Abnormalities of vitamin D and calcium metabolism after surgical treatment of morbid obesity: a study of 136 patients

Dynamic Evaluation of Vitamin D Metabolism in Post-Bariatric Patients

BACKGROUND

findings from the previously conducted studies indicate altered regulatory mechanisms of calcium and vitamin D metabolism in obese patients and a role for bariatric surgery in regulating vitamin D metabolism; however, the available data is controversial and does not provide an adequate understanding of the subject.

METHODS

we evaluated serum parameters of vitamin D and mineral metabolism (vitamin D metabolites (25(OH)D3, 25(OH)D2, 1,25(OH)2D3, 3-epi-25(OH)D3, and 24,25(OH)2D3), vitamin D-binding protein (DBP), free 25(OH)D, fibroblast growth factor 23 (FGF-23), parathyroid hormone (PTH), total calcium, albumin, phosphorus, creatinine, magnesium) in 30 patients referred for bariatric surgery in comparison with 30 healthy volunteers of similar age, sex and baseline 25(OH)D3. Patients were also followed up with repeated laboratory assessments 3 months and 6 months after surgery. During the first 3 months, patients were prescribed high-dose cholecalciferol therapy (50,000 IU per week), with subsequent correction based on the results of the 3-month visit examination.

RESULTS

Preoperatively, patients with morbid obesity were characterized by a high prevalence of vitamin D deficiency (median 25(OH)D3 level 11.9 (6.8; 22.2) ng/mL), significantly lower levels of active vitamin D metabolite 1,25(OH)2D3 (20 (10; 37) vs. 39 (33; 50) pg/mL, p < 0.001), lower serum albumin-adjusted calcium levels (2.24 (2.20; 2.32) vs. 2.31 (2.25; 2.35) mmol/L, p = 0.009) and magnesium levels (0.79 (0.72; 0.82) vs. 0.82 (0.78; 0.85) mmol/L, p = 0.043) with simultaneous similar PTH levels (p = 0.912), and higher DBP levels (328 (288; 401) vs. 248 (217; 284) mg/L, p < 0.001). The 25(OH)D3 levels remained suboptimal (24.5 (14.7; 29.5) ng/mL at the 3-month visit and 17.9 (12.4; 21.0) ng/mL at the 6-month visit, p = 0.052) despite recommended high-dose cholecalciferol supplementation. Patients also demonstrated an increase in 1,25(OH)2D3 levels (38 (31; 52) pg/mL at the 3-month visit and 49 (29; 59) pg/mL at the 6-month visit, p < 0.001) without a change in PTH or calcium levels during the follow-up.

CONCLUSION

our results of a comprehensive laboratory evaluation of vitamin D status and mineral metabolism in patients undergoing bariatric surgery highlight the importance of improving current clinical guidelines, as well as careful monitoring and education of patients.

Sex Differences of Vitamin D Status across BMI Classes: An Observational Prospective Cohort Study

Growing evidence reported that vitamin D deficiency is a common finding in obesity. Vitamin D status also seems to be sex-related, although little is known regarding this association. Therefore, the aim of this study was to investigate the sex-related differences of serum 25OH vitamin D (25OHD) concentrations across body mass index (BMI) classes and, if there were any differences, whether they could be explained by sex-related differences in body composition. We enrolled 500 subjects (250 males, age 37.4 ± 11.8 years; 250 females, age 36.6 ± 11.8 years). Body composition was assessed by bioelectrical impedance analysis (BIA) phase-sensitive system. Serum 25OHD concentration was quantified by a direct, competitive chemiluminescence immunoassay. Vitamin D deficiency was defined as a serum 25OHD concentrations < 20 ng/mL (50 nmol/L). Stratifying the sample population according to sex and BMI categories, 25OHD concentrations were significantly higher in males compared to females in all BMI classes and decreased along with the increase of BMI values. Females with vitamin D deficiency had higher fat mass (FM) % compared to males with vitamin D deficiency. The 25OHD concentrations inversely correlated with FM % in both sexes. In a multiple regression analysis model, sex, FM %, and BMI were predictive factors of 25OHD concentration. In conclusion, our study suggests that 25OHD concentrations were lower in females than males across all BMI categories. Given the tight correlation between 25OHD concentrations and FM %, it can be hypothesized that the lower 25OHD concentrations in females than males can be explained by the fact that females have a higher amount of fat than males.

IMPACT OF DEFICIENT NUTRITION IN BONE MASS AFTER BARIATRIC SURGERY

Background:

Essential nutrients are considered for the prevention of the bone loss that occurs after bariatric surgery.

Aim:

Evaluate nutrients involved in bone metabolism, and relate to serum concentrations of calcium, vitamin D, and parathyroid hormone, and the use of supplements and sun exposure on the bone mass of patients who had undergone gastric bypass surgery.

