Nancy D. Adams

The calciuria of increased fixed acid production in humans: Evidence against a role for parathyroid hormone and 1,25(OH)2-vitamin D

SummaryWe measured mineral and acid balances, serum iPTH, urinary cAMP/creatinine, and plasma concentrations of 25OHD and 1,25(OH)2D in 7 healthy adults during control conditions and during increased fixed acid production achieved either by the administration of NH4Cl (N=3) or by increased dietary protein intake (N=4). When acid production was increased, the subjects were in positive acid balance and negative Ca balance because of increased urinary Ca excretion. Serum iPTH fell slightly but urinary cAMP and the plasma levels of vitamin D metabolites did not change. We conclude that the accelerated skeletal and urinary losses of Ca that occur when fixed acid production is increased are not contributed to nor compensated for by the parathyroid-vitamin D endocrine systems.

Renal Osteodystrophy—Pathogenesis and Treatment

Histologic bone changes of osteitis fibrosa and osteomalacia are commonly present in patients with end-stage renal disease. Although many patients are not symptomatic from these bone changes, some patients are severely disabled. Altered metabolism of vitamin D, calcium, phosphorus, and parathyroid hormone occurs in renal failure and contributes to the development of uremic bone disease. This article reviews the current theories of pathogenesis and treatment of renal osteodystrophy. In addition, the clinical presentation, pathogenesis, and treatment of the various aluminum-associated osteomalacic syndromes in uremia are discussed.

Calcium-Oxalate-Crystal-Induced Bone Disease

A 13-year-old boy with primary hyperoxaluria and a successful renal allograft developed symptomatic bone disease, hypercalcemia, and hypercalciuria. Transiliac bone biopsy revealed calcium oxalate crystals in the marrow within mononuclear phagocytes and multinucleated giant cells. Deep resorption bays were seen adjacent to these crystal-cell aggregates. Serum 1,25-(OH)2-vitamin D (calcitriol) and iPTH concentrations were low or normal. We suggest that hypercalcemia results from macrophage-mediated bone resorption initiated by Ca oxalate crystal deposition.

Absence of Anion Gap Metabolic Acidosis in Severe Methanol Poisoning: A Case Report and Review of the Literature

Methanol poisoning in humans is characterized by a latent period with subsequent development of anion gap metabolic acidosis and blindness. We describe a patient with potentially lethal methanol ingestion as evidenced by an admission serum methanol level of 403 mg/dL and sustained serum methanol levels greater than 50 mg/dL for more than 18 hours after ingestion, despite hemodialysis therapy. That anion gap metabolic acidosis or visual impairment did not develop in this patient was attributed to documented prior ethanol ingestion (admission serum ethanol level of 158 mg/dL) and continued ethanol administration during hospitalization (sustained serum ethanol levels greater than 100 mg/dL). This case demonstrates the ability of ethanol to inhibit the metabolism of methanol to formic acid in humans. This inhibition was achieved without induction of lactic acidosis. Thus this case documents the efficacy of ethanol therapy in patients with methanol poisoning.

Review: Renal Osteodystrophy—Pathogenesis Treatment

ABSTRACT Histologic bone changes of osteitis fibrosa and osteomalