epidemiologic and prospective clinical studies. In vitro and in vivo studies demonstrated that 1,25-dihydroxycholecalciferol [1,25(OH)2D3] and its analogs inhibit colon cancer cell proliferation. Few studies have evaluated the effect of vitamin D deficiency on the development and growth of colon cancer. To assess the antiproliferative effects of 25-hydroxyvitamin D [25(OH)D] and 1,25(OH)2D3 in vitro, we cultured MC-26 (a colon cancer cell line) in the presence of 25(OH)D3 and 1,25(OH)2D3 and performed [3H]thymidine incorporation. The proliferation of MC-26 was significantly inhibited by both 25(OH)D3 and 1,25(OH)2D3. To determine the effect of vitamin D deficiency on colon cancer proliferation, Balb/c mice were rendered vitamin D deficient by feeding them a vitamin D-deficient diet for 3 mo. A group of vitamin D-sufficient mice was given the same diet with supplemental vitamin D. The mice were injected with MC-26 colon cancer cells and the tumors were measured daily for 20 d. Vitamin D-sufficient mice had 40% smaller tumors than vitamin D-deficient mice. The tumors were evaluated for mRNA expression of the vitamin D receptor (VDR) and 25-hydroxvitamin D-1alpha-hydroxylase (1alpha-OHase) by quantitative RT-PCR. The expression of the mRNA for the VDR and the 1alpha-OHase was 37- and 6-fold higher, respectively, in the vitamin D-sufficient mice compared with the vitamin D-deficient mice. We conclude that vitamin D deficiency enhances the growth of colon cancer in mice. The tumor expression of VDR and 1alpha-OHase indicates possible autocrine/paracrine cell growth regulation by vitamin D.