Review of the concept of vitamin D "sufficiency and insufficiency"
There has been a poor consensus in defining normal levels of 25(OH) D. It has been traditionally recognized that 25(OH)D serum levels below 5-7 ng/ml induce osteomalacia, serum levels below 10-12 ng/ml induce secondary hyperparathyroidism and osteoporosis, and serum levels above 18-20 ng/ml are usually considered normal or adequate. Due to the results obtained in several studies, a more functional classification has recently been proposed defining serum 25(OH)D levels > 40 ng/ml or > 100 nmol/l as "desirable", serum levels between 20 and 40 ng/ml or 50 and 100 nmol/l as hypovitaminosis D, levels between 10 and 20 ng/ml or 25 and 50 mmol/l as vitamin D insufficiency and 25(OH)D levels below 10 ng/ml or 25 nmol/l as deficient. These new cut-off levels, suggest that, in the past, we had been using a wrong statistical approach for defining "normal serum 25(OH)D levels". In agreement with this new classification, in a recent study conducted in a random sample of our population, a high prevalence of low levels of 25(OH)D and secondary hyperparathyroidism was found. In our study, only in those people having "excellent" renal function, representing only 15% of the sample (serum creatinine < 1 mg/dl in men and < 0.8 in women, mean age of 68 years) hyperparathyroidism was not diagnosed despite observing 25(OH)D serum levels around 18-30 ng/ml or 45-75 nmol/l). In the remaining people (85% of the sample), who showed the expected serum creatinine increments according to their age, secondary hyperparathyroidism was avoided only if the serum 25(OH)D levels were higher than 30 ng/ml or 75 nmol/l. These remarkable findings demonstrate the importance of maintaining higher 25(OH)D levels--in addition to normal calcitriol levels--in order to avoid stimulation of the parathyroid gland. In 87 patients with a functioning renal transplantation only a 11.5% of they had levels of 25(OH)D higher than 30 ng/ml and it was correlated with PTH. These remarkable findings demonstrate the importance of maintaining higher 25(OH)D levels--in addition to normal calcitriol levels--in order to avoid stimulation of the parathyroid gland in aged people. Thus, the deficiency or even "subtle deficiency" of 25(OH)D, currently neglected in the daily management of patients with chronic renal failure, may play an important role in the maintenance of hormonal and mineral homeostasis.
Available from: Ramon Jesús Zabalza
- "In order to assess the initial vitamin D status in the global DS group, we have not compared our results with a control group, but used deficiency and insufficiency criteria most in keeping with the real situation. Selected cut-off values obtained from population studies, some of which are in our geographical area (Gó mez Alonso et al., 2003b), are mainly based on the reverse relationship between 25 OH vitamin D3 levels and intact parathyroid hormone, the first being an independent hyperparathyroidism predictor (Chapuy et al., 2002; Gó mez Alonso et al., 2003a; Vieth et al., 2003; Lips, 2004). "
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ABSTRACT: To assess the status of vitamin D and the effects of calcium and vitamin D3 supplementation on the bone metabolism in a group of adults with Down's syndrome (DS).
Randomized, parallel, controlled and open clinical trial.
Institution for mentally handicapped: Fundación Uliazpi, Diputación Foral de Guipúzcoa, San Sebastián, Spain.
A total of 23 persons with DS, residents at the Uliazpi Foundation were recruited and all completed the study.
In all, 12 participants were randomly allocated to receive 1 g of calcium and 800 IU of vitamin D once daily for 1 year while 11 were assigned to the control group, receiving no supplementation.
We found no differences between groups regarding serum calcium and phosphorous levels. The remaining parameters showed differences between the two groups consistent with a beneficial effect of the intervention: serum levels of parathyroid hormone, osteocalcin and crosslaps diminished while serum 25 OH vitamin D3 level increased.
The results obtained allow to include people with DS as a risk group with regards to vitamin D deficit, which that can be corrected with vitamin D and calcium supplementation, and giving rise to an improvement of the biochemical markers related to the phospho-calcium metabolism and bone remodelling.
European Journal of Clinical Nutrition 06/2006; 60(5):605-9. DOI:10.1038/sj.ejcn.1602357 · 2.71 Impact Factor
Available from: Shuvayu S Sen
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ABSTRACT: Vitamin D inadequacy has been studied extensively, due to concerns about ageing populations, associations with osteoporosis and other disorders (including non-musculoskeletal), and high prevalence.
To review recent reports on the prevalence of vitamin D inadequacy among post-menopausal women with and without osteoporosis and/or other musculoskeletal diseases.
We reviewed publications in the past 10 years reporting prevalence estimates for vitamin D inadequacy, reported as serum 25(OH)D values below various levels. Thirty published studies in the English language were identified, from January 1994 through April 2004.
In osteoporotic populations, the prevalence of 25(OH) vitamin D concentration <12 ng/ml ranged from 12.5% to 76%, while prevalence rates reached 50% to 70% of patients with a history of fracture(s) using a cut-off of 15 ng/ml. In post-menopausal women, the prevalence of 25(OH) vitamin D concentrations <or=20 ng/ml ranged from 1.6% to 86% for community-living and institutionalized women, respectively. The most common factors associated with inadequate vitamin D levels included limited sun exposure, lack of dietary vitamin D intake, nursing home environment, wintertime, and increasing age (over 70 years).
The prevalence of inadequate vitamin D levels appears to be high in post-menopausal women, especially in those with osteoporosis and history of fracture. Vitamin D supplementation in this group might offer scope for prevention of falls and fracture, especially in elderly and osteoporotic populations.
QJM: monthly journal of the Association of Physicians 10/2005; 98(9):667-76. DOI:10.1093/qjmed/hci096 · 2.50 Impact Factor
Available from: José Portolés
Nefrologia: publicacion oficial de la Sociedad Espanola Nefrologia 02/2006; 26 Suppl 3:103-8. · 1.22 Impact Factor
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