An improved method for routine determination of vitamin D and its hydroxylated metabolites in serum from children and adults

Measurement of circulating 25-hydroxyvitamin D: A historical review

The constantly increasing requests for the measurement of serum 25-hydroxyvitamin D over the last years has led reagent manufacturers to market different automated and semi-automated methods, that being unfortunately not fully harmonized, yield different results. Liquid chromatography coupled to tandem mass spectrometry (LC/MS2) has more recently been introduced. This approach allows the distinction between the two forms of 25-hydroxyvitamin D and to measure other metabolites. This approach also requires harmonization to curtail the differences between the different analytical methods. To meet this requirement, the American National Institutes of Health (NIH), the Centre for Disease Control and Prevention (CDC) in Atlanta, the National Institute of Standards and Technology (NIST) and the vitamin D Reference laboratory of Ghent University have pooled their expertise to develop a standardization program. This article reviews the main elements and the difficulties of the automated and semi-automated methods for 25-hydroxyvitamin D, from sample preparation to the analytical phase, as well as those related to mass spectrometry. It also emphasizes the need for standardization to better define the clinical decision thresholds of vitamin D nutritional status.

Different vitamin D substrate-product relationship after oral vitamin D supplementation in familial benign hypercalcemia, primary hyperparathyroidism, and healthy controls

CONTEXT

In healthy subjects and in patients with primary hyperparathyroidism (PH), the administration of a low dose of 25(OH)D (25 μg/day) increases the serum levels of both 25(OH)D and 1,25(OH)(2)D. It is unknown whether this relationship is present in patients affected by familial benign hypocalciuric hypercalcemia (FBH).

OBJECTIVE

To evaluate the different vitamin D substrate-product relationship after oral vitamin D supplementation in familial benign hypercalcemia, PH, and healthy controls.

DESIGN

We evaluated the main physiological regulators of 1α-hydroxylase and the substrate-product relationship of 25(OH)D and 1,25(OH)(2)D in 20 patients with PH, 25 with FBH, and 122 healthy sex- and age-matched controls before and after administration of 25(OH)D for 2 weeks.

RESULTS

25(OH)D increased significantly in all subjects, whereas 1,25(OH)(2)D serum levels increased significantly in PH patients and healthy controls but not in patients with FBH. Therefore, a significant positive substrate-product relationship of 25(OH)D-1,25(OH)(2)D was found in PH and healthy controls, but not in FBH. Monomeric calcitonin (hCT-M) was significantly lower at baseline and after 25(OH)D supplementation in the FBH group compared with the other two groups.

CONCLUSIONS

The lack of 1,25(OH)(2)D increase in FBH may be due to a direct inhibitory effect on 1α-hydroxylase of hypercalcemia per se, increased metabolic clearance of 1,25(OH)(2)D, or a decreased stimulus of 1α-hydroxylase related to persistently low levels of hCT.

Role of 24-hydroxylase in vitamin D3growth response of OVCAR-3 ovarian cancer cells

Vitamin D and its analogues are potent regulators of cell growth and differentiation both in vivo and in vitro. We studied the effects of 25-hydroxyvitamin D(3) [25(OH)D(3)], 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] and vitamin D analogue, EB 1089, on the growth of a human ovarian cancer cell line, OVCAR-3. We also studied the expression of vitamin D metabolising enzymes 24-hydroxylase (24OHase) and 1alpha-hydroxylase (1alphaOHase). Our results showed that high concentrations (10 and 100 nM) of 1,25(OH)(2)D(3) inhibited a cell proliferation, whereas low concentration (0.1 nM) stimulated growth of the OVCAR-3 cells. In the concentration range of 10-500 nM a prohormone, 25(OH)D(3), stimulated growth. An amount of 1 nM EB 1089 and 100 nM 1,25(OH)(2)D(3) inhibited growth with an equal magnitude. The expression of 24OHase was strongly induced by 1,25(OH)(2)D(3) and EB 1089 in OVCAR-3 cells, and analysis of vitamin D metabolites showed the functionality of 24OHase. An inhibition of 24OHase activity with a novel 24OHase inhibitor enhanced growth-inhibiting effects of 1,25(OH)(2)D(3) and suppressed the growth stimulation of 100 nM 25(OH)D(3). We also report the expression of a vitamin D activating enzyme, 1alphaOHase, in 7 ovarian cancer cell lines. The production of 1,25(OH)(2)D(3) in OVCAR-3 cells was low, possibly due to an extensive activity of 24OHase or a low 1alphaOHase activity. These results suggest that in ovarian cancer cells vitamin D metabolizing enzymes might play a key role in modulating the growth response to vitamin D. The possible mitogenic effects of vitamin D should be considered when evaluating treatment of ovarian cancer with vitamin D.

Long-term valproate and lamotrigine treatment may be a marker for reduced growth and bone mass in children with epilepsy

PURPOSE

To determine whether long-term treatment with valproate (VPA) and/or lamotrigine (LTG) in children with epilepsy is associated with altered growth and/or bone metabolism.

METHODS

Twenty-seven boys and 26 girls, aged 3 to 17 years (9.2 +/- 3.9, mean +/- SD), with epilepsy treated with VPA and/or LTG for > or =2 years were evaluated for growth, nutrient intakes, physical activity, bone mineral density (BMD), and blood biochemical indices of mineral and bone metabolism.

RESULTS

Twenty-three (43.4%) of the children had a body height below the 10th percentile. Z-scores for BMD below -1.5 occurred in 24.4% of the children. When patients were divided into two groups according to daily activity score, a significantly lower Z-score for total body BMD (p = 0.007), percentile for body height (p = 0.05), and plasma parathyroid hormone (PTH; p = 0.04), osteocalcin (p = 0.04) and 25-hydroxyvitamin D (25OHD) (p = 0.01) were found in the inactive compared with the active group. Z-score for total body BMD was correlated with daily activity score (r = 0.43, p = 0.008). Plasma intact osteocalcin and intact PTH values correlated significantly (r = 0.36, p = 0.02). Plasma 1,25-dihydroxyvitamin D was within normal range for all subjects. When patients were divided into LTG-alone, VPA-alone, and LTG-plus-VPA treatment groups, significantly lower (p < 0.05) plasma osteocalcin and percentile for body height were found in the VPA-plus-LTG treatment group.

CONCLUSIONS

Long-term VPA and LTG therapy, particularly when combined, is associated with short stature, low BMD, and reduced bone formation. These alterations may be mediated primarily through reduced physical activity rather than through a direct link to the VPA and/or LTG therapy.

Disturbance in bone turnover in children with a malignancy at completion of chemotherapy

BACKGROUND

Osteoporosis and pathological fractures have been observed in children with a malignancy. The mechanisms of osteopenia in childhood malignancies have not been well established. The purpose of the present study was to evaluate changes in bone turnover and in bone hormonal metabolism in children with a malignancy at completion of their chemotherapy.

PROCEDURE

Serum levels of human intact osteocalcin, type I collagen carboxyterminal propeptide (PICP), type I collagen carboxyterminal telopeptide (ICTP), 25-hydroxyvitamin D [25-(OH)-D], 1,25-dihydroxyvitamin D [1, 25-(OH)(2)-D], intact parathyroid hormone, insulin-like growth factor I (IGF-I), IGF binding protein 3 (IGFBP-3), alkaline phosphatase, calcium, and phosphate were analyzed in 22 children with acute lymphoblastic leukemia and in 26 children with other malignancies. Results were expressed as Z-scores [mean (95% confidence intervals)] relative to healthy Caucasian-children.

RESULTS

The marker of collagen degradation (ICTP) was significantly increased [1.43 (1.10-1.76), P < 0.0001] compared to reference values, whereas the markers of bone formation (PICP, osteocalcin) were not changed [0.07 (-0.55 to 0.49), 0.35 (-0.05 to 0.74), respectively, NS]. Serum 25-(OH)-D, 1,25-(OH)(2)-D, and calcium were significantly reduced [-0.65 (-0.87 to -0.42), -0.68 (-0.92 to -0. 42), -1.42 (-1.80 to -1.04), P < 0.0001, respectively].

CONCLUSIONS

Disturbance in bone turnover with low serum 25-(OH)-D, 1, 25-(OH)(2)-D, and calcium was observed in children with a malignancy at completion of their chemotherapy. A controlled study determining the possible benefits of vitamin D and calcium supplementation on bone turnover could be considered in these patients.

The long-term effect of early mineral, vitamin D, and breast milk intake on bone mineral status in 9- to 11-year-old children born prematurely

BACKGROUND

Although the short-term benefits of mineral supplementation in preterm infants has been established, the long-term benefits are less clear. The purpose of the study was to evaluate effects of early-life mineral, vitamin D, and breast milk intake on bone mineral status in children 9 to 11 years of age who were born prematurely.

METHODS

Seventy preterm infants born 1985 through 1987 were randomized into four groups: to receive a vitamin D dose of 500 or 1000 IU/day and calcium- and phosphorus-supplemented or unsupplemented breast milk. At 3 months of age, radial bone mineral content was determined by single-photon absorptiometry and vitamin D metabolites were assessed. At 9 to 11 years of age, the bone mineral status of the radius and lumbar spine was assessed using dual energy x-ray absorptiometry.

RESULTS

At the age of 3 months, the preterm infants with diets supplemented with minerals had 36% higher bone mineral content than the preterm infants whose diet was not supplemented with minerals. At the age of 9 to 11 years, in contrast, bone mineral status was comparable among the groups, irrespective of different mineral supplementation during the neonatal period. Interestingly, the lumbar bone mineral apparent density was positively related to lactation in mineral-supplemented children. There was neither short-term nor long-term benefit to bone mineral status of a vitamin D dose of 1000 IU/day compared with 500 IU/day.

CONCLUSIONS

The short-term benefit to bone mineral density in preterm infants of mineral supplementation of the early diet is obvious, but, in the long term, the effects seem to disappear. The results also imply that a relatively long period of breast-feeding may be needed to optimize long-term bone mineral acquisition in the lumbar spine.

Randomised controlled trial of vitamin D supplementation on bone density and biochemical indices in preterm infants

AIMS

To test the hypothesis that a vitamin D dose of 200 IU/kg, maximum 400 IU/day, given to preterm infants will maintain normal vitamin D status and will result in as high a bone mineral density as that attained with the recommended dose of 960 IU/day.

METHODS

Thirty nine infants of fewer than 33 weeks of gestational age were randomly allocated to receive vitamin D 200 IU/kg of body weight/day up to a maximum of 400 IU/day or 960 IU/day until 3 months old. Vitamin D metabolites, bone mineral content and density were determined by dual energy x-ray absorptiometry, and plasma ionised calcium, plasma alkaline phosphatase, and intact parahormone measurements were used to evaluate outcomes.

RESULTS

The 25 hydroxy vitamin D concentrations tended to be higher in infants receiving 960 IU/day, but the differences did not reach significance at any age. There was no difference between the infants receiving low or high vitamin D dose in bone mineral content nor in bone mineral density at 3 and 6 months corrected age, even after taking potential risk factors into account.

CONCLUSIONS

A vitamin D dose of 200 IU/kg of body weight/day up to a maximum of 400 IU/day maintains normal vitamin D status and as good a bone mineral accretion as the previously recommended higher dose of 960 IU/day. Vitamin D is a potent hormone which affects organs other than bone and should not be given in excess to preterm infants.

Reduced bone mineral density in long-term survivors of childhood acute lymphoblastic leukemia

PURPOSE

Osteoporosis and pathologic fractures are occasionally found in patients with childhood acute lymphoblastic leukemia (ALL). This study was performed to determine the degree of possible osteopenia in long-term survivors of childhood ALL.

PATIENTS AND METHODS

Lumbar spine (L2-L4) and femoral neck bone mineral densities (BMDs) (g/cm2) were measured in 29 survivors (aged 12 to 30 years, median 17) of childhood ALL 2 to 20 (median 8) years after discontinuation of chemotherapy. These results were compared with those from 273 healthy controls and expressed as a percentage of the age- and sex-matched control values (mean +/- standard deviation).

RESULTS

Lumbar and femoral BMDs were significantly reduced in survivors of childhood ALL. Particularly, male gender (lumbar: 91.7 +/- 10.4%, p = 0.008; femoral: 91.9 +/- 11.3%, p = 0.005) and a history of cranial irradiation (lumbar: 93.0 +/- 8.9%, p = 0.005; femoral: 94.4 +/- 13.3%, p = 0.03) were associated with low lumbar and femoral BMDs.

CONCLUSIONS

The detected deficit in bone density in survivors of childhood ALL may predispose these patients to osteoporotic fractures later in adulthood. A follow-up of BMD in survivors of childhood ALL should facilitate the identification of patients who would require specific therapeutic interventions to prevent further decrease of their skeletal mass and preserve their BMD.

Biochemical bone markers and bone mineral density during postmenopausal hormone replacement therapy with and without vitamin D3: a prospective, controlled, randomized study

The effects of postmenopausal hormone replacement therapy (HRT) and vitamin D on the serum concentrations of three bone biochemical markers and their associations with bone mineral density (BMD) were studied in a population-based 1-yr follow-up study. A total of 72 healthy postmenopausal women were randomized into 4 treatment groups: HRT group (sequential combination of 2 mg estradiol valerate and 1 mg cyproterone acetate), D group (vitamin D3, 300 IU/day), HRT+D group (both of the above), and placebo group (calcium lactate, 500 mg/day). Serum concentrations of osteocalcin (OC) and bone-specific alkaline phosphatase (BAP) were measured as biochemical markers of bone formation, and serum type I collagen carboxy-terminal telopeptide was measured as a marker of bone resorption at baseline and after 6 and 12 months of treatment. To investigate the associations of these markers with BMD, lumbar (L2-L4) and femoral neck BMDs were determined by dual x-ray absorptiometry at baseline and after 2.5 yr of treatment. In both hormone groups, the serum concentrations of the three bone metabolic markers had decreased after 12 months. Those of OC decreased by 29.2% (P = 0.017) in the HRT group and by 37.3% (P = 0.004) in the HRT+D group, and BAP concentrations decreased by 34.4% (P < 0.001) in the HRT group and by 36.2% (P < 0.001) in the HRT+D group. Serum type I collagen carboxy-terminal telopeptide concentrations had decreased by 21.6% (P = 0.012) in HRT group and by 14.1% (P = 0.011) in the HRT+D group. In the D group, the serum concentrations of BAP had decreased by 11.7% (P = 0.040) after 12 months, but the other two markers showed no change. The only change seen in the placebo group was a 19.2% increase in OC concentrations (P = 0.041) after 6 months, but at 12 months, the mean OC level was similar to that at baseline. After 2.5 yr, both lumbar and femoral BMD had decreased in the D group [2.1% (P = 0.022) and 3.6% (P = 0.019), respectively] and in the placebo group [3.3% (P = 0.009) and 2.7% (P = 0.010), respectively], whereas no significant changes occurred in the hormone groups. There were significant inverse correlations between the changes in lumbar and femoral BMDs and changes in all three biochemical markers (r = -0.240 through -0.336; P = 0.005-0.064). Our results suggest that HRT counteracts the biochemical changes caused by increased bone turnover associated with menopause. Importantly, the changes in bone markers correlate with long term changes in BMDs of lumbar spine and femoral neck. Low dose vitamin D treatment, however, seems to have only marginal effects on bone metabolism in early postmenopausal healthy women.