Methods:

An observational study, with patients who had undergone the surgery 12 or more months previously, operated group (OG), compared to a control group (CG).

Results:

Were included 56 in OG and 27 in the CG. The mean age was 36.4±8.5 years. The individuals in the OG, compared to CG, consumed inadequate amounts of protein and daily calcium. The OG had a higher prevalence of low sun exposure, lower levels of 25OH Vitamin D (21.3±10.9 vs. 32.1±11.8 ng/dl), and increased serum levels of parathyroid hormone (68.1±32.9 vs. 39.9±11.9 pg/ml, p<0.001). Secondary hyperparathyroidism was present only in the OG (41.7%). The mean lumbar spine bone mineral density was lower in the OG. Four individuals from the OG had low bone mineral density for chronological age, and no one from the CG.

Conclusion:

The dietary components that affect bone mass in patients undergoing bariatric surgery were inadequate. The supplementation was insufficient and the sun exposure was low. These changes were accompanied by secondary hyperparathyroidism and a high prevalence of low bone mass in lumbar spine in these subjects.

Hypovitaminosis D in bariatric surgery: A systematic review of observational studies

BACKGROUND

Obesity is a public health problem that carries global and substantial social and economic burden. Relative to non-surgical interventions, bariatric surgery has the most substantial and lasting impact on weight loss. However, it leads to a number of nutritional deficiencies requiring long term supplementation.

OBJECTIVES

The aims of this paper are to review 25-hydroxyvitamin D [25(OH)D] status pre and post bariatric surgery, describe the dose response of vitamin D supplementation, and assess the effect of the surgical procedure on 25(OH)D level following supplementation.

METHODS

We searched Medline, PubMed, the Cochrane Library and EMBASE, for relevant observational studies published in English, from 2000 to April 2015. The identified references were reviewed, in duplicate and independently, by two reviewers.

RESULTS

We identified 51 eligible observational studies assessing 25(OH)D status pre and/or post bariatric surgery. Mean pre-surgery 25(OH)D level was below 30ng/ml in 29 studies, and 17 of these studies showed mean 25(OH)D levels ≤20ng/ml. Mean 25(OH)D levels remained below 30ng/ml following bariatric surgery, despite various vitamin D replacement regimens, with only few exceptions. The increase in post-operative 25(OH)D levels tended to parallel increments in vitamin D supplementation dose but varied widely across studies. An increase in 25(OH)D level by 9-13ng/ml was achieved when vitamin D deficiency was corrected using vitamin D replacement doses of 1100-7100IU/day, in addition to the usual maintenance equivalent daily dose of 400-2000IU (total equivalent daily dose 1500-9100IU). There was no difference in mean 25(OH)D level following supplementation between malabsorptive/combination procedures and restrictive procedures.

CONCLUSION

Hypovitaminosisis D persists in obese patients undergoing bariatric surgery, despite various vitamin D supplementation regimens. Further research is needed to determine the optimal vitamin D dose to reach desirable 25(OH)D levels in this population, and to demonstrate whether this dose varies according to the surgical procedure.

Calcium metabolism, vitamin D and bone mineral density after bariatric surgery

SUMMARY

Lower bone mineral density, vitamin D deficiency, lower lean body mass, greater loss of excess weight, and increased bone turnover are complications found after bariatric surgery correlated in the literature with increased risk of fractures. The prevention and treatment of such complications should begin immediately after surgery.

INTRODUCTION

The aims of the study were to evaluate bone mass in patients undergoing bariatric surgery by the Wittgrove technique after 1 year of the procedure and correlate it with body composition, weight loss, 25OH vitamin D levels, and markers of bone metabolism.

METHODS

The operated group (OG) participated in a clinical consultation; a blood sample taken and a body composition; and bone mineral density assessment by dual energy X-ray absorptiometry (DXA). The results were compared with a control group (CG).

RESULTS

Fifty-six subjects in the OG and 27 in the CG were included. The bone mineral density (BMD), after the surgery, at the lumbar spine (LS) was lower in the OG than in the CG. There was a positive correlation between total body (TB) BMD with 25OHD, body mass index (BMI), and lean mass and an inverse correlation with percentage of excess weight loss (%EWL). Vitamin D deficiency was seen in 60.41% (OG) and in 16.6% (CG). PTH was higher in the OG, with secondary hyperparathyroidism in 41.7%. In 26.5% and 14.2% of the OG, ALP and OC levels were above the reference values. In <50 years, elevated values of carboxy-terminal telopeptide (CTX) were found in 66.7% of patients. A difference was observed in the variation of CTX between 12 and 18 months when compared to over 24 months.

