Regulation of vitamin D and calcium metabolism after gastrectomy

Metabolic bone disorders after gastrectomy: inevitable or preventable?

Some authors have suggested that a relationship exists between gastrectomy for gastric cancer and metabolic bone disorders. However, few studies have investigated metabolic bone disorders after gastrectomy for gastric cancer in detail. Thus, we reviewed the findings of our recent prospective study and those of other reports on this subject. Osteoporosis and osteomalacia have been observed after gastrectomy and appear to be caused by reduced food intake and absorption, and steatorrhea. Moreover, the incidence of fracture is high after gastrectomy, although subtotal or total gastrectomy and reconstruction for gastric cancer have not been identified as significant risk factors for decreased bone mineral density (BMD). Recently, we reported that the BMD decreased significantly within 12 months after gastrectomy for gastric cancer in both male and female patients, but there was no significant gender-related difference in the rate of change in BMD. More than 1 year after gastrectomy, the steep decrease in the BMD stabilized and normal levels of 1,25(OH)₂ vitamin D₃ were maintained, despite the lack of precursor for 1,25(OH)₂ vitamin D₃ synthesis after gastrectomy. Alendronate therapy might be effective and prevent postgastrectomy metabolic bone disorders; however, the optimal treatment and prevention strategy for this bone disorder has not been delineated.

Long-term use of proton pump inhibitors as a risk factor for various adverse manifestations

The long-term use of proton pump inhibitors (PPIs) can lead to increased gastric pH, hypochlorhydria and in some cases to achlorhydria when compared to other acid-suppressing agents like histamine-2 (H2) receptor blockers and antacids. These consequences by the use of long-term PPIs may lead to significant vitamin (B₁₂ and C) and mineral (iron, calcium and magnesium) deficiencies which needs gastric acid for their absorption and bioavailability. Long-term use of PPIs by the pregnant patients may impose a potential risk of congenital malformations. Various studies have recommended the life style modifications and antacid use as first choice among pregnant womens by preserving PPIs (omeprazole as a safe choice of PPI) for severe conditions of gastroesophageal reflux disease. The long-term acid suppression by PPIs can also lead to enteric, respiratory and urinary tract infections. The hypochlorhydria by chronic PPIs use may induce hypergastrinemia, which ultimately mediates the gastric polyps, gastric carcinoids and gastric cancer. The concomitant use of PPIs with antiplatelet drugs like clopidogrel can impose the patients to major adverse cardiac events. This review has enlisted the comprehensive information regarding the adverse effects induced by long-term use of PPIs and their possible relations. Considerable studies like case-control, randomized trials, cohort studies and meta-analysis were reported in supporting these adverse effects. The clinicians and patients should be cautious about these effects so that they can avoid the serious outcomes. PPIs should be avoided for long-term use mainly in older adults unless there is a proper indication.

A Narrative Role of Vitamin D and Its Receptor: With Current Evidence on the Gastric Tissues

Vitamin D is a major steroid hormone that is gaining attention as a therapeutic molecule. Due to the general awareness of its importance for the overall well-being, vitamin D deficiency (VDD) is now recognized as a major health issue. The main reason for VDD is minimal exposure to sunlight. The vitamin D receptor (VDR) is a member of the steroid hormone receptors that induces a cascade of cell signaling to maintain healthy Ca²⁺ levels that serve to regulate several biological functions. However, the roles of vitamin D and its metabolism in maintaining gastric homeostasis have not yet been completely elucidated. Currently, there is a need to increase the vitamin D status in individuals worldwide as it has been shown to improve musculoskeletal health and reduce the risk of chronic illnesses, including some cancers, autoimmune and infectious diseases, type 2 diabetes mellitus, neurocognitive disorders, and general mortality. The role of vitamin D in gastric homeostasis is crucial and unexplored. This review attempts to elucidate the central role of vitamin D in preserving and maintaining the overall health and homeostasis of the stomach tissue.

Long-term changes in the metabolic and nutritional parameters after gastrectomy in early gastric cancer patients with overweight

BACKGROUND

With the increase in the prevalence of overweight, percentage of overweight patients with gastric cancer has also increased. This 5-year retrospective cohort study was performed to investigate long-term changes in the metabolic and nutritional parameters of early gastric cancer (EGC) patients with overweight after gastrectomy.

METHODS

EGC patients who underwent gastrectomy were followed up over a 5-year period. We included 393 patients (261 men, 132 women) who had an initial body mass index (BMI) of ≥23 kg/m², and analyzed the longitudinal changes in the metabolic and nutritional parameters.

RESULTS

Body weight and random glucose, alanine aminotransferase (ALT), hemoglobin, and serum calcium levels significantly decreased, while serum protein and albumin levels increased in both men and women after gastrectomy. The odds ratios (ORs) for BMI ≥ 25 kg/m² (P < 0.001 for men and women), random glucose ≥ 126 mg/dL (men; P = 0.001, women; P < 0.001), and ALT > 40 IU/dL (men; P < 0.001, women; P = 0.018) were lower in both men and women after 5 years. The ORs for low protein and albumin levels decreased, although the ORs for anemia and hypocalcemia increased in both sexes at 5 years after gastrectomy.

CONCLUSION

Gastrectomy in overweight patients followed up over 5-year could lead to approximately 10% weight loss and favorable changes in the metabolic parameters in both men and women. The risk of anemia and hypocalcemia increased, and the risk of low protein and albumin levels decreased in both sexes.

Proton pump inhibitors and risk of bone fractures

OPINION STATEMENT

There are 34 studies in almost 2 million participants that have reported on the association between proton pump inhibitor (PPI) therapy and risk of fracture. There is substantial variation between the results of each study but systematic reviews of the data suggest overall there is an association between PPI therapy and risk of fracture. The magnitude of the association is modest and is most likely due to confounding factors as patients prescribed PPI therapy tend to be more frail with more risk factors for fractures than those not given these drugs. There is no clear dose-response relationship and there is no association between PPI therapy and risk of fracture in those at highest risk. Finally, there is no clear mechanism through which PPI therapy increases the risk of fracture, as recent randomized trials show no impact of PPI therapy on calcium absorption and there is no association between PPI therapy and risk of osteoporosis. We therefore feel there is insufficient evidence to change PPI prescribing habits based on risk of fracture. Similarly, we do not recommend bone mineral density investigations for patients taking PPI therapy other than would be normally indicated. There is no evidence to support prescription of calcium and/or vitamin D in patients simply because they are taking PPI therapy. As with all medications, we only recommend prescribing PPI therapy when there is a clear indication that benefit will outweigh risk and at the lowest effective dose. Patients should be regularly assessed as to whether acid suppression is still required.

[Long-term proton pump inhibitor therapy and osteoporosis. Is there a real danger?]

Proton pump inhibitors are widely used in the treatment of acid-related diseases because they are considered to be effective and safe. In the past 10 years the use of proton pump inhibitors increased by over three folds, which is not associated with the increased prevalence of acid-related diseases obviously. However, like any other drugs, they have potential side effects. In recent years many studies have been published about the correlation between long-term proton pump inhibitor therapy and the increase of bone fractures. Most studies showed that long-term proton pump inhibitor therapy moderately increased fracture risk. The underlying mechanisms of increased number of bone fractures are not clarified yet. However, chronic acid suppression caused by long-term proton pump inhibitor therapy may play a crucial role in decreased absorption of calcium and vitamin B12 and, therefore, indirectly affecting the bones resulting in a decrease of bone mineral density. The available data suggest that proton pump inhibitors should be used with caution in patients with increased risk of osteoporosis.

Indications and safety of proton pump inhibitor drug use in patients with cancer

INTRODUCTION

Although the exact prevalence of proton pump inhibitor (PPI) use in cancer patients is not known, it is generally perceived to be widespread. PPIs are generally well tolerated and carry an excellent safety profile. However, increasing and longer term PPI use has raised concerns about the risk of pneumonia, bone fractures and enteric infections, and a possible interaction with clopidogrel that could increase the risk of cardiovascular events.