Alphacalcidol oral pulses normalize uremic hyperparathyroidism prior to dialysis

Alphacalcidol oral pulse therapy was given for secondary hyperparathyroidism to 22 children (mean age of 5.6 years) with renal insufficiency. At the beginning of the study, the glomerular filtration rate was < 50% of normal, serum intact parathyroid hormone (PTH) was > 100 ng/l and the serum phosphate and calcium concentrations were within the normal range. Alphacalcidol (0.5-3.0 micrograms) was given orally thrice weekly in the evening and adjusted according to PTH, ionized calcium and phosphate concentrations. Serum PTH (mean +/- SEM) decreased significantly from a pre-treatment level of 393 +/- 81 ng/l to 122 +/- 34 ng/l after 12 months, and stabilized at this level. Mean vitamin D metabolite concentrations were within the normal range. 1,25-Dihydroxyvitamin D did not increase during therapy, while PTH decreased. The estimated creatinine clearance remained almost unchanged (20 +/- 3 and 21 +/- 6 ml/min per 1.73 m2). Growth remained low normal (height standard deviation score -1.8 +/- 0.3 initially and -1.7 +/- 0.4 12 months later) and bone mineral density did not decrease. We concluded that feedback regulation of PTH with oral alphacalcidol pulse therapy is effective in the treatment of hyperparathyroidism in children with renal failure prior to dialysis.

Intraplatelet free calcium and calcium-regulating hormones in plasma are not related to the antihypertensive effect of nifedipine in hypertensive pregnancy

Intracellular free calcium regulates contraction-relaxation processes in vascular smooth muscle. We compared intraplatelet free calcium ([Ca2+]i) and pH ([pH]i) in hypertensive pregnant women to those in normotensive pregnant and non-pregnant women. Plasma parathormone and vitamin D metabolite were simultaneously assessed. In hypertensive pregnancy, [Ca2+]i tended to be lower than in normotensive pregnant (P = 0.08) and non-pregnant subjects (P = 0.06). In hypertensive pregnancy, 1,25, (OH)2 vitamin D in plasma was in the same range as in non-pregnant women and significantly lower than in normotensive pregnancy (p < 0.01). The other two vitamin D metabolites, parathormone and [pH]i were equal in the three groups. A five-day nifedipine treatment (10 mg t.i.d.) increased [Ca2+]i in hypertensive pregnant (P < 0.05) and normotensive non-pregnant subjects (P = 0.06), whereas [pH]i (P < 0.05) and 25 (OH) vitamin D (P < 0.05) decreased in the former and 24,25 (OH)2 vitamin D increased in the latter group (P < 0.05). Initial [Ca2+]i did not correlate with blood pressure in any group. The antihypertensive effect of nifedipine did not correlate with any variable measured. In conclusion, [Ca2+]i and calcium-regulating hormones seem not to be related to the antihypertensive effect of nifedipine in hypertensive pregnancy. In this type of hypertension, intraplatelet calcium may not reflect calcium balance in smooth muscle cells regulating vascular tone and blood pressure.

Does vitamin D3 have negative effects on serum levels of lipids? A follow-up study with a sequential combination of estradiol valerate and cyproterone acetate and/or vitamin D3

The effects of four different treatment schedules on serum lipid concentrations were studied for 1 year in 402 postmenopausal women in the Kuopio Osteoporosis Study. The women were randomized to four treatment groups: A, Sequential combination of estradiol valerate and cyproterone acetate (Climen); B, Vitamin D3, 300 IU/day; C, Climen+Vitamin D3, D, placebo. In group A, serum concentrations of total cholesterol (Chol) decreased by 4.8% in 6 months and by 6.2% in 12 months (P < 0.001), but in group C the decrease was only 2.9% in 6 months (P < 0.05) and 3.4% in 12 months (P < 0.01). The decline of total-Chol in group A was accounted for by the 6.8% to 7.5% decrease in LDL-Chol levels (P < 0.001). The decrease of LDL-Chol in group C was statistically non-significant. Use of vitamin D3 (group B), increased serum Chol by 2.7% (6 months), P < 0.05 and by 2.1% (12 months) and the increases were the result of the 6.0% to 6.2% increase in LDL-Chol levels in 6 and 12 months, respectively (P < 0.001). Serum concentrations of HDL-Chol and TG remained relatively stable in all groups. No correlations were found between LDL-Chol, 25-OH-D3 and 1,25(OH)2-D3 levels in group B. Our results confirm the beneficial effect of estradiol valerate and cyproterone acetate on the lipid profile. In contrast, vitamin D3 had a negative influence on this profile by increasing serum concentrations of LDL-Chol.(ABSTRACT TRUNCATED AT 250 WORDS)