CONCLUSIONS

Lower BMD was observed, correlated with lower lean body mass and greater loss of excess weight. Vitamin D deficiency with high prevalence of secondary hyperparathyroidism and high bone turnover was detected. The prevention of bone loss should be initiated in the first months after surgery, which is a period associated with severe muscle loss and increased bone turnover.

[Changes in bone metabolism markers in women after Roux-en-Y gastric bypass]

OBJECTIVE

To evaluate bone turnover markers and bone mineral density (BMD) in women after Roux-en-Y (RYGB) gastric bypass.

SUBJECTS AND METHODS

In a cross-sectional study, 48 women post-RYGB after three years, and 41 healthy women were evaluated.

EVALUATIONS

body mass index (BMI); physical activity; food intake; serum levels of calcium, phosphorus, magnesium, alkaline phosphatase, C-terminal telopeptide (CTX), intact parathyroid hormone (PTH), 25-hydroxyvitamin D (25OHD), osteocalcin, urinary calcium and BMD.

RESULTS

Significantly higher levels were observed for osteocalcin (p < 0.001), CTX (p < 0.001), and PTH (p < 0.001) in the RYGB group when compared with the control group; 25OHD deficiency/insufficiency was more frequent in the RYGB group (p = 0.010), even after adjusted for nutritional status, and it was associated with secondary hyperparathyroidism (p = 0.025); there was no difference in BMD between the groups. Energy (p = 0.036) and protein intake (p = 0.004) were lower in the RYGB group.

CONCLUSION

Patients submitted to RYGB showed a significantly higher frequency of vitamin D deficiency, secondary hyperparathyroidism, and increase in bone remodeling markers, with no difference in BMD status.

Examining the link between bariatric surgery, bone loss, and osteoporosis: a review of bone density studies

As the popularity of bariatric surgery to treat morbid obesity has risen, so has a concern of increased skeletal fragility secondary to accelerated bone loss following bariatric procedures. We reviewed cross-sectional and prospective literature reporting bone density outcomes following bariatric surgical treatment for morbid obesity. Prospective research provides evidence of hip and lumbar spine areal bone mineral density (aBMD) reductions primarily in women despite calcium and vitamin D supplementation. Femoral neck aBMD declines of 9-11% and lumbar spine aBMD reductions up to 8% were observed at the first post-operative year following malabsorptive procedures. Mean T- and Z-scores up to 25 years following surgery remained within normal and healthy ranges. Of those studies reporting development of osteoporosis following gastric bypass, one woman became osteoporotic after 1 year. Despite observed bone loss in the hip region post-surgery, data do not conclusively support increased incidence of osteoporosis or increased fracture risk in post-bariatric patients. However, given the limitations of dual energy X-ray absorptiometry technology in this population and the relative lack of long-term prospective studies that include control populations, further research is needed to provide conclusive evidence regarding fracture outcomes in this population.

What every hospitalist should know about the post-bariatric surgery patient

Obesity is a growing worldwide epidemic, increasingly addressed through surgical options for weight loss. Benefits of these operations, such as weight loss and improvement or reversal of obesity-related comorbidities, are well established; however, postoperative complications do occur. This article will evaluate common causes for hospital admissions in the post-bariatric surgery population as they relate to the hospitalist who is often responsible for their care. Here we provide an overview of the most common bariatric procedures currently performed, early postoperative complications, late medical complications (ie, abdominal complaints, weight fluctuations, nutritional deficiencies, and metabolic bone disease), and late surgical complications that often affect these patients and result in hospital admissions. Special attention will be paid to radiologic pearls that can assist in the initial evaluation and diagnosis of these patients.

[Bariatric surgery, calcium oxalate urinary stones and oxalate nephropathy]

Bariatric surgery is now recognized as a sure and effective way for weight reduction in morbid obesity. However some procedures induce intestinal malabsorption leading to enteric hyperoxaluria. So bariatric surgery could place these patients not only at risk for nephrolithiasis but also for oxalate induced nephropathy and chronic renal failure. Because of the growing incidence of obesity worldwide, physicians and patients should be aware of such potential complications. There is no mean to discuss this treatment because of its spectacular efficiency on obesity and its comorbidities. But it is necessary to choose the surgical technique according to the risk factors of the patients. Following surgery, preventive treatment strategies are indicated, such as modified dietary lifestyle and specific drugs as we suggested to limit or even avoid these complications. However observance could fail in the long term. In case of oxalate nephropathy, surgery may be proposed to restore the intestinal tract but with the risk of overweight relapse. To illustrate this matter, we report here significant observations of three patients, which, having successfully benefited from the same bariatric surgery, have presented lithiasic complications for two of them and oxalate nephropathy leading to chronic renal failure and hemodialysis for the third.

[Bone mass loss after sleeve gastrectomy: a prospective comparative study with gastric bypass]

INTRODUCTION

Bariatric surgery is the most effective option for the treatment of patients with a high risk of complications due to their obesity. However, it brings about a series of changes in calcium and vitamin D metabolism and an increase in resorption which lead to a loss of bone mass.