AREAS COVERED

We conducted a PubMed search of English language articles addressing the safety and adverse events associated with PPI use with particular emphasis in cancer patients.

EXPERT OPINION

PPIs, frequently used in cancer patients, are generally well tolerated and carry an excellent safety profile. PPI-induced acid suppression may increase the risk of Clostridium difficile or other enteric infections, nutritional deficiencies and community acquired pneumonia, all particularly important in cancer patients. The indications for PPI use in cancer patients should be carefully reviewed prior to use.

Iatrogenic osteomalacia: report of two cases

CASE 1: An 80-year-old man presented at our hospital with pain in both knees.He had received continuous intravenous administration of saccharated ferric oxide (SFO) over a period of five years following a diagnosis of iron-deficiency anemia.Blood tests revealed hypophosphatemia (1.4 mg/dl) and high circulating levels of fibroblast growth factor 23 (FGF23) at 248.8 mg/dl.These findings led to the diagnosis of FGF23-related osteomalacia due to SFO administration.Accordingly, the treatment plan was first to discontinue SFO, which led to a decrease in pain and normalization of phosphorus and FGF23 after 1 month.CASE 2: A 63-year-old woman presented at our hospital with leg pain.She had undergone total gastrectomy for gastric cancer at 36 years of age.Blood tests revealed hypocalcemia (8.3 mg/dl) and hypophosphatemia (2.2 mg/dl), and 25(OH)D at no more than 5 pg/ml.Bone X-rays showed significantly diminished bone shadowing.These findings led to a diagnosis of vitamin D-deficient osteomalacia due to impaired absorption following total gastrectomy.For therapy, she was treated with 1 μg/day oral alfacalcidol.Two months after initiating treatment, the pain improved.

CONCLUSION

When a patient is diagnosed with unexplained pain, it is important to pay attention to the possibility of an iatrogenic etiology.

Gastric acid, calcium absorption, and their impact on bone health

Calcium balance is essential for a multitude of physiological processes, ranging from cell signaling to maintenance of bone health. Adequate intestinal absorption of calcium is a major factor for maintaining systemic calcium homeostasis. Recent observations indicate that a reduction of gastric acidity may impair effective calcium uptake through the intestine. This article reviews the physiology of gastric acid secretion, intestinal calcium absorption, and their respective neuroendocrine regulation and explores the physiological basis of a potential link between these individual systems.

Chronic proton pump inihibitor therapy and calcium metabolism

Proton pump inhibitors (PPIs) have been widely used since their introduction in the late 1980s because they are highly effective for acid-related conditions. However, some recent epidemiological studies have suggested a positive association between PPI therapy and the risk of osteoporotic fractures. The potential mechanisms underlying this association may be related to the physiologic effects of chronic acid suppression on calcium metabolism. First, chronic hypergastrinemia induced by PPI therapy may lead to parathyroid hyperplasia, resulting in increased loss of calcium from the bone. Second, profound gastric acid suppression may reduce the bioavailability of calcium for intestinal absorption. I will review the published evidence regarding these potential links and discuss their clinical implications.

The risks of PPI therapy

PPIs have become one of the most commonly used medications worldwide, as they are the treatment of choice for several acid-related gastrointestinal disorders. However, concerns have been raised about PPI therapy, including the risk of pneumonia, bone fractures and enteric infections, and a possible interaction with clopidogrel that could increase the risk of cardiovascular events. Observational studies have shown very modest associations between PPI therapy and these risks, although the association between PPI treatment and the risk of enteric infections seems to be stronger than the association with other risk factors. However, given the inherent limitations of observational studies, these associations could be attributable to bias and/or confounding factors. In addition, evidence from randomized, controlled trials does not support a clinically significant effect of PPI therapy on the risk of cardiovascular events in patients taking clopidogrel or the risk of pneumonia. Nevertheless, it is impossible to exclude the possibility that some of these associations might be causal or indeed that PPI therapy has an as yet unknown long-term adverse effect. As with any therapy, therefore, it is advisable to prescribe PPIs only to patients for whom these drugs have been proven beneficial.

Dietary galactooligosaccharides increase calcium absorption in normal and gastrectomized rats

OBJECTIVE

To determine whether the galactooligosaccharide stimulates calcium absorption in partially gastrectomized rats.

METHODS

Animals were submitted to laparotomy (sham-operated control) and partial gastrectomy (Billroth II) in groups of 20. They were fed a control diet (AIN-93M) without galacto-oligosaccharide or a diet containing (galacto-oligosaccharide - 50 g/kg diet) for eight weeks. The animals were divided into four groups: sham-operated and non-gastrectomized with galactooligosaccharide, sham-operated and gastrectomized without galactooligosaccharide. On the final day of the study, whole blood was collected for determination of serum calcium concentration.

RESULTS

In the group with galactooligosaccharides calcium excretion in feces was significantly lower than the group without prebiotics. The apparent absorption of calcium in gastrectomized and normal rats was higher in groups fed with galactooligosaccharide than in the control diet group.

CONCLUSION

The ingestion of galactooligosaccharides prevents osteopenia in partially gastrectomized rats.

Adverse effects of long-term proton pump inhibitor therapy

Proton pump inhibitors have an excellent safety profile and have become one of the most commonly prescribed class of drugs in primary and specialty care. Long-term, sometimes lifetime, use is becoming increasingly common, often without appropriate indications. This paper is a detailed review of the current evidence on this important topic, focusing on the potential adverse effects of long-term proton pump inhibitor use that have generated the greatest concern: B12 deficiency; iron deficiency; hypomagnesemia; increased susceptibility to pneumonia, enteric infections, and fractures; hypergastrinemia and cancer; drug interactions; and birth defects. We explain the pathophysiological mechanisms that may underlie each of these relationships, review the existing evidence, and discuss implications for clinical management. The benefits of proton pump inhibitor use outweigh its risks in most patients. Elderly, malnourished, immune-compromised, chronically ill, and osteoporotic patients theoretically could be at increased risk from long-term therapy.

Safety of proton pump inhibitor exposure

Proton pump (H(+)/K(+)-adenosine triphosphatase) inhibitors (PPIs) are widely used to treat patients with acid-related disorders because they are generally perceived to be safe and effective. However, as with any pharmacologic agent, they have the potential for side effects. Many studies have examined the side effects of long-term or short-term PPI exposure. We review the mechanism of action of PPIs, focusing on recently released products that might have greater risks of adverse effects than older products because of increased potency and/or duration of action. We summarize the data available on the putative adverse effects of PPI therapy and propose guidelines for clinicians who prescribe these agents to limit the potential for adverse outcomes in users of these effective therapeutic agents.

Isolation and characterization of a novel peptide, osteoblast activating peptide (OBAP), associated with osteoblast differentiation and bone formation

A long-standing goal in bone loss treatment has been to develop bone-rebuilding anabolic agents that can potentially be used to treat bone-related disorders. To purify and isolate a novel anabolic that acts to osteoblasts, we monitored changes in intracellular calcium concentrations ([Ca(2+)]i). We identified a novel, 24 amino-acid peptide from the rat stomach and termed this peptide osteoblast activating peptide (OBAP). Furthermore, we examined the effects of OBAP in osteoblasts. First, osteoblast differentiation markers (alkaline phosphatase [ALP], osteocalcin [OCN]) were analyzed using quantitative RT-PCR. We also examined the ALP activity in osteoblasts induced by OBAP. OBAP significantly increased the expression of osteoblast differentiation markers and the activity of ALP in vitro. Next, to address the in vivo effects of OBAP on bone metabolism, we examined the bone mineral density (BMD) of gastrectomized (Gx) rats and found that OBAP significantly increased BMD in vivo. Finally, to confirm the in vivo effects of OBAP on bone, we measured serum ALP and OCN in Gx rats and found that OBAP significantly increased serum ALP and OCN. Taken together, these results indicate that the novel peptide, OBAP, positively regulates bone formation by augmenting osteoblast differentiation. Furthermore, these results may provide a new therapeutic approach to anabolically treat bone-related disorders.