Two-site enzyme immunoassay for measuring intact human osteocalcin in serum

We developed a sensitive two-site sandwich ELISA for quantitative analysis of human osteocalcin in serum or plasma. Our method is based on two different highly specific antibodies recognizing epitopes at different ends of the protein so that only intact osteocalcin is detected. The method is fast (total analysis time less than 6 h/96 wells), precise (intraassay variation less than 2.3% at four different levels; n = 10, and interassay variation less than 2.5%, n = 5, respectively), and accurate, with a mean recovery of 105%. The detection limit in serum is approximately 0.1 micrograms/liter. The mean concentration of osteocalcin in normal serum with this assay is 3.3 micrograms/liter (SD 3.7 micrograms/liter; range 0.1-13.1 micrograms/liter; n = 41), and the reference range is 0.28-10.1 micrograms/liter (10 and 90% confidence limits). The method shows a reasonable positive linear correlation with other osteocalcin assays (Incstar, r = 0.55, p < 0.05, n = 13; Henning Oscatest, r = 0.52, p < 0.005, n = 34). A good correlation (r = 0.70, p < 0.001) between individual osteocalcin and bone-specific alkaline phosphatase serum concentrations was observed in normal subjects. We found a low or undetectable concentration of intact osteocalcin in serum of all four of our patients with acute primary hyperparathyroidism, and in all five patients with hypocalcemic secondary hyperparathyroidism, which suggests that PTH effectively inhibited the synthesis of osteocalcin in osteoblasts. The serum concentration of intact osteocalcin was elevated in two of three patients with chronic primary hyperparathyroidism.(ABSTRACT TRUNCATED AT 250 WORDS)

Scintillation proximity assay for calcitriol in serum without high pressure liquid chromatography

A rapid isolation step for 1,25-dihydroxyvitamin D3 without high pressure liquid chromatography (HPLC) and a sensitive radioimmunoassay (RIA) have been developed. The time required for extraction and isolation with a combination of Extrelut-1-minicolumns and Sep-Pak silica cartridges from as little as 0.5 ml serum is only 2 h. The assay can be counted after 8 h of incubation. It is performed in the vial that collects the eluate, thus eliminating transfer losses and errors. No separation of bound and free hormone is necessary before beta-counting in the scintillation proximity assay. The detection limit of the assay is 2.7 ng/l. The intra-assay coefficients of variation are 7.3% and 5.2% for samples with calcitriol concentrations of 31 and 148 ng/l, respectively. The inter-assay coefficients of variation are 11.3%, 13.3% and 16.1% for low (16 ng/l), medium (30 ng/l) and high (148 ng/l) control pool samples, respectively. Normal values for calcitriol range from 32 to 80 ng/l. Elderly subjects, patients with reduced kidney function and pregnant women were also evaluated for their calcitriol levels. This assay correlates well with a RIA employing HPLC prepurification and charcoal separation of bound/free calcitriol (r = 0.94).

Low serum vitamin D metabolites in women with rheumatoid arthritis

The etiology of osteoporosis associated with rheumatoid arthritis (RA) is unknown. We studied the calcium and vitamin D metabolism in 143 women with RA (mean age 50.7 years). Albumin corrected serum calcium was normal. Serum alkaline phosphatase was increased in 29 percent of cases. Serum vitamin D levels were frequently very low. In 16 percent of the RA patients serum 25(OH)D concentration was below 12.5 nmol/L, which is arbitrarily considered as the limit of vitamin D deficiency osteomalacia. In the winter season 73 percent of the patients had serum 1,25(OH)2D levels below the seasonally adjusted normal range. The lowest values were found in patients with high disease activity. We suggest that there is a disturbance in vitamin D metabolism in RA. This might play a role in osteoporosis associated with RA.

