Calcium Metabolism In Postmenopausal Women Research Articles

Фосфорно-кальцієвий обмін у постменопаузних жінок із цукровим діабетом: вплив типу та тривалості хвороби, терміну менопаузи та маси тіла

У дослідженні вивчено вплив цукрового діабету (ЦД) на фосфорно-кальцієвий обмін у жінок у постменопаузі залежно від типу та тривалості хвороби, терміну менопаузи, маси тіла та виду гіпоглікемічної терапії. Досліджено стан фосфорно-кальцієвого обміну у 86 жінок: із ЦД 1-го типу — 13 пацієнтів і ЦД 2-го типу — 73 хворих. У всіх пацієнток концентрація кальцію і фосфору в крові була в межах норми. Установлено, що концентрація іонізованого кальцію, загального кальцію та неорганічного фосфору в крові не може слугувати головним критерієм стану мінеральної щільності кісткової тканини в жінок у постменопаузі із ЦД. Препарати сульфонілсечовини та інсуліну в поєднанні з бігуанідами не впливають на стан фосфорно-кальцієвого обміну в жінок у постменопаузі із ЦД 2-го типу.

Comparative effects of denosumab or bisphosphonate treatment on bone mineral density and calcium metabolism in postmenopausal women

Aim: The aim of this retrospective follow-up study was to investigate the effect of denosumab compared with that of bisphosphonates on bone density and indices of bone metabolism in postmenopausal women.

Simvastatin Effect on Calcium and Silicon Plasma Levels in Postmenopausal Women with Osteoarthritis.

Postmenopausal women more often suffered from knee osteoarthritis and its pathogenesis still remains unclear. Calcium and silicon are significant elements involved in bone and joint metabolism, especially in older people. Cardiovascular diseases are common worldwide and simvastatin is the most prescribed drug in such population of patients. The purpose of this study was to evaluate the effect of simvastatin administration on calcium and silicon concentration in the plasma of postmenopausal women with osteoarthritis. Sixty postmenopausal mild hypercholesterolemic women (mean age 61.4 years, range 54–68) were enrolled. Thirty patients received simvastatin (20 or 40 mg/day) for at least 1 year before being enrolled (simvastatin “+” group). Control group consists of remaining 30 women (simvastatin “−“group). Silicon and calcium concentrations were measured spectrophotometrically. Plasma simvastatin level was determined 3 h after the drug administration using HPLC-UV-Vis. Calcium but not silicon level was significantly lower in patients receiving simvastatin in comparison with non-statin group (1.91 ± 0.32 vs. 2.33 ± 0.19 mmol/l, p < 0.05). A weak but significant positive correlation between plasma silicon and simvastatin levels (r = 0.3, p < 0.05) was observed; this may be due to the fact that simvastatin contains silicon dioxide as an inactive ingredient. The mean simvastatin concentration was 9.02 ng/ml. All hypotheses were verified at the significance level of p < 0.05. A statistically significant decrease in the plasma calcium concentration of postmenopausal women, treated with simvastatin suggests that simvastatin may play a role in calcium metabolism in postmenopausal women with osteoarthritis. Positive correlation of simvastatin concentration with silicon level in the plasma suggests that both might prompt the positive effect of osteoarthritis treatment.

Potassium bicarbonate supplementation and calcium metabolism in postmenopausal women: are we barking up the wrong tree?

A recent study of postmenopausal women has shown that the administration of 60-120 mmol potassium bicarbonate can neutralize net acid excretion and significantly lower urinary calcium (Ca). The changes in urinary calcium loss were sufficient to improve calcium balance and skeletal metabolism in these subjects. However, the design of the study was such that the relevance of these findings to the prevention and treatment of osteoporosis is suspect.

Sodium and Bone Health: Impact of Moderately High and Low Salt Intakes on Calcium Metabolism in Postmenopausal Women

High salt intake is a well-recognized risk factor for osteoporosis because it induces calciuria, but the effects of salt on calcium metabolism and the potential impact on bone health in postmenopausal women have not been fully characterized. This study investigated adaptive mechanisms in response to changes in salt and calcium intake in postmenopausal women. Eleven women completed a randomized cross-over trial consisting of four successive 5-wk periods of controlled dietary intervention, each separated by a minimum 4-wk washout. Moderately low and high calcium (518 versus 1284 mg) and salt (3.9 versus 11.2 g) diets, reflecting lower and upper intakes in postmenopausal women consuming a Western-style diet, were provided. Stable isotope labeling techniques were used to measure calcium absorption and excretion, compartmental modeling was undertaken to estimate bone calcium balance, and biomarkers of bone formation and resorption were measured in blood and urine. Moderately high salt intake (11.2 g/d) elicited a significant increase in urinary calcium excretion (p = 0.0008) and significantly affected bone calcium balance with the high calcium diet (p = 0.024). Efficiency of calcium absorption was higher after a period of moderately low calcium intake (p < 0.05) but was unaffected by salt intake. Salt was responsible for a significant change in bone calcium balance, from positive to negative, when consumed as part of a high calcium diet, but with a low calcium intake, the bone calcium balance was negative on both high and low salt diets.