Dietary polydextrose increases calcium absorption in normal rats

BACKGROUND: Gastric surgery is known to cause bone disorders, possibly related to an impaired capacity for the absorption of dietary calcium. AIM: To verify if polydextrose (PDX) could stimulate calcium absorption in partially gastrectomized and sham operated rats. METHODS: The rats were laparotomized (sham-operated control) or partially gastrectomized (Billroth II), in groups of 20 each. Half in each operated group were fed a control diet (AIN-93M) without PDX or the same diet containing (PDX 50g/Kg of diet) for eight weeks. The rats were divided into four subgroups: sham-operated and gastrectomized without PDX; sham-operated and gastrectomized with PDX. On the final day of the study, total blood was collected for determination of serum calcium concentration. RESULTS: In the diet with PDX, excretion of calcium in the feces was significantly lower than in the groups not receiving PDX, irrespective of the operation. Apparent calcium absorption and serum calcium was higher in the sham operated PDX fed group than in the control group. In sham operated rats, the calcium concentration in bone was higher in the PDX fed group. CONCLUSION: The polydextrose feeding increased calcium absorption and bone calcium concentration in normal rats, which may be relevant for decreasing the risk of osteoporosis. Partially gastrectomy did not affect the bone calcium concentration in 56 days of experimental period.

Vitamin D deficiency after highly selective vagotomy

While bone disease is occasionally seen after gastrectomy, the influence of vagotomy on calcium and vitamin D metabolism is uncertain. We have, therefore, investigated 23 male patients who had undergone highly selective vagotomy for ulcer 4.3 +/- 1.2 years previously. The 25OHD concentrations were decreased (p less than 0.05), the 1,25(OH)2D concentrations elevated (p less than 0.05) and the immunoreactive parathyroid hormone concentrations normal. Local and total bone mass were normal compared to age-matched men, and there was no biochemical evidence of increased bone turnover. We suggest that the changes in calcium absorption, which are described in the literature after vagotomy, are mediated by 1,25(OH)2D. Although the changes in vitamin D metabolism do not lead to calcium-metabolic disturbances in selected patients, we believe that some will eventually develop vitamin D deficiency and that vitamin D supplementation should be considered.

3-Hydroxy-3-methylbutyrate administration diminishes fundectomy-induced osteopenia of the lumbar spine in pigs

OBJECTIVE

The aim of the study was to test the hypothesis that oral administration with 3-hydroxy-3-methylbutyrate (HMB) positively influences bone metabolism and diminishes fundectomy-induced osteopenia of the axial skeleton in pigs. The pig model was chosen because of its recognized physiologic and anatomic similarities of the gastrointestinal tract and skeletal system to those of humans.

METHODS

Eighteen male pigs were divided into three weight-matched groups at 40 d of life. Animals from the first and second groups were subjected to experimental fundectomy and the third group was sham operated. Starting the day after the fundectomy, the first and second groups received placebo and HMB, respectively. Animals were sacrificed at the age of 8 mo to obtain L(5) and L(6) vertebrae for analysis. The effects of HMB administration on plasma amino acids concentrations, bone mineral density, morphology, and mechanical properties of the lumbar vertebrae were determined.

RESULTS

The HMB treatment increased the weight of the vertebrae, bone mineral density, bone mineral content, total bone volume, trabecular bone mineral density, mean volumetric bone mineral density, calcium hydroxyapatite density in the trabecular and cortical bones, and plasma amino acid concentrations in the fundectomized pigs (P < 0.05). Mechanical strength of the spine, expressed by the values of ultimate force, Young's modulus, ultimate stress, stiffness, and work to the ultimate force point was increased in HMB-treated pigs (P < 0.05).

CONCLUSION

HMB administration to fundectomized pigs improved plasma amino acids concentrations and diminished development of fundectomy-induced osteopenia of the axial skeleton.

Changes in vitamin D after gastrectomy

BACKGROUND

We previously reported that the administration of 1alpha hydroxy vitamin D3 was effective for treating post-gastrectomy bone disorders. Accordingly, we performed the present study to obtain evidence supporting the effectiveness of 1alpha hydroxy vitamin D3 in post-gastrectomy patients.

METHODS

The study involved 22 outpatients who had undergone gastrectomy for gastric cancer and had not been treated with 1alpha hydroxy vitamin D3 or calcium. They comprised 17 men and 5 women, with a mean age of 61.9 years. Laboratory tests were performed to examine the following parameters: 1,25(OH)(2) vitamin D3; 25(OH) vitamin D3; 24,25(OH)(2) vitamin D3; ionized calcium; calcium; phosphorus; alkaline phosphatase; N-parathyroid hormone; and osteocalcin.

RESULTS

The level of 1,25(OH)(2) vitamin D3, the most active of the vitamin D metabolites, was found to be normal in all of the patients. In contrast, the level of 25(OH) vitamin D3, which shows weak activity, was below the normal range in 7 of the 22 patients (31.8%). The mean serum level of 25(OH) vitamin D3 was significantly lower in patients at 1 year or more postoperatively than the level in those at less than 1 year postoperatively (P = 0.041), as well as being significantly lower in patients who had received total gastrectomy than in patients who underwent other gastrectomy procedures. The level of 24,25(OH)(2) vitamin D3, a metabolite of 25(OH) vitamin D3 that shows weak activity, was below the normal range in 19 of the 22 patients (86.4%). On multivariate analyses, factors associated with the change in vitamin D metabolites did not remain.

CONCLUSION

The patients showed a decrease of 25(OH) vitamin D3 and 24,25(OH)(2) vitamin D3, which are metabolites that show weak activity. This suggests that a homeostatic response maintains the normal level of 1,25(OH)(2) vitamin D3, which is important for calcium regulation. Thus, it was suggested that gastrectomy had a moderate influence on the metabolism of vitamin D. However we could not detect any factor associated with the decrease of 25(OH) vitamin D3 and 24,25(OH)(2) vitamin D3.

Ingestion of the soluble dietary fibre, polydextrose, increases calcium absorption and bone mineralization in normal and total-gastrectomized rats

We previously demonstrated that feeding a highly fermentable and water-soluble dietary fibre, guar-gum hydrolysate (GGH) increased intestinal absorption of insoluble Ca salts in total-gastrectomized rats. In the present study, we examined the effects of feeding a less fermentable and water-soluble fibre, polydextrose (PD), on Ca absorption and bone mineralization in the normal and total-gastrectomized rats in comparison with the effects of GGH. Apparent Ca absorption was severely lowered by gastrectomy, and PD feeding (50 g/kg diet) partially restored the reduction of Ca absorption similarly to GGH feeding (50 g/kg diet). PD feeding also increased the Ca absorption in normal rats, but not GGH feeding. Femur Ca concentration was reduced with gastrectomy. Feeding PD for 21 d increased the bone Ca concentration in both normal and gastrectomized rats, but GGH feeding did not. In rats fed PD, pH of the caecal contents was lower than in rats fed fibre-free and GGH diets; however, soluble Ca concentration in the caecal contents was not different between the diet groups. Short-chain fatty acid concentrations were much lower in the PD groups than in the GGH groups. We also examinedin vitroCa absorption by using everted sacs of the small intestine. Addition of PD to the serosal medium of the ileal sacs increased Ca absorption, but addition of GGH did not. These results suggest that the small intestine rather than the large intestine is responsible for the increase in Ca absorption in rats fed PD, and suggests that the mechanism for the increase by PD may be different from that by GGH.

Postgastrectomy syndromes--diagnosis and treatment

The stomach has a variety of functions that are lost with gastrectomy. Since nowadays a significant number of patients are long-term survivors, consequences of this loss need to be considered by gastroenterologists and surgeons alike. Abnormal transit, disturbed general nutrition and micronutrient deficiencies are the most common problems. The main resulting symptoms are early and late dumping, reflux esophagitis, weight loss, anemia, and osteopathy. It is not definitively clear if pouch reconstruction can really improve the situation. Dietary measures, rarely re-operation, and in particular adequate follow-up of metabolic and nutrition parameters with consequent substitution are the main therapeutic necessities.