Annual injection of vitamin D and fractures of aged bones

In order to investigate the effect of a supplementation of vitamin D in the prophylaxis of fractures of the bones of aged people, an annual intramuscular injection of ergocalciferol (150,000-300,000 IU) was given to two series of aged subjects: first to 199 (45 male) of 479 subjects (110 male) aged more than 85 years who were living in their own home, and second to 142 (29 male) of 320 (58 male) subjects aged 75-84 and living in a home for aged people. This prospective series was divided into treatment groups according to month of birth. These injections were given annually from September to December in the years 1985-1989, two to five times to each participant. The fracture rates, laboratory values, vitamin D levels, possible side effects, and mortality were followed until October 1990. A total of 56 fractures occurred in the 341 vitamin D recipients (16.4%) and 100 in 458 controls (21.8%) (P = 0.034). The fracture rate was about the same in both outpatient and municipal home series. Fractures of the upper limb were fewer in the vitamin D recipients, 10/341 = 2.9% (P = 0.025), than in the controls, 28/458 = 6.1%, during the follow-up. A similar result was obtained in fractures of ribs, 3/341 = 0.9% and 12/458 = 2.6%, respectively. Fractures of the lower limbs occurred almost as frequently, 31/341 = 9.1%, among the vitamin D recipients as among the controls, 49/458 = 10.7%. The fracture rate was higher in females (22.2%) than in males (9.5%). The fractures were fewer in the vitamin D recipients only in females.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of calcitonin on bone histomorphometry and bone metabolism in rheumatoid arthritis

Twenty-four women (mean age +/- SD 49 +/- 13 years) with classical or definite rheumatoid arthritis (disease duration 15 +/- 8 years) were treated with synthetic salmon calcitonin (SCT) nasal spray 200 IU three times a week for 3 months. Bone biopsies from the iliac crest were taken before and after SCT treatment. Histomorphometrical quantification of undecalcified bone sections was made using the manual point-counting method. SCT decreased the resorption surface of trabecular bone (ES/BS) significantly (P less than 0.001). There was also a significant increase (P less than 0.05) in trabecular bone volume (BV/TV) after 3 months of treatment, whereas no statistically significant changes were found in osteoid parameters. There were no significant changes in biochemical analyses of bone metabolism. We conclude that SCT might be useful in the prevention of bone loss in RA.

The necessity and safety of calcium and vitamin D in the elderly

The necessity and safety of an oral calcium (Ca) and vitamin D regimen was evaluated in a population of 66 independently living and 73 institutionalized elderly women over an 11-week winter period. The members of both groups were randomly assigned into trial and control groups. Serum Ca, creatinine, and calcidiol levels were measured before and after the trial. The regimen consisted of 1.558 g of Ca and 45 micrograms (equal to 1,800 IU) of vitamin D administered daily in addition to the normal diet. The controls received no treatment. A majority of the elderly subjects living independently had ensured their Ca, and a quarter of them also their vitamin D intake on their own initiative. The mean serum calcidiol concentration before the trial was 24.1 nmol/L in the institutionalized and 38.5 nmol/L in the elderly subjects living independently (P less than .001). After the trial, serum calcidiol was 10.4 nmol/L in the institutionalized control subjects and had decreased (P less than .001) in both control groups, but increased (P less than .001) in both treatment groups. The safety indicators, serum Ca, creatinine, and calcidiol, did not indicate any group or individual side effect.

Evidence suggesting hyperoxaluria as a cause of nephrocalcinosis in phosphate-treated hypophosphataemic rickets

Urinary excretion of oxalate and phosphate was measured in twelve vitamin-D-treated, phosphate-supplemented patients with X-linked hypophosphataemia (XLH; four children, eight adolescents and adults) to investigate possible causative factors of nephrocalcinosis other than calcium. Oxalate excretion correlated highly with urinary phosphate excretion and with intake of phosphate supplements corrected for body surface area. Young children received the highest relative doses of phosphate (range 2.27-10.8 g/1.73 m2 daily) and their urinary oxalate excretion was very high (0.94-3.38 mmol/1.73 m2 daily). The urinary oxalate excretion of untreated adults with XLH was within normal limits. Six patients had evidence of nephrocalcinosis on ultrasound. The high urinary oxalate excretion in phosphate-supplemented XLH may be seen as a special type of enteric hyperoxaluria, in which the conditions of calcium-oxalate crystal precipitation could be reached even at normal levels of urinary calcium excretion. Urinary excretion of both calcium and oxalate should therefore be monitored during treatment in young XLH patients.

Serum vitamin D metabolites in cadmium-exposed persons with renal damage

Serum concentrations of 25-hydroxyvitamin D [25(OH)D], 24,25-dihydroxyvitamin D [24,25(OH)2D], and 1 alpha,25-dihydroxyvitamin D [1 alpha,25(OH)2D] were measured in ten cadmium (Cd)-exposed subjects and five non exposed subjects. The Cd-exposed subjects were divided into two groups according to serum 1 alpha,25(OH)2D levels. No significant differences for 25(OH)D were found between the Cd-exposed group with low or normal serum 1 alpha,25(OH)2D and the non exposed group. The concentrations of 24,25(OH)2D were the lowest in the Cd-exposed group with low serum 1 alpha,25(OH)2D, highest in the non exposed group, and significantly lower in the Cd-exposed group with normal serum 1 alpha,25(OH)2D than in the non exposed group. Renal function was much worse in the Cd-exposed group with low serum 1 alpha,25(OH)2D than in the group with normal serum 1 alpha,25(OH)2D. These findings indicate that Cd initially disturbs hydroxylation from 25(OH)D to 24,25(OH)2D and then disturbs hydroxylation from 25(OH)D to 1 alpha,25(OH)2D. The decrease of serum 24,25(OH)2D and 1 alpha,25(OH)2D in Cd-exposed subjects is not due to a decrease of the serum 25(OH)D level.