AIM

The objective of this study is to compare sleeve gastrectomy (SG) and Roux-en-Y gastric bypass (RYGB) as regards loss of bone mass using bone densitometry and bone remodelling markers.

PATIENTS AND METHODS

Fifteen women with morbid obesity were included, 8 by SG and 7 by RYGB, with a mean age of 47.8+/-9 and mean body mass index 43.3+/-3.4. Bone mass measurements were made on the lumbar spine, femur and distal radius, and the bone remodelling markers N-telopeptide (NTx) and bone alkaline phosphatase (BALP), as well as vitamin D levels before and 12 months after surgery.

RESULTS

A significant bone mass loss was observed was observed with SG and RYGB, in the lumbar spine and hip, whilst no differences were observed in the radial. The percentage bone mass loss was less in the column and femur after SG than with RYGB, although it did not reach statistical significance, 4.6%+/-4.4 (mean+/-SD) and 6.3%+/-5.4 (mean+/-SD), respectively. At 12 months the Ntx increased for both types of surgery, and the BAP was only increased for SG.

CONCLUSION

SG causes less, although not significant, bone mass loss compared to RYGB.

Factors associated with secondary hyperparathyroidism in premenopausal women undergoing Roux-en-Y gastric bypass for the treatment of obesity

OBJECTIVE: To evaluate bone metabolism, bone density (BMD) and vertebral fractures in morbidly obese individuals. SUBJECTS AND METHODS: Case series of 29 premenopausal obese patients, 15 of whom had been submitted to bariatric surgery. Serum calcium, albumin, PTH and 25-hydroxy vitamin D (25OHD) were measured as well as bone densitometry of the lumbar spine and proximal femur, and lateral spine x-rays. RESULTS: High parathyroid hormone (PTH) levels were recorded in 46.6% of the surgical patients and in 21.4% of the non-surgical patients (p = 0.245); 26.7% of the former and 28.6% of the latter revealed levels 25OHD < 30 ng/mL (p = 1.000). Calcium intake was higher in the surgical group (p = 0.004) along with lower serum calcium concentrations (p = 0.019). There were no significant differences in bone mineral density (BMD) or in the prevalence of vertebral fractures between groups. CONCLUSION: In premenopausal women undergoing Roux-en-Y gastric bypass there is important intestinal calcium mal absorption which seems to be the main factor causing secondary hyperparathyroidism.

Adolescent obesity and bariatric surgery

PURPOSE OF REVIEW

Examines the effects of bariatric surgery on adolescent obesity.

RECENT FINDINGS

The risks and outcomes of bariatric surgery in adolescence are presently being defined and may be somewhat different from those in adults. Adolescents may have a greater risk of weight regain, and greater risk of noncompliance to treatment after surgery. However, long-term outcomes are not yet available, and the underlying metabolic benefits appear to be substantial and similar to those of adults.

SUMMARY

Morbid obesity in adolescents has severe acute and chronic complications. Bariatric surgery in adolescents seems as well tolerated as in adults when performed in centers with appropriate experience and adequate surgical volume. The pathophysiologic implications of bariatric surgery are profound. A better understanding of the mechanisms leading to postsurgical improvement in insulin resistance and weight loss could lead to the development of other therapies to achieve the same effects with lesser morbidities.

Nutritional deficiencies in morbidly obese patients: a new form of malnutrition? Part A: vitamins

It is a common belief that clinical vitamin or mineral deficiencies are rare in Western countries because of the low cost and unlimited diversity of food supply. However, many people consume food that is either unhealthy or of poor nutritional value that lacks proteins, vitamins, minerals, and fiber. In this, article we reviewed the literature and highlighted the vitamin deficiencies in obese patients before bariatric surgery. Deficiency of dietary minerals is described in the accompanying manuscript. The prevalence of vitamin deficiencies in the morbidly obese population prior to bariatric surgery is higher and more significant than previously believed.

Vitamin D therapy

The fat-soluble vitamin D prohormones, ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3), are essential for the efficient intestinal absorption of calcium and phosphate and the subsequent mineralization of bone. Inadequate vitamin D leads to chronic secondary hyperparathyroidism and osteoporosis. The increasing prevalence of osteoporosis has paralleled a pandemic of vitamin D insufficiency. Based on observational and prospective trials with clinical end points, the standards for vitamin D sufficiency have been recently revised. All patients with osteopenia or osteoporosis should be monitored with a reliable assay to maintain serum 25-hydroxyvitamin D levels more than 32 ng/dL. Patients who are taking bisphosphonates and those with coexisting primary hyperparathyroidism are not exempt from taking supplemental vitamin D.