Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P02774 (Gc-globulin)
 196 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We evaluated the effect of estrogens on "free" and total calcitriol levels and on the calcitriol response to a hypocalcemic challenge in 12 postmenopausal women, age 55-74 yr. Endogenous calcitriol production was induced by intravenous Na-EDTA before and after conjugated estrogens, 1.25 mg/d for 30 d. Free calcitriol was determined by centrifugal ultrafiltration and by the molar ratio of calcitriol to vitamin D-binding protein (DBP). Estrogen increased fasting total calcitriol from 38.5 +/- 3.8 to 62.3 +/- 7.0 pg/ml (P less than 0.05). This was accompanied by a rise in free calcitriol from 104.5 +/- 11.4 to 158.7 +/- 16.4 fg/ml (P less than 0.05). Vitamin D-binding protein increased from 348 +/- 16 to 428 +/- 12 micrograms/ml (P less than 0.001), and the ratio of calcitriol/DBP increased from 1.50 +/- 0.14 to 1.94 +/- 0.18 (P less than 0.005), confirming the rise in free calcitriol. Increases in free calcitriol and in calcitriol/DBP ratios were significantly correlated, r = 0.72. Hypocalcemia led to a rapid increase in circulating immunoreactive parathyroid hormone, and to a rise in calcitriol at 24 h. The hypocalcemia-induced rise in total and free calcitriol was similar before and after estrogen, whether expressed as increments or as percent changes. We conclude that estrogen increases circulating levels of biologically active free calcitriol in postmenopausal women, but that a 30-d period of estrogen administration does not apparently improve the renal 1 alpha-hydroxylase response to a PTH challenge.
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PMID:Effects of estrogen on circulating "free" and total 1,25-dihydroxyvitamin D and on the parathyroid-vitamin D axis in postmenopausal women. 249 9

Prior studies showed conflicting results regarding the association between 25-hydroxyvitamin D (25(OH)D) levels and mineral metabolism in end-stage renal disease. In order to determine whether the bioavailable vitamin D (that fraction not bound to vitamin D-binding protein) associates more strongly with measures of mineral metabolism than total levels, we identified 94 patients with previously measured 25(OH)D and 1,25-dihydroxyvitamin D (1,25(OH)(2)D) from a cohort of incident hemodialysis patients. Vitamin D-binding protein was measured from stored serum samples. Bioavailable 25(OH)D and 1,25(OH)(2)D were determined using previously validated formulae. Associations with demographic factors and measures of mineral metabolism were examined. When compared with whites, black patients had lower levels of total, but not bioavailable, 25(OH)D. Bioavailable, but not total, 25(OH)D and 1,25(OH)(2)D were each significantly correlated with serum calcium. In univariate and multivariate regression analysis, only bioavailable 25(OH)D was significantly associated with parathyroid hormone levels. Hence, bioavailable vitamin D levels are better correlated with measures of mineral metabolism than total levels in patients on hemodialysis.
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PMID:Bioavailable vitamin D is more tightly linked to mineral metabolism than total vitamin D in incident hemodialysis patients. 2269 77