Bone metabolism and risk of secondary hyperparathyroidism 12 months after gastric banding in obese pre-menopausal women

OBJECTIVE

To evaluate, during the first postoperative year in obese pre-menopausal women, the effects of laparoscopic gastric banding on calcium and vitamin D metabolism, the potential modifications of bone mineral content and bone mineral density, and the risk of development of secondary hyperparathyroidism.

SUBJECTS

Thirty-one obese pre-menopausal women aged between 25 and 52 y with a mean body mass index (BMI) of 43.6 kg/m(2), scheduled for gastric banding were included. Patients with renal, hepatic, metabolic and bone disease were excluded.

METHODS

Body composition and bone mineral density (BMD) were measured at baseline, 6 and 12 months after gastric banding using dual-energy X-ray absorptiometry. Serum calcium, phosphate, alkaline phosphatase, aspartate aminotransferase, alanine aminotransferase, gamma-glutamyltransferase, bilirubin, urea, creatinine, uric acid, proteins, parathormone, vitamin D(3), IGF-1, IGF-BP3 and telopeptide, as well as urinary telopeptide, were measured at baseline and 1, 3, 6, 9 and 12 months after surgery.

RESULTS

After 1 y vitamin D3 remained stable and PTH decreased by 12%, but the difference was not significant. Serum telopeptide C increased significantly by 100% (P<0.001). There was an initial drop of the IGF-BP3 during the first 6 months (P<0.05), but the reduction was no longer significant after 1 y. The BMD of cortical bone (femoral neck) decreased significantly and showed a trend of a positive correlation with the increase of telopeptides (P<0.06). The BMD of trabecular bone, at the lumbar spine, increased proportionally to the reduction of hip circumference and of body fat.

CONCLUSION

There is no evidence of secondary hyperparathyroidism 1 y after gastric banding. Nevertheless biochemical bone markers show a negative remodelling balance, characterized by an increase of bone resorption. The serum telopeptide seems to be a reliable parameter, not affected by weight loss, to follow up bone turnover after gastroplasty.

Does bone change after biliopancreatic diversion?

This prospective study evaluated bone changes after biliopancreatic diversion (BPD) consisting of a distal gastrectomy, a 250 cm alimentary channel, and a 50 cm common channel. Thirty-three consecutive patients had clinical, biochemical, and bone mineral density analysis before surgery and 4 and 10 years after surgery. Iliac crest bone biopsies and special tests including parathyroid hormone (PTH), 25-hydroxyvitamin D (25-OH-D), 1,25-dihydroxyvitamin D (1,25-OH(2)-D), bone-specific alkaline phosphatase (BAP), and osteocalcin were obtained at surgery and 4 years postoperatively. Over the years, with close metabolic surveillance, additional calcium and vitamin D were given as indicated. After BPD, serum levels of calcium and vitamin D were decreased and serum levels of PTH, BAP, and osteocalcin were increased. Bone turnover and mineralization were both increased. Mean osteoid volume (P < 0.0007) and bone formation rate in relation to bone volume (P < 0.02) were increased. Static measures of bone were altered as follows: cortical thickness decreased (P < 0.01) and trabecular bone volume increased (P < 0.01). Ten years after surgery, overall bone mineral density was unchanged at the hip and was decreased by 4% at the lumbar spine. Overall fracture risk, based on the Z score, was unchanged. Preoperative factors predicting bone loss included menopause, smoking, and preexisting osteopenia. An elevated level of 1,25-OH(2)-D was also found to be a predictor of future bone loss (r = 0.40; P < 0.002). After surgery, a greater increase in bone markers and bone turnover was associated with an increased risk of bone loss. Although elevated osteocalcin levels were associated with overall bone loss (r = 0.52; P < 0.002), lower albumin levels were associated only with bone loss at hip level (r = 0.44; P < 0.02), whereas lower calcium levels were associated only with the loss at the lumbar spine (r = 0.39; P < 0.02). Ten years after surgery, bone loss at the hip continued to depend on albumin levels (r = 0.37; P < 0.03). We concluded that bone was relatively tolerant to the metabolic changes due to BPD. Provided that there is close surveillance for metabolic disturbances, the use of appropriate supplements, and the avoidance of malnutrition, the beneficial effects of surgery far outweigh the risk of postoperative bone disease.

Early phase metabolic bone disorders after gastrectomy: influence of active vitamin D treatment

Metabolic bone disorders are recognized as one of the late complications after gastrectomy. However, the onset time and the extent of bone disorders are still unknown. We examined the influence of active vitamin D treatment on bone metabolism in the early period after gastrectomy. Sixty-three postgastrectomy patients were divided into two groups; active vitamin D treatment group [VD(+)] and no treatment group [VD(-)]. The level of serum calcium and phosphate was increased in the VD(+) group compared with the preoperative level, and parathyroid hormone (PTH-M) was decreased in the VD(+) group. Both 1,25-(OH)2D3 and bone-specific alkaline phosphatase (B-ALP) were increased in the VD(-) group. Cross-linked carboxyterminal telopeptide of type I collagen (I-CTP) was increased in the VD(+) group. There was no change in calcitonin in either group. In conclusion, metabolic bone disorders after gastrectomy have their onset in the early period, and active vitamin D treatment from the early period may be effective in preventing bone disorders.

Vitamin D nutrition and bone disease in adults

The consequences of vitamin D deficiency upon the skeleton are well known and management in the absence of renal failure is relatively straightforward. Vitamin D, either by mouth or parenterally will correct the deficiency and heal the osteomalacia. The mechanisms underlying the causation of vitamin D deficiency are now better understood and indicate the importance of underlying calcium malabsorption and secondary hyperparathyroidism leading to 1,25(OH)2D-induced catabolism of 25(OH)D and possibly also of vitamin D itself. In such situations, e.g., gastrointestinal and pancreaticobiliary disease, calcium supplementation in addition to vitamin D is indicated. The reasons behind nutritional vitamin D deficiency and the possible role of meat in protecting from osteomalacia await further elucidation, but from epidemiological studies, calcium deficiency, per se, is not implicated in the etiopathogenesis. The concept of vitamin D insufficiency is poorly understood, and difficult to define since a single value or close range of serum 25(OH)D values is unlikely to predict the needs of all subjects. Oral calcium intake and renal function are also likely to be relevant to the level of 25(OH)D which is found to be sufficient or insufficient for any given individual to maintain a normal serum calcium level without secondary hyperparathyroidism. There is increasing evidence that vitamin D insufficiency, by leading to sustained hyperparathyroidism, is prejudicial to the skeleton, particularly cortical bone. Since it is without symptoms until fractures occur, it should be actively sought in those clinical situations now recognized as contributing to risk. It can only be identified by the periodic measurement of serum 25(OH)D and the calcitropic hormones PTH and 1,25(OH)2D. In addition, BMD should be measured in a predominantly cortical site such as the proximal forearm, as well as the more conventional sites of spine and hip. The implications of these recommendations are an increase in the use of assays for PTH and vitamin D metabolites in the groups of subjects discussed in this review. Patients with chronic malabsorption states might reasonably be expected to have measurements performed twice-yearly. When vitamin D insufficiency is found, treatment with either vitamin D, calcium or both will be necessary, depending on the etiology of the insufficiency state in the inividual. In some malabsorptive states, calcium malabsorption is the cause of hyperparathyroidism and oral calcium alone can be used to reverse excess PTH activity in those with an adequate state of vitamin D nutrition. However, even in those vitamin D replete individuals, vitamin D catabolism will be enhanced and a small additional oral dose of vitamin D can do no harm. Regular monitoring of PTH and vitamin D metabolites will remain a necessity to ensure continued efficacy of treatment. Current recommendations for dietary supplements of vitamin D are clearly inadequate [61]. There is compelling evidence for supplements of 800 IU per day in the elderly and other high risk populations. Such a dose is safe and without side effects. The available evidence suggests that this should be combined with calcium supplements of 1200 mg/day [19] and that the current UK recommendations for a daily calcium intake of 700 mg contrast with those from the USA at 1,200 mg for people over 50 years old. Physicians need to be aware of both the small but important problem of vitamin D depletion and osteomalacia with its sometimes ambiguous presentation, and the more common but covert vitamin D (and calcium) insufficiency with its widespread and varied clinical associations.