Serum vitamin D metabolite concentrations in primary hyperparathyroidism

Forty-nine patients with primary hyperparathyroidism were examined preoperatively and three months after parathyroid operation for their serum vitamin D metabolites and routine laboratory samples related to calcium metabolism. The preoperative serum 24,25-dihydroxyvitamin D level, mean (SE) was 1.86 (0.22) nmol/l and the postoperative level 5.35 (0.63) nmol/l, the difference being highly significant (P less than 0.001). Serum 1,25-dihydroxyvitamin D levels fell significantly (P less than 0.001) from a preoperative level of 175.5 (17.9) pmol/l to 102.8 (10.1) pmol/l postoperatively. The preoperative 25-hydroxyvitamin D level did not change significantly after surgery. The preoperative serum 24,25-dihydroxyvitamin D level was very low, especially in patients with bone disease while serum parathormone was significantly higher than in patients without bone disease.

Activated charcoal in the treatment of hypercholesterolaemia: dose-response relationships and comparison with cholestyramine

The dose-response relationship of activated charcoal in reducing serum cholesterol was determined and the effects of charcoal and cholestyramine were compared in patients with hypercholesterolaemia. In a cross-over study 7 patients ingested charcoal 4, 8, 16 or 32 g/day, and finally bran, each phase lasting for 3 weeks. Serum total and LDL-cholesterol were decreased (maximum 29% and 41%, respectively) and the ratio of HDL/LDL-cholesterol was increased (maximum 121%) by charcoal in a dose dependent manner. Ten further patients with severe hypercholesterolaemia ingested daily for 3 weeks, in random order, activated charcoal 16 g, cholestyramine 16 g, activated charcoal 8 g + cholestyramine 8 g, or bran. The concentrations of total and LDL-cholesterol were reduced by charcoal (23% and 29%, respectively), cholestyramine (31% and 39%) and their combination (30% and 38%). The ratio of HDL/LDL-cholesterol was increased from 0.13 to 0.23 by charcoal, to 0.29 by cholestyramine, and to 0.25 by their combination. Serum triglycerides were increased by cholestyramine but not by charcoal. Other parameters, including the serum concentrations of vitamin A, E and 25(OH)D3 remained unaffected. The changes in lipids only partly subsided during the 3-week bran phase. In general, the acceptability by the patients and the efficacy of activated charcoal, cholestyramine and their combination were about equal, but there were individual preferences for particular treatments.

Chromatography of fat-soluble vitamins in clinical chemistry

A review is presented of current gas and liquid chromatographic methods for the determination of the fat-soluble vitamins A, D, E and K and the provitamin A beta-carotene in biological samples of human origin. For each vitamin, the discussion successively focuses on procedures for sample preparation, gas and liquid chromatographic systems and principles of detection. The emphasis is on liquid chromatography, which is gradually becoming a standard technique in fat-soluble vitamin assays. New trends in the liquid chromatography of these compounds include the use of smaller particles and shorter columns, to improve speed, and the advance of electrochemical detection as an alternative to absorbance and fluorescence detection. Bonded phases, both normal and reversed phase, tend to be preferred over underivatized silica as column supports. Gas chromatography remains of particular value in combination with mass spectrometry, a technique which may form the basis of reference methods. In general, despite the availability of well established analytical methods for fat-soluble vitamins, the wealth of recent literature in this area indicates that there continues to be a need for new assays with enhanced speed, specificity and sensitivity.

Vitamin D deficiency in women with femoral neck fracture

Calcium (Ca) metabolism, with particular reference to serum vitamin D metabolites, was investigated in 40 women with femoral neck fracture (mean age 77.1 +/- 8.6 yr). All the patients were ambulant before the fracture; eight were long-term geriatric in-patients. Serum total and ionised calcium and serum albumin levels were significantly lower, and serum parathormone (PTH) levels significantly higher in fracture patients than in controls. Both serum 25-OH-D and 1,25-(OH)2D were significantly lower in fracture patients than in controls. We concluded that vitamin D, serum PTH and calcium levels should be checked with greater frequency in patients at high risk for osteoporosis and osteomalacia before they reach the age of 70.