The effect of soy protein and soy isoflavones on calcium metabolism in postmenopausal women: a randomized crossover study

Evidence suggests that soy isoflavones act as estrogen agonists and have beneficial skeletal effects, but the effects on calcium metabolism in humans are not known. This study tested whether soybean isoflavones, soy protein, or both alter calcium metabolism in postmenopausal women. Calcium metabolism in 15 postmenopausal women was studied by using metabolic balance and kinetic modeling in a randomized, crossover design of three 1-mo controlled dietary interventions: soy protein isolate enriched with isoflavones (soy-plus diet), soy protein isolate devoid of isoflavones (soy-minus diet), and a casein-whey protein isolate (control diet). There was no significant difference between the diets in net acid excretion (P = 0.12). Urinary calcium excretion was significantly (P < 0.01) less with consumption of either of the soy diets (soy-plus diet: 85 +/- 34 mg/d; soy-minus diet: 80 +/- 34 mg/d) than with consumption of the control diet (121 +/- 63 mg/d), but fractional calcium absorption was unaffected by treatment. Endogenous fecal calcium was significantly (P < 0.01) greater with consumption of the soy-minus diet than with consumption of the other diets. Total fecal calcium excretion, bone deposition and resorption, and calcium retention were not significantly affected by the dietary regimens. The lower urinary calcium seen with the consumption of an isolated soy protein than with that of an isolated milk protein was not associated with improved calcium retention. This finding reinforces the importance of evaluating all aspects of calcium metabolism. Soy isoflavones did not significantly affect calcium metabolism.

A randomized study of tibolone on bone mineral density in osteoporotic postmenopausal women with previous fractures

Objective: To investigate the effects of tibolone on trabecular and cortical bone mineral density and on indices of calcium metabolism in postmenopausal women with previous fractures. Methods: In a 2-year, randomized, double-blind, placebo-controlled, bicenter study, 45 women were treated with tibolone and 43 with placebo. All subjects received 800 mg of calcium daily. Trabecular bone mineral density of lumbar spine (L1 to L4) and cortical bone mass at the femoral neck were assessed by dual energy x-ray absorptiometry at baseline and at 6-month intervals. Serum and urinary bone biochemistry variables were also assessed. Results: After 2 years, subjects in the tibolone group gained 6.9% bone mass at lumbar spine and 4.5% at femoral neck, and respective increases from baseline in the placebo group were 2.7% and 1.4%. Tibolone-treated patients gained statistically significantly more bone mass than placebo-treated patients in the spine and femur. Urinary calcium:creatinine and hydroxyproline:creatinine ratios, as well as serum alkaline phosphatase and phosphate levels, were significantly reduced with tibolone compared with placebo. Conclusion: Tibolone induced a significant increase in trabecular (lumbar spine) and cortical (femoral neck) bone mass in postmenopausal osteoporotic women compared to placebo, suggesting its potential to treat postmeno- pausal osteoporosis.

A Randomized Study of Tibolone on Bone Mineral Density in Osteoporotic Postmenopausal Women With Previous Fractures

In Brief Objective To investigate the effects of tibolone on trabecular and cortical bone mineral density and on indices of calcium metabolism in postmenopausal women with previous fractures. Methods In a 2-year, randomized, double-blind, placebo-controlled, bicenter study, 45 women were treated with tibolone and 43 with placebo. All subjects received 800 mg of calcium daily. Trabecular bone mineral density of lumbar spine (LI to L4) and cortical bone mass at the femoral neck were assessed by dual energy x-ray absorptiometry at baseline and at 6-month intervals. Serum and urinary bone biochemistry variables were also assessed. Results After 2 years, subjects in the tibolone group gained 6.9% bone mass at lumbar spine and 4.5% at femoral neck, and respective increases from baseline in the placebo group were 2.7% and 1.4%. Tibolone-treated patients gained statistically significantly more bone mass than placebo-treated patients in the spine and femur. Urinary calcium: creatinine and hydroxyproline:creatinine ratios, as well as serum alkaline phosphatase and phosphate levels, were significantly reduced with tibolone compared with placebo. Conclusion Tibolone induced a significant increase in trabecular (lumbar spine) and cortical (femoral neck) bone mass in postmenopausal osteoporotic women compared to placebo, suggesting its potential to treat postmenopausal osteoporosis. Tibolone increases trabecular and cortical bone mineral density in women with postmenopausal osteoporosis.

