Measurement of 25-hydroxyvitamin D3 and 25-hydroxyvitamin D2 in clinical settings

Vitamin D Deficiency and Its Health Consequences in Africa

Africa is heterogeneous in latitude, geography, climate, food availability, religious and cultural practices, and skin pigmentation. It is expected, therefore, that prevalence of vitamin D deficiency varies widely, in line with influences on skin exposure to UVB sunshine. Furthermore, low calcium intakes and heavy burden of infectious disease common in many countries may increase vitamin D utilization and turnover. Studies of plasma 25OHD concentration indicate a spectrum from clinical deficiency to values at the high end of the physiological range; however, data are limited. Representative studies of status in different countries, using comparable analytical techniques, and of relationships between vitamin D status and risk of infectious and chronic diseases relevant to the African context are needed. Public health measures to secure vitamin D adequacy cannot encompass the whole continent and need to be developed locally.

Low bone mineral density in Crohn's disease, but not in ulcerative colitis, at diagnosis

BACKGROUND/AIMS

The pathogenesis of low bone mineral density in patients with inflammatory bowel disease is unclear, and the relevance of secondary osteopenic influences is controversial. Our aim was to study bone mineral density in newly diagnosed patients.

METHODS

Bone mineral density and biochemical parameters of bone metabolism were measured in 15 patients with Crohn's disease and 15 patients with ulcerative colitis, all of whom were newly diagnosed. Lumbar and forearm bone mineral densities were measured by dual energy x-ray absorptiometry, and Z scores were obtained by comparison with age- and sex-matched normal values. Twenty-three patients had repeat measurements 1 year later, and 20 had received systemic steroids.

RESULTS

At diagnosis, the mean Z score for patients with Crohn's disease (spine, -1.06 +/- 0.86; forearm, -1.04 +/- 0.86) was significantly lower than that for patients with ulcerative colitis (spine, -0.03 +/- 1.16; forearm, 0.11 +/- 1.24). Inflammatory activity, disease localization, body mass index, smoking habits, sex, physical activity, or biochemical parameters did not account for this difference. Spine and forearm Z scores were significantly correlated. Mean Z scores after 1 year were not significantly different from initial Z scores.

CONCLUSIONS

At diagnosis, low bone mineralization is a feature of Crohn's disease but not ulcerative colitis. Treatment with corticosteroids did not result in further bone loss in 1 year.

Bone turnover in asthmatic children treated with oral prednisolone or inhaled budesonide

Biochemical markers of bone turnover were studied in prepubertal school children with asthma in two randomized double-blind crossover trials with run-in, treatment, and wash-out periods of 2 weeks. One group (n = 11) was treated with 2.5 and 5.0 mg prednisolone, the other (n = 14) with 200 and 800 micrograms inhaled budesonide per day. Serum osteocalcin, serum total alkaline phosphatase, fasting urinary excretion of hydroxyproline and calcium, serum 25-hydroxyvitamin D, and 1,25 dihydroxyvitamin D were assessed. A dose-related reduction of serum osteocalcin (Page's test for trend: P = 0.04; z = -2.3) and of the fasting urinary hydroxyproline:creatinine ratio (Page's test for trend: P = 0.05; z = -2.0) was found in the children who were treated with prednisolone. Inhaled budesonide was not associated with statistically significant effects on any of the biochemical markers. Short-term treatment with low daily doses of prednisolone may cause a suppression of bone turnover in children with asthma. To reduce the risk of adverse effects on bone turnover, doses of inhaled budesonide up to 800 micrograms daily may be preferable to low doses of prednisolone. Bone turnover remains to be evaluated during long-term treatment.

Comparison of vitamin D metabolism in early healthy and late osteoporotic postmenopausal women

