No abstract

Daily urinary calcium excretion in renal stone-forming subjects is shown to vary directly with moderate changes in dietary sodium intake. The changes produced are sufficient to alter the basic diagnostic classification from 'hypercalciuric' to 'normocalciuric' because dietary sodium is reduced from 200 to 80 mM/day. Similar changes were observed in fasting morning 'spot' urine samples, resulting in alteration of diagnostic subclassification between so-called 'absorptive' and 'renal' categories, in the absence of demonstrable change in parathyroid function. Diagnostic and therapeutic studies in stone-forming subjects require control of both dietary calcium and dietary sodium if misinterpretations are to be avoided. Habitual high sodium intake may be an etiological factor in the generation of excessive excretion of calcium, sodium, and phosphate--the hypercalciuria syndrome.

Background-Hepatic osteodystrophy occurs in the majority of patients with advanced chronic liver disease with the abnormalities in bone metabolism accelerating following orthotopic liver transplantation (OLT). Aims-To examine changes in bone mineral density (BMD) following OLT and to investigate factors that lead to bone loss. Methods-Twelve patients had BMD (at both the lumbar spine (LS) and femoral neck (FN)) and biochemical markers measured preoperatively and for 24 months following OLT. Results-BMD was low in 75% of patients prior to OLT and decreased significantly from baseline at the LS at three months and the FN at six months. BMD began to increase thereafter at both sites, approaching baseline values at the LS by 12 months. Bone formation markers, osteocalcin and procollagen type I carboxy propeptide, decreased immediately post-OLT, with a concomitant increase seen in the resorption markers pyridinoline and deoxypyridinoline. This resulted in a negative uncoupling index early post-OLT, that rebounded to positive values after six months. There was a significant correlation between the change in the uncoupling index between six and three months which preceded the increase in BMD at 12 months. The decrease in BMD recorded early post-OLT correlated with vitamin D levels at three months. Conclusions-Results suggest that increased resorption and inadequate formation are the major contributors to additional bone loss following OLT. Noninvasive biochemical markers precede later changes in BMD in this patient group following OLT and may have a role in investigating and planning intervention strategies to prevent bone loss in future studies. (Gut 1999;44:430-434)

No abstract

The vitamin D status of 181 elderly Irish community-dwelling and institutionalized subjects was studied during Winter-Spring. The mean serum 25-hydroxyvitamin D level was 10 nmol/L (95% range less than 5.0-59 nmol/L); values were below 25 nmol/L in 79 percent of subjects. A significant seasonal variation of serum 25-hydroxyvitamin D levels was noted in elderly community-dwelling subjects. The previously documented age-related increase in serum alkaline phosphatase activity was significantly less in vitamin D replete subjects than in vitamin D deplete subjects in this study (P less than 0.005). The higher serum alkaline phosphatase values found in the vitamin D deplete subjects may represent mild secondary hyperparathyroidism or osteomalacia. The relationship of vitamin D status to both dietary intake and effective sunlight (latitude) is examined.

The relative effects of renal insufficiency and vitamin D deficiency on parathyroid gland function were assessed in 29 free-living elderly subjects by using a sensitive assay for intact parathyroid hormone (PTH). Serum calcium, phosphate, alkaline phosphatase, creatinine, 25-hydroxyvitamin D [25(OH)D], and PTH were measured after an overnight fast during wintertime, after oral vitamin D therapy (20 micrograms cholecalciferol/d for 4 wk), and at the end of the subsequent summer. Hypovitaminosis D [serum 25(OH)D < 25 nmol/L] was evident in 86% of the subjects during wintertime and 52% had elevated PTH concentrations. Multiple-regression analysis identified serum creatinine as the strongest predictor variable for serum PTH (multiple r = 0.73, P < 0.001). Mean (+/- SD) serum PTH declined from 6.3 +/- 2.8 to 5.0 +/- 2.0 pmol/L (P < 0.001) by the end of the summer season, coincident with an increase in serum 25(OH)D). Secondary hyperparathyroidism is common in elderly people, and in Ireland is the result of both renal insufficiency and hypovitaminosis D.

Hepatic osteodystrophy occurs in up to 50% of patients with chronic liver disease (CLD). The aim of this study was to determine the relative contribution of increased resorption and decreased formation to hepatic osteodystrophy by measuring biochemical markers. Twenty-seven patients with advanced CLD (14 female, 13 male) were enrolled. Bone mineral density (BMD), measured at the lumbar spine, and femoral neck, were measured by dual energy X-ray absorptiometry (DXA); bone turnover was assessed using biochemical markers of bone formation and resorption. Based on WHO criteria, osteoporosis and osteopenia were present in 41% and 18% of patients, respectively. All three markers of bone resorption (free deoxypyridinoline, pyridinoline, and hydroxyproline) were increased significantly in patients with CLD. There was a less marked change in the markers of bone formation (osteocalcin, procollagen type 1 peptide, and bone alkaline phosphatase), resulting in a negative uncoupling index in 23/27 (85%) of the patients. Only two (7%) patients had biochemical changes consistent with osteomalacia. The results suggest that increased bone resorption is the predominant cause of hepatic osteodystrophy and therapeutic strategies should be designed to suppress bone resorption, especially in preparation for liver transplantation. Bone biomarkers may be useful alternatives to bone biopsy in evaluating hepatic osteodystrophy.

No abstract