Vitamin D and mineral metabolism in intrahepatic cholestasis of pregnancy

Serum concentrations of 25(OH)D, 24,25(OH)2D, 1,25(OH)2D, total protein, calcium, phosphorus, magnesium and alkaline phosphatase were measured in patients with intrahepatic cholestasis of pregnancy and in control subjects at the third trimester of pregnancy and at delivery. 25(OH)D levels of 40.5 +/- 21.5 nmol/l in the patient group were initially significantly (P less than 0.01) higher than the value of 26.3 +/- 9.5 nmol/l in the control group and decreased significantly (P less than 0.01) to 26.0 +/- 16.3 nmol/l at delivery. The levels of active 1,25(OH)2D and inactive 24,25(OH)2D did not alter in either group. Also the concentrations of calcium, phosphorus and magnesium remained unchanged in both groups. No significant differences in fetal vitamin D metabolites were observed between patients and controls, and the other analysed fetal parameters were similar in both groups. Cholestyramine and/or phenobarbital treatment had no influence on vitamin D metabolites. Since levels of 1,25(OH)2D and mineral parameters remained normal and a change in 25(OH)D concentrations was only transient, the clinical role of 25(OH)D variations cannot be substantial.

Can the fetus regulate its calcium uptake?

To investigate the role of the fetus in vitamin D metabolism concentrations of vitamin D metabolites, 25(OH)D, 24,25(OH)2D and 1,25(OH)2D, were measured in human umbilical artery and vein. There were no differences between artery and vein in 25(OH)D and 24,25(OH)2D levels. 1,25(OH)2D concentrations were statistically significantly higher in the artery than in the vein. It has been shown in animal experiments that 1,25(OH)2D is an important factor in the maintenance of the placental calcium gradient. We suggest that the fetus actively produces 1,25(OH)2D and hence has the capacity to control its calcium influx.

Serum 25-hydroxyvitamin D levels in Finnish children aged 2 to 17 years

Serum levels of 25-hydroxyvitamin D (25-OHD) in summer and winter were studied in 564 children aged 2-17 years living in the northern, central or southern parts of Finland. The mean levels of 25-OHD were significantly lower in winter (13.3 +/- 10.8 ng/ml) than in summer (27.2 +/- 10.3 ng/ml) in all age groups (p less than 0.001). The mean 25-OHD levels in the northern part of the country did not differ significantly from the others. In both seasons the levels of 25-OHD were lower in the 11-17 year age group than in younger children. In that age group 22.4% of the children had serum levels of 25-OHD below 5 ng/ml (the limit of risk for rickets), compared to 16.8% of children 6-10 years old and 7.5% of children 2-5 years old, but none of the children showed any laboratory evidence of rickets.

Vitamin D metabolism in preterm infants. Serial serum calcitriol values during the first four days of life

In order to evaluate after birth the changes in circulating vitamin D metabolite levels in preterm babies supplemented with vitamin D (2 100 I.U./d), the serum concentration of 25-hydroxyvitamin D [25-OHD] and 1 alpha,25-dihydroxyvitamin D [1,25(OH)2D] were measured in 22 infants (31 to 35 weeks of gestation) from birth up to 96 hours of age. Compared to cord blood levels, serum calcium decreased significantly during the first 24 hours of life (p less than 0.005) and remained low until day 4. Serum immunoreactive parathyroid hormone (iPTH) levels increased from birth to 24 hours and then plateaued. The 25-OHD levels at birth were 27.5 +/- 2.5 nmol/l and increased to 67.5 +/- 12.5 nmol/l (p less than 0.005) during the four days of the study. During the same period, the 1,25(OH)2D serum levels increased steadily from 84 less than 7 to 343 less than 105 pmol/l (p less than 0.005). At all times, there was a positive correlation between 25-OHD levels and those of 1,25(OH)2D. Our data demonstrate that in preterm infants after 31 weeks of gestation, absorption and activation of vitamin D is present as soon as 24 hours after birth and that early neonatal hypocalcemia is unlikely to be caused by an impairment of either PTH secretion or vitamin D activation.

A simple and sensitive assay for 25-hydroxyvitamin D, 24,25-dihydroxyvitamin D and 1,25-dihydroxyvitamin D in human serum

An improved method is described which permits the simultaneous determination of 25-hydroxyvitamin D [25-(OH)D], 24,25-dihydroxyvitamin D [24,25-(OH)2D] and 1,25-dihydroxyvitamin D [1,25-(OH)2D] in milliliters of human serum. Methodological improvements enabled a rapid and almost complete extraction of the three metabolites from serum and omission of adding labeled internal standards to each serum sample for the calculation of individual recoveries. Commercially available stable chick embryo intestinal mucosa cytosol preparation made the troublesome preparation of cytosol receptor for 1,25-(OH)2D unnecessary. The procedure involves saturation of serum with ammonium carbonate and extraction with methanol/ethyl acetate, followed by separation of 25-(OH) D from the dihydroxy metabolites of vitamin D by Sephadex LH-20 column chromatography and further separation of the dihydroxy metabolites into 24,25-(OH)2D and 1,25-(OH)2D by high-pressure liquid chromatography. This is followed by individual determination of each metabolite by competitive protein-binding assay or radioreceptor assay.