We studied 20 healthy premenopausal women aged 36.5 +/- 4.0 years (mean +/- 1 SD), 123 healthy postmenopausal women aged 50.0 +/- 2.4 years, and 103 postmenopausal women aged 65.1 +/- 5.6 years with symptomatic osteoporosis (forearm and spinal fracture). Serum levels of vitamin D metabolites [25(OH)D, 24,25(OH)2D3, and 1,25-(OH)2D] were compared with (1) bone mass in the forearm (single photon absorptiometry) and in the spine (dual photon absorptiometry); (2) biochemical indices of bone formation (serum alkaline phosphatase, plasma bone Gla protein), and bone resorption (fasting urinary hydroxyproline); and (3) other biochemical estimates of calcium metabolism (serum calcium, serum phosphate, 24-hour urinary calcium, intestinal absorption of calcium). The present study revealed no difference in any of the vitamin D metabolites between the premenopausal women, the healthy postmenopausal women and the osteoporotic women as a group. The concentrations of 1,25(OH)2D and 25(OH)D were significantly lower in patients with spinal fracture than in those with forearm fracture. In the early postmenopausal women serum 1,25(OH)D was related to forearm bone mass (r = -0.20; P less than 0.05), intestinal calcium absorption (r = 0.18; P less than 0.05), and 24-hour urinary calcium (r = 0.21; P less than 0.05); serum 25(OH)D was related to spinal bone mass (r = 0.23; P less than 0.01). In the osteoporotic women, serum vitamin D metabolites were not related to bone mass, but 1,25(OH)2D was related to bone Gla protein (r = 0.33; P less than 0.001), serum phosphate (r = -0.27; P less than 0.01), and 24-hour urinary calcium (r = 0.43; P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Vitamin D metabolites--relation to age, menopause and endometriosis

We investigated the influence of menopause, age and sex on vitamin D metabolism in a large group of healthy women (n = 113) and men (n = 108) and in a group of early postmenopausal women (n = 124). Furthermore, we studied the vitamin D metabolism in 42 women with endometriosis. The vitamin D metabolites did not show dependence on age or on duration of menopause. The serum concentrations of vitamin D metabolites did not differ in normal men and women. There were highly significant seasonal oscillations for 25(OH)D and 24,25(OH)2D3 but not for 1,25(OH)2D. Women with endometriosis had significantly elevated serum 1,25(OH)2D compared to the normal women. Our study indicates that ageing is not associated with a significant depletion of 25(OH)D, 24,25(OH)2D or 1,25(OH)2D in normal men and women up to the age of 75 years. Furthermore, changes in vitamin D metabolism seem not to be an important factor in early postmenopausal bone loss. Our results on patients with endometriosis indicate that these patients may have some calcium-metabolic disturbances.

Does calcium supplementation prevent postmenopausal bone loss? A double-blind, controlled clinical study

During a two-year study, we examined the effect of calcium supplementation on postmenopausal bone loss in 43 women in the early postmenopausal period who were assigned to one of three treatment groups: percutaneous 17 beta-estradiol (combined with progesterone during the second year), oral calcium (2000 mg daily), and placebo. All participants were examined every three months. Bone mineral content in the forearm (measured by single-photon absorptiometry) and in the entire body and spine (measured by dual-photon absorptiometry) remained constant in the estrogen-treated group but decreased significantly in the groups receiving calcium and placebo. In the calcium-treated group, we observed a tendency toward a slowed loss of compact bone (in the proximal forearm and total skeleton) as compared with the placebo group, while the rate of loss of trabecular bone (the distal forearm and spine) was the same as in the placebo group. Our preliminary data suggest that calcium supplementation in the dosage we used is not as effective as estrogen therapy for the prevention of early postmenopausal bone loss. Calcium supplementation may have had a minor effect on the loss of cortical bone, but it had no effect on the trabecular bone.

Does 24R,25(OH)2-vitamin D3 prevent postmenopausal bone loss?

The effect of oral 24R,25(OH)2-vitamin D3 as a prophylactic for postmenopausal bone loss was examined. Fifty-eight healthy, early postmenopausal women entered a double blind therapeutic trial for 2 years. After an initial examination the women were randomized to treatment with 10 micrograms 24R,25(OH)2D3 daily or placebo. Participants were thereafter examined every 3 months (nine examinations in all). In both groups the forearm bone mineral (measured by single photon absorptiometry), the lumbar spine mineral, and the total body mineral (measured by dual photon absorptiometry) fell significantly and at the same magnitude. Furthermore, serum calcium, serum alkaline phosphatase concentration, and fasting urinary hydroxyproline were unchanged, as were the 24-hour urinary calcium excretion and the intestinal radiocalcium absorption. Our findings demonstrate that 24R,25(OH)2D3 treatment has no prophylactic effect on postmenopausal bone loss and does not alter calcium metabolic variables.