Extracts of ECL-cell granules/vesicles and of isolated ECL cells from rat oxyntic mucosa evoke a Ca2+ second messenger response in osteoblastic cells

Surgical removal of the acid-producing part of the stomach (oxyntic mucosa) reduces bone mass through mechanisms not yet fully understood. The existence of an osteotropic hormone produced by the so-called ECL cells has been suggested. These cells, which are numerous in the oxyntic mucosa, operate under the control of circulating gastrin. Both gastrin and an extract of the oxyntic mucosa decrease blood calcium and stimulate Ca2+ uptake into bone. Conceivably, gastrin lowers blood calcium indirectly by releasing a hypothetical hormone from the ECL cells. The present study investigated, by means of fura-2 fluorometry, the effect of extracts of preparations enriched in ECL cell granules/vesicles from rat oxyntic mucosa on mobilization of intracellular Ca2+ in three osteoblast-like cell lines, UMR-106.01, MC3T3-E1 and Saos-2, and of extracts of isolated ECL cells in UMR-106.01 cells. The extracts were found to induce a dose-related rapid increase in intracellular Ca2+ concentrations in the osteoblast-like cells. The response was not due to histamine or pancreastatin, known ECL cell constituents, and could be abolished by pre-digesting the extracts with exo-aminopeptidase. The results show that the increase in [Ca2+](i) reflects a mobilization of Ca2+ from the endoplasmic reticulum. The observation of an increase in [Ca2+](i) also in murine embryonic fibroblasts show that the response is not limited to osteoblastic cells. The finding that the extracts evoked a typical Ca2+ -mediated second messenger response in osteoblastic cells provides evidence for the existence of a novel osteotropic peptide hormone (gastrocalcin), produced in the ECL cells, and supports the view that gastrectomy-induced osteopathy may reflect a lack of this hormone.

Ingestion of guar gum hydrolysate, a soluble fiber, increases calcium absorption in totally gastrectomized rats

Gastrectomy induces osteopenia. We examined the effects of feeding a diet containing soluble dietary fiber, guar gum hydrolysate (GGH, 50 g/kg diet), on intestinal calcium absorption and bone mineralization in totally gastrectomized (Roux-en-Y esophagojejunostomy) rats by comparing them with those in two control groups (laparotomized and bypassed rats). In the bypassed rats, chyme bypassed the duodenum and upper jejunum without gastrectomy. In a second separate experiment, we compared calcium absorption and bone mineralization in the gastrectomized rats fed diets containing soluble and insoluble calcium salts and in bypassed rats fed insoluble calcium. In Experiment 1, apparent absorption of calcium supplied as a water-insoluble salt was more than 50% lower in gastrectomized rats than in the intact (laparotomized) or bypassed rats 3 wk after the start of feeding the test diets (P < 0.05). Calcium absorption was higher (P < 0.05) in gastrectomized rats fed the GGH diet than in those rats fed the GGH-free diet. In Experiment 2, absorption of soluble calcium in the gastrectomized rats did not differ from the absorption of calcium from calcium carbonate by bypassed rats. The soluble calcium pool in the cecal contents was significantly lower in gastrectomized rats (Experiment 1) than in intact or bypassed control rats, and was higher (P < 0.05) in the GGH-fed gastrectomized rats than in those fed the GGH-free diet. However, calcium absorption correlated most closely (r = 0.787, P < 0.01) with cecal propionic acid concentration. The femur calcium content was significantly lower in gastrectomized rats fed insoluble calcium than in bypassed rats fed the same diet, but was partially restored in the rats fed soluble calcium (Experiment 2). Bone calcium was not increased by feeding GGH in gastrectomized rats (Experiment 1). We conclude that the severely diminished calcium absorption following total gastrectomy is totally due to a decrease in calcium solubilization, and feeding GGH partially restores calcium absorption. The decrease in bone calcium that occurs as a result of gastrectomy is mainly due to diminished intestinal calcium absorption.

Secondary osteoporosis

Generalized osteoporosis currently represents a heterogeneous group of conditions with many different causes and pathogenetic mechanisms, that often are variably associated. The term "secondary" is applied to all patients with osteoporosis in whom the identifiable causal factors are other than menopause and aging. In this heterogeneous group of conditions, produced by many different pathogenetic mechanisms, a negative bone balance may be variably associated with low, normal or increased bone remodeling states. A consistent group of secondary osteoporosis is related to endocrinological or iatrogenic causes. Exogenous hypercortisolism may be considered an important risk factor for secondary osteoporosis in the community, and probably glucocorticoid-induced osteoporosis is the most common type of secondary osteoporosis. Supraphysiological doses of corticosteroids cause two abnormalities in bone metabolism: a relative increase in bone resorption, and a relative reduction in bone formation. Bone loss, mostly of trabecular bone, with its resultant fractures is the most incapacitating consequence of osteoporosis. The estimated incidence of fractures in patients prescribed corticosteroid is 30% to 50%. Osteoporosis is considered one of the potentially serious side effects of heparin therapy. The occurrence of heparin-induced osteoporosis appeared to be strictly related to the length of treatment (over 4-5 months), and the dosage (15,000 U or more daily), but the pathogenesis is poorly understood. It has been suggested that heparin could cause an increase in bone resorption by increasing the number of differentiated osteoclasts, and by enhancing the activity of individual osteoclasts. Hyperthyroidism is frequently associated with loss of trabecular and cortical bone; the enhanced bone turnover that develops in thyrotoxicosis is characterized by an increase in the number of osteoclasts and resorption sites, and an increase in the ratio of resorptive to formative bone surfaces, with the net result of bone loss. Despite these findings, the occurrence of pathological fractures in patients with hyperthyroidism is relatively low, and probably due to the fact that deficiencies in bone mass may be reversed by treatment of the thyroid disease. Most, but not all, studies on insulin-dependent diabetes mellitus (IDDM) report an association with osteopenia. In IDDM, the extent of bone loss is usually slight, which helps explain the discrepancy between the frequency of decreased bone mineral density, and the frequency of osteoporotic fractures in long-standing diabetes. Contradictory results have been obtained in non-insulin-dependent diabetes mellitus (NIDDM) patients. Increased rates of bone loss at the radius and lumbar spine were demonstrated either in patients with two-thirds gastric resection and Billroth II reconstruction, or in those with one-third resection and Billroth I anastomosis, and the metabolic bone disease following gastrectomy may consist also of osteomalacia or mixed pattern of osteoporosis-osteomalacia, with secondary hyperparathyroidism. Miscellaneous causes of secondary osteoporosis are also immobilization, pregnancy and lactation, and alcohol abuse.

High prevalence of bone disorders after gastrectomy

BACKGROUND

Studies indicate that gastrectomy might alter calcium and bone metabolism, resulting in bone disorders. No data are currently available on the prevalence of bone disorders after gastrectomy.

METHODS

Sixty gastrectomy patients were investigated for serum parameters of calcium and bone metabolism 5 to 20 years postoperatively and compared to an age- and sex-matched healthy control population. Forty patients agreed to a radiological investigation of the spine by anterior-posterior and lateral radiographs of the thoracic and lumbar spine and by computed tomography (CT) osteodensitometry.

RESULTS

Serum calcium and 25-(OH)-vitamin D were decreased in gastrectomized patients, while parathyroid hormone and 1,25-(OH)2-vitamin D were increased. Serum parameters of calcium metabolism were altered in as many as 68% of patients. We found 31 vertebral fractures in 13 patients, 30 grade 2 vertebral deformities in 18 patients, and osteopenia in 15 patients, corresponding to a prevalence of 33%, 45%, and 37% in gastrectomized patients, respectively. The overall rate of gastrectomy patients having vertebral fractures and/or osteopenia was 55%. The risk of having a vertebral deformity was increased by more than sixfold after gastrectomy. Our study is the first report evaluating vertebral deformities in gastrectomized patients, and the largest series of gastrectomized patients investigated by CT osteodensitometry.

CONCLUSION

We found a high prevalence of bone disorders in gastrectomized patients, possibly resulting from disorders in calcium metabolism. Postgastrectomy bone disease might derive from a calcium deficit, which increases calcium release from bone and impairs calcification of newly build bone matrix.

Calcium regulation and bone mass loss after total gastrectomy in pigs

OBJECTIVE

Total gastrectomy often results in postgastrectomy bone disease with decreased bone mass and increased fracture risk. To further elucidate the mechanisms of postgastrectomy bone disease, the authors investigated calcium metabolism and bone mineral density after total gastrectomy in pigs.

SUMMARY BACKGROUND DATA

Postgastrectomy bone disease can present as osteomalacia, osteoporosis in excess of normal aging, or a combination of both. The underlying mechanisms are insufficiently understood and need further investigation.

METHODS

Growing minipigs were gastrectomized and compared with fed-matched, sham-operated control p gs for 1 year. Calcium absorption, serum calcium, parathyroid hormone, 25-(OH)-vitamin D, 1,25-(OH)2-vitamin D, alkaline phosphatase, and computed tomography bone mineral density were measured in three monthly intervals.

RESULTS

Total gastrectomy resulted in impaired calcium absorption, reduced serum calcium and 25-(OH)-vitamin D, increased parathyroid hormone and 1,25-(OH)2-vitamin, and reduced bone mineral density compared with fed-matched, sham-operated control pigs.

CONCLUSIONS

The authors data indicate that a reduced serum calcium activates counter-regulatory mechanisms, resulting in calcium mobilization from the bone. Possibly, calcium and vitamin D supplementation after total gastrectomy might prevent postgastrectomy bone mass loss.

Effects of vertical-banded gastroplasty on bone and mineral metabolism in obese patients

The surgical treatment of obesity can have adverse effects on bone, but there are few published data on the effects of vertical-banded gastroplasty. Serial measurements of bone mineral density at the lumbar spine and three upper femoral sites, using dual-energy X-ray absorptiometry, and also of biochemical indices of bone and mineral metabolism at intervals up to 2 years after operation were performed in 18 patients with morbid obesity who had vertical-banded gastroplasty. Bone mineral density measurements were also made in age- and sex-matched non-obese controls. Bone density before operation was significantly greater in the obese than in the controls (P < 0.02 at all sites). The obese patients lost weight rapidly after vertical-banded gastroplasty (mean weight loss 29 kg at 1 year, P < 0.001). This was accompanied by a measurable loss of bone density from the trochanter and Ward's triangle sites in the upper femur (P < 0.05), but not from the lumbar spine. Bone density values remained stable over 14 months in the controls. Hydroxyproline excretion increased significantly (P < 0.005), indicating an increase in bone resorption. Alkaline phosphatase levels decreased significantly (P < 0.001), but this probably represents the reversal of hepatic steatosis. There was no evidence of hyperparathyroidism or vitamin D deficiency. In conclusion, vertical-banded gastroplasty causes modest bone density loss from femoral sites, but not the lumbar spine. The difficulties of assessing bone density changes in the obese are discussed.

Chronological changes in bone mineral content following gastrectomy

Recent advances in the modalities of quantitatively assessing bone mineral content have resulted in an increasing awareness of metabolic bone disease as a late complication following gastrectomy. In this study, 98 postgastrectomy patients were examined by quantitative computed tomography (QCT). The bone mineral density index (BMDI), defined as 100 x (measured bone mineral density divided by that of age- and sex-matched controls), was used to evaluate the actual effect of gastrectomy on bone disorders. The BMDI values following gastrectomy were 80.4 +/- 27.3, with no significant difference between men and women, or between total and distal gastrectomy. Moreover, no significant differences were observed between the BMDI values within 6 months, being 92.6 +/- 37.3, and those 6 months to 1 year post gastrectomy, being 79.6 +/- 31.2; however, a significant and sharp decrease to 70.5 +/- 36.0 was evident after 1-2 years. The regression coefficient of the BMDI measured within 2 years postoperatively was lower than that measured after 2 years. These findings suggest that the influence of gastrectomy on bone metabolism is induced within 2 years, after which the bone mineral content decreases in accordance with physiological nature. Thus, we conclude that the treatment for bone disease resulting from gastrectomy would only be effective if initiated within a short period after surgery.

Structure of calvaria after gastrectomy. An experimental study in the rat

BACKGROUND

Gastrectomy induces bone loss, suggesting that the stomach is important for calcium homeostasis. In this study we examined the effects of gastrectomy, with or without CaCl2 supplementation, on the structure of the calvaria of the rat.

METHODS

The calvaria were dissected out and transilluminated, and the calvaria thickness was measured before (micrometer) and after fixation and sectioning (microscopy). Sections of the skull were analysed planimetrically for bone tissue area, using computer-assisted image analysis.

RESULTS

The time course of the gastrectomy-produced bone loss was studied. After 4 weeks the remaining bone represented about 70% of that in control rats, and after 8 weeks the value was 50%. The thickness of the calvaria was lower in gastrectomized rats than in sham-operated controls. Bone marrow and samples from liver and spleen were examined; no differences were found between experimental and control groups. Daily ingestion of 100 mg CaCl2.2H2O did not prevent the bone loss.

CONCLUSIONS

It is unlikely that the gastrectomy-produced bone loss reflects calcium deficiency. The results rather support the view that the stomach is important for calcium homeostasis through another mechanism, perhaps involving a hypothetical gastric hormone.

Postgastrectomy osteomalacia with pseudofractures assessed by repeated bone scintigraphy

A patient with osteomalacia secondary to vitamin D deficiency after gastrectomy for gastric cancer is presented. Initial bone scintigrams showed both asymmetric and symmetric focal areas of intense uptake due to pseudofractures reminiscent of bone metastases. Radiographs only confirmed the presence of pseudofractures at some, but not all, of the abnormal sites demonstrated by bone scintigraphy. At first, metastatic bone disease was suspected. However, the appearance of repeated bone scintigram was normalized after treatment with vitamin D. A diagnosis of osteomalacia was established. The present case serves to illustrate that symmetric focal lesions are important features of pseudofractures secondary to osteomalacia, and comparison with radiographs and repeated bone scintigraphy are necessary in distinguishing between bone metastases and pseudofractures.

Calcium solubilization and retention in the gastrointestinal tract in chicks (Gallus domesticus) as a function of gastric acid secretion inhibition and of calcium carbonate particle size

In chicks, immature pullets and laying hens, the inhibition of gastric acid secretion by omeprazole, an H+,K(+)-transporting ATPase (EC 3.6.1.36) inhibitor, greatly increased proventricular and gizzard pH values. Consequently, gizzard soluble Ca concentration deceased and the insoluble Ca fraction increased. Inhibition of acid secretion increased duodenal pH values in immature pullets and laying hens but not in chicks. Duodenal soluble and ionic Ca concentrations were lowered by gastric acid inhibition in chicks and to a larger extent in immature pullets and laying hens. The use of Ca of coarse particle size increased the gizzard insoluble Ca fraction in chicks and pullets. However, it did not influence its soluble Ca fraction in chicks but tended to reinforce the negative effect of omeprazole on soluble Ca in the gizzard and duodenum of chicks and laying hens. Coarse particles of Ca led to an increase in gizzard and duodenal soluble Ca at the end of eggshell calcification in laying hens. An enhancement in the level of Ca in the diet from 10 to 36 g/kg increased gizzard soluble Ca and duodenal soluble and ionic Ca concentrations in immature and adult hens. Intestinal Ca retention and bone mineralization was unaffected by gastric acid inhibition in chicks but were largely diminished by the use of coarse particles of Ca. Gastric acid inhibition was associated in laying hens with decreased Ca retention to a small extent and with reduced eggshell quality. These observations confirm that gastric acid secretion is of importance for CaCO3 solubilization but question its role as a prerequisite for intestinal Ca retention in chicks and even in hens fed on a high Ca diet.