The Effects of Brisk Walking on Markers of Bone and Calcium Metabolism in Postmenopausal Women

The Effects of Brisk Walking on Markers of Bone and Calcium Metabolism in Postmenopausal Women

The effects of brisk walking on markers of bone and calcium metabolism in postmenopausal women.

Weight-bearing exercise has been shown to maintain or increase bone mass in younger as well as older individuals but the mechanisms by which mechanical loading affects bone metabolism are not known in detail. Twelve postmenopausal women participated in a single bout of brisk walking (50% of VO2 max) for 90 minutes. Calciotropic hormones and markers of type I collagen formation (PICP) and degradation (ICTP) were measured before the exercise, and 1, 24, and 72 hours following the exercise. Total body bone mineral content (BMC) and density (BMD) were measured by dual energy X-ray absorptiometry (DXA). Brisk walking did not induce any significant changes in the concentrations of ionized calcium, parathyroid hormone (PTH), calcitonin, or osteocalcin. A significant increase of PICP was noted 24 and 72 hours (P < 0.01) after exertion and a significant decrease in the concentration of serum ICTP at 1 hour (P < 0.05) was followed by an increase at 72 hours (P < 0.001). There was no significant difference between the increases in the concentrations of PICP and ICTP at 72 hours. Strong inverse correlations between the basal levels of PTH and BMD (r = -0.78; P < 0.01) as well as between osteocalcin and BMD (r = -0.83; P < 0.01) were noticed. The changes in serum levels of bone collagen markers indicate an altered bone collagen turnover due to this moderate endurance exercise. The results also support the fact that serum levels of PTH as well as those of osteocalcin are associated with total body BMD in postmenopausal women.

Postprandial response of calcium metabolism in postmenopausal women to meals varying in protein level/source

The postprandial response of calcium metabolism to single meals varying in protein source and level was determined in eight postmenopausal women, age 51 to 65 years. Following an overnight fast, subjects consumed a liquid meal containing either 15 g or 45 g of protein from beef (B), cottage cheese (C), or soy isolate (S; 45 g only); one meal provided 0 g protein (basal). Blood was collected before the meal and at 30, 60, 120, and 180 minutes post-meal. Urine was collected every 30 minutes post-meal. Urinary Ca excretion significantly increased following 45-g protein meals when compared with basal meals, but not when compared with 15 g protein meals. Although glomerular filtration rate (GFR) was unaffected by diet, percent renal tubular Ca reabsorption was significantly reduced following C45 or S45 meals. No consistent changes in serum levels of parathyroid hormone (PTH) and calcitonin (Ct) were observed in response to diet. Serum phosphorus levels were significantly reduced following high-protein meals when compared with no-protein meals. Insulin response varied with protein level and source (C45 > S45 > C15 > B45 > B15 > basal). Significant associations found between insulin and calcium metabolism indicate a possible role of insulin in the mechanism of protein-induced calciuria.

Effects of oestrogen and progestogen therapy on calcium metabolism in post-menopausal women.

The effects of estrogen therapy on calcium metabolism was studied in postmenopausal women. Ethinyl estradiol gradually decreases plasma and urinary calcium and phosphate levels reaching a maximum at about 6 months. This decline is partially reversed by the end of 1 year though values consistently and indefinitely remain lower than control values. Tubular reabsorption of phosphate also shows a similar pattern. Urine calcium levels fall earlier than urine hydroxyproline though bo th appear to remain within the premonpausal range indefinitely. The hyp ophosphatalmic effect of estrogens is in part due to an inhibition of bone resorption but appears primarily due to parathyroid stimulation. The rise in calcium absorption may be explained by the rise in parathyroid hormone. Since the reduction in the rate of new bone formation is not as great as the degree of inhibition of bone resorption the net long-term effect is an enhancement of bone calcium balance. However there is no evidence that estrogens directly stimulate new bone formation. It is not certain to what extent the incidence of forearm fracture spinal osteoporosis and fractured femur of the neck might be reduced by the inhibition of bone resorption nor is it known how estrogens inhibit bone resorption. The comparative doses of estrogen needed to significantly reduce urine calcium excretion at 1 month are 6 mg estriol succinate .025 mg ethinyl estradiol .1 mg estrone sulphate and .65 mg conjugated estrogens. The results indicate that estrogens are capable of inhibiting bone resorption in postmenopausal women for most likely an indefinite period of time.