Bone disorders following total gastrectomy

Bone disorders following gastrectomy were studied by measuring absolute and relative bone mineral density of the Wards triangle, serum 1,25-(OH)2-D, alkaline phosphatase, and total serum calcium. The subjects were 20 males who had undergone total gastrectomy not more than three months previously (group A1). Seventeen of these patients were reviewed three years later (group A2). Absolute and relative bone density were significantly lower in group A2 than in A1 (0.52 +/- 0.011 g/cm2 versus 0.6 +/- 0.014 g/cm2, P < 0.01 and 85.5 +/- 1.4% age-matched control versus 95 +/- 1.3%, P < 0.01). 1,25-(OH)2-D was significantly lower in group A2 than in group A1 (14.3 +/- 0.97 pg/ml versus 20.6 +/- 1.02 pg/ml, P < 0.01). There was no difference in alkaline phosphatase and calcium serum concentration. The mean weight loss was 6.26 +/- 0.57% over the follow-up period, and weight loss correlated with absolute and relative bone density (r = -0.74, P < 0.01). There was a positive correlation between 1,25-(OH)2-D and absolute or relative bone density (r = 0.67, r = 0.62 and P < 0.01). These data suggest that bone density decrease has already occurred three years after total gastrectomy and is positively correlated to 1,25-(OH)2-D deficiency. As no differences in serum alkaline phosphatase and serum calcium concentration were found, these factors are of little value for the early detection of postgastrectomy bone disorders, whereas weight loss is a valuable screening parameter.

Calcium regulating hormones and bone mineral content in patients after subtotal gastrectomy

Twenty-nine men who had undergone Billroth I gastrectomy and 19 men who had undergone Billroth II gastrectomy were studied to examine the changes in their calcium regulating hormones and bone mineral content following surgery. The serum calcium and phosphate concentrations in the patients with Billroth I and Billroth II were normal. The Billroth II group had an elevated level of serum alkaline phosphatase and reduced bone mineral content. The 24,25(OH)2D concentration was reduced (P < 0.01) and 25(OH)D and 1,25(OH)2D concentrations were increased (P < 0.01, P < 0.05, respectively) in the Billroth II group. It was suggested by our study that the Billroth II patients had a reduced bone mineral content and an elevated 1,25(OH)2D concentration. Therefore, the pathophysiology of postgastrectomy bone metabolic disease is not due to vitamin D deficiency, but may instead be due to reduced calcium absorption in the intestine.

Gastrectomy causes bone loss in the rat: is lack of gastric acid responsible?

Total gastrectomy or resection of the acid-producing part of the stomach (fundectomy) in the rat induced a marked and rapid reduction in bone wet weight, ash weight, and density (expressed as ash weight in mg/mm3 bone). Bone volumes were also affected but not as much. The radius, sternum, tibia, and femur were studied. Three weeks after gastrectomy the bone ash weight was reduced by almost 30% and the density by more than 25%. Maximum bone loss (approximately 40%) occurred about 6 weeks after the operation. The bone loss after gastrectomy was somewhat greater than that after fundectomy, whereas antrectomy had a marginal effect only. The percentage trabecular bone volume, calculated from morphometric analysis of histologic sections of the tibia, was greatly reduced by gastrectomy (approximately 50%), somewhat less so by fundectomy, whereas antrectomy had little effect. We set out to study whether calcium malabsorption could explain the bone loss after gastrectomy. Gastric acid is thought to facilitate the intestinal absorption of ingested calcium by mobilizing calcium from insoluble complexes in the diet. The possibility that lack of acid might contribute to the bone loss after gastrectomy was examined in experiments in which the proton pump inhibitor omeprazole was given for 4-8 weeks at such a dose (400 mumol/kg/day) that acid secretion was blocked almost completely during the period of study. This treatment was without effect on bone. However, the possibility could not be excluded that gastrectomized rats develop calcium deficiency for some reason other than lack of acid.(ABSTRACT TRUNCATED AT 250 WORDS)

Disturbances of mineral and bone metabolism following gastric antrectomy in the rat

In antrectomized (B-I) and control rats, bone mineralization, the fractional intestinal absorption of calcium, magnesium and phosphorus, the balances of these minerals, their serum concentration and renal excretion, together with serum gastrin, calciotropic hormones (parathyroid hormone, calcitonin, 1,25-dihydroxyvitamin D), and osteocalcin were assessed four months after surgery. B-I evoked hypogastrinemia, but no changes in the serum concentrations of minerals and calciotropic hormones, or urinary cyclic AMP. The major significant changes brought about by B-I were: (1) a decrease in bone dry weight, specific density, bone ash calcium and magnesium content; (2) a decrease in the fractional absorption and urinary excretion of calcium and magnesium; (3) an increase in urinary hydroxyproline and serum osteocalcin in the presence of normal serum bone isoenzyme of alkaline phosphatase. It is concluded that in the rat (1) B-I over the long term decreases both bone mineral content and calcium and magnesium absorption, in the absence of any counterregulation; (2) B-I rats may have attained a new equilibrium which is characterized by decreased absorption and urinary excretion of calcium and magnesium, but maintenance of normocalcemia at the expense of bone; (3) the concomitant changes of serum bone markers are contradictory, which makes their interpretation and use in the present context difficult.

A review of postgastrectomy bone disease

Postgastrectomy bone disease was a term devised to describe the metabolic disorders of bone which may follow a gastrectomy operation. Although the use of this operation has declined drastically in recent years, this metabolic bone disorder is still with us and may escape and confuse the unwary. These disorders may take the form of osteomalacia, osteoporosis in excess of normal ageing, or a combination of both. For screening purposes, regular estimations of plasma alkaline phosphatase levels identify patients who may be developing osteomalacia which can then be treated with calcium and vitamin D supplements. Numerically, osteoporosis in excess of ageing is a bigger problem and its prevention and treatment is at present unsatisfactory. Screening procedures for osteoporosis are reviewed, including the more recent methods of bone mineral density assessment. Osteopenia or demineralization occurs in both osteomalacia and osteoporosis therefore osteomalacia must be excluded before attributing any loss to osteoporosis. The present situation with regards to the prevention and treatment of osteoporosis is also reviewed.

The role of 1,25-dihydroxyvitamin D in the mechanism of acquired vitamin D deficiency

OBJECTIVE

We wished to assess the effect of changes in the plasma concentration of 1,25-dihydroxyvitamin D on the plasma elimination half-time for 25-hydroxyvitamin D in man.

DESIGN

The turnover of 25-hydroxyvitamin D in plasma was investigated after intravenous doses of the radioactively labelled metabolite had been given to a group of patients (n = 17) with disorders of bone and mineral metabolism before and after oral treatment with calcium or 1,25-dihydroxyvitamin D.

PATIENTS

Seven patients with post-menopausal osteoporosis, five with hypoparathyroidism, three with hypophosphataemic osteomalacia, one with renal osteodystrophy and one patient with coeliac disease were studied.

MEASUREMENTS

Intravenous injections of 3H-labelled 25-hydroxyvitamin D were given and plasma elimination half-time assessed over periods of 4-14 days during which frequent measurements of plasma calcium, phosphate, parathyroid hormone, 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D were made. Changes in the plasma elimination half-time for 3H-25-hydroxyvitamin D before and after treatment with calcium and 1,25-dihydroxyvitamin D were evaluated by non-parametric statistical analysis.

RESULTS

The elimination half-time for 3H-25-hydroxyvitamin D in plasma was significantly shortened by raising the circulating concentration of 1,25-dihydroxyvitamin D. Conversely, in a patient with intestinal malabsorption of calcium, the metabolic clearance of 3H-25-hydroxyvitamin D was prolonged when the concentration of 1,25-dihydroxyvitamin D in plasma was decreased by suppressing secondary hyperparathyroidism with large calcium supplements. In the longer-term studies (n = 10) there was a highly significant inverse relation (r = -0.88, P < 0.001) between the change in the plasma concentration of 1,25-dihydroxyvitamin D and the induced change in the elimination half-time of 3H-25-hydroxyvitamin D. There was also a significant correlation (r = 0.66, p < 0.0025) between the observed fall in the plasma concentration of unlabelled 25-hydroxyvitamin D and the predicted fall calculated from the measured value for the half-time of the 3H-labelled metabolite. In acute studies in patients with post-menopausal osteoporosis (n = 7), enhanced metabolic inactivation of 3H-25-hydroxyvitamin D was detectable within 24 hours of oral administration of 1,25-dihydroxyvitamin D.

CONCLUSIONS

The effect of 1,25-dihydroxyvitamin D on the catabolism of 25-hydroxyvitamin D can contribute to the development of vitamin D deficiency in many clinical disorders. When the natural supply of vitamin D is limited by sunlight deprivation, a sustained increase in the plasma concentration of 1,25-dihydroxyvitamin D due to primary or secondary hyperparathyroidism will lead to accelerated depletion of vitamin D stores.

Metabolic bone disease following gastrectomy: assessment by dual energy X-ray absorptiometry

Although disorders in bone metabolism have long been recognized as typical sequelae of gastrectomy, there has until now been no reliable method of providing precise assessment of bone mass, resulting in a variation of reported incidence. In this study, metabolic bone disease was evaluated in a well characterized population: 34 men 2-5 years after gastrectomy; 11 men 6-10 years after gastrectomy; eight men 2-5 years after colonic resection; and 115 healthy men. The age range was 50-69 years. An innovative reliable method of dual energy X-ray absorptiometry was used which allows quantitative assessment of bone mineral content. Measurement of lumbar spine bone mineral density revealed that the mean(s.e.m.) bone mineral density in patients who had had a gastrectomy (2-5 years 0.84(0.03) g/cm2, 6-10 years 0.85(0.05) g/cm2) was significantly lower than that of patients who had undergone colonic resection (0.96(0.04) g/cm2) or healthy men (0.96(0.03) g/cm2). This study demonstrates that a high incidence of bone atrophy is induced at the relatively early period of 2-5 years after gastrectomy.

Osteopenia and osteomalacia after gastrectomy: interrelations between biochemical markers of bone remodelling, vitamin D metabolites, and bone histomorphometry

The prevalence of metabolic disease in a population of 68 postgastrectomy patients was assessed using histomorphometric evaluation of transiliac bone biopsy specimens after tetracycline double labelling. Trabecular bone volume was significantly lower in the postgastrectomy group (p less than 0.01): 62% of the patients had increased osteoid surface, 56% increased osteoid thickness, and 24% increased mineralisation lag time. Only 18%, however, fulfilled the diagnostic criteria for osteomalacia--increased osteoid thickness and increased mineralisation lag time. Postgastrectomy patients had reduced serum concentrations of calcium (p less than 0.01), phosphate (p less than 0.01), and 25-hydroxyvitamin D, while levels of alkaline phosphatase and 1,25 dihydroxyvitamin D were high (p less than 0.01). The severity of the mineralisation defect as reflected by mineralisation lag time was positively correlated to serum 25-hydroxyvitamin D, but unrelated to serum 1,25-dihydroxyvitamin D. Multiple linear regression analysis showed that serum 25-hydroxyvitamin D, age, and the duration of postoperative follow up were significant determinants of the mineralisation defect in a given patient. The limited value of serum markers in the diagnosis of osteomalacia was emphasised by the fact that six of the eight patients with osteomalacia had normal serum levels of calcium and alkaline phosphatase, and five of the eight had values for 25-hydroxyvitamin D in the normal range for healthy control subjects. The results clearly show the need for vitamin D supplementation and regular control after gastric resection.

Importance of the stomach in maintaining calcium homoeostasis in the rat

The stomach helps to maintain calcium homoeostasis by making dietary calcium accessible for uptake in the intestines, although the effect of the stomach on calcium homoeostasis is poorly understood. We examined the effect on blood calcium of gastric surgery in the rat. Within three weeks gastrectomy and fundectomy (excision of the acid producing part of the stomach) induced a slight lowering of the blood calcium concentration. When parathyroidectomy was combined with either gastrectomy or fundectomy the blood calcium concentrations promptly dropped to values lower than after parathyroidectomy alone. The mortality was close to 100% during the first three weeks after combined parathyroidectomy and gastric surgery. It was nil in rats subjected to parathyroidectomy alone. Gastrectomised rats absorbed Ca2+ better than unoperated control rats, possibly reflecting the fact that the serum 1,25-dihydroxyvitamin D concentration was raised. Gastrectomised rats had a food intake that was about 70% of that in intact rats, and the amount of dietary calcium absorbed (net absorption per kg body weight) by the gastrectomised rats was approximately 65% of that in intact control rats. We conclude that the acid producing part of the stomach is important for calcium homoeostasis, since its removal induced lethal hypocalcaemia in parathyroidectomised rats. One possible explanation for the hypocalcaemia induced by gastrectomy is a progressive calcium deficit. In addition, the loss of calciotrophic hormones originating in the stomach may contribute.

Secondary hyperparathyroidism and osteopenia in women following gastric exclusion surgery for obesity

Gastric exclusion has been introduced as a surgical treatment for morbid obesity. We describe two women who had undergone gastric bypass for obesity with metabolic bone disease and secondary hyperparathyroidism. In one patient transiliac bone biopsy after double tetracycline labelling demonstrated histologic evidence of hyperparathyroidism with osteitis fibrosa cystica. Six additional women who had undergone gastric exclusion were evaluated. Serum phosphorus, calcium, and creatinine were normal in all but one patient who had hypocalcemia. Serum immunoreactive parathyroid hormone was elevated in seven of eight patients and urinary calcium was less than or equal to 2 mmol/d (80 mg/24 h) in 6 patients. Lumbar spine bone mineral density was 86 +/- 7 (mean +/- SE) per cent of predicted and femoral neck bone mineral density was 89 +/- 6 per cent of predicted. Women who have had gastric exclusion for obesity may develop secondary hyperparathyroidism which could result in loss of bone mass.

Partial gastrectomy and mineral metabolism: effects on gastrin-calcitonin release

Bone mineral metabolism was studied in 20 male patients, between 8 and 18 years, after surgical treatment for peptic ulcer (ten Billroth 1 and ten Billroth 2 gastrectomies) and in 16 sex- and aged-matched healthy controls. The bone mineral content was statistically reduced only in the Billroth 2 group. Serum 25(OH)D was lower in all patients, but fractional calcium absorption was similar to the control value. This may be due to increases in 1,25(OH)2D and parathyroid activity (particularly in Billroth 2). Serum osteocalcin levels and hydroxyproline excretion were higher than in the controls. A positive linear correlation emerged not only between serum 1,25(OH)2D and PTH levels but also between each of these and serum osteocalcin and urine hydroxyproline. Both PTH and calcitriol were inversely correlated with the bone mineral mass in Billroth 2, confirming a trend observed in Billroth 1. Although calcitonin values were normal, basal gastrin levels were severely impaired in all patients. In response to a mixed meal, increases in gastrin and calcitonin were significantly lower than in the controls. The calcitonin response to intravenous calcium and pentagastrin infusion was not significantly different to the controls. The percentage increase in gastrin and calcitonin responses to oral calcium correlated positively with the reduction in bone mineral content only in the Billroth 2 group, suggesting a reduction in calcitonin release may contribute to gastric surgery osteopenia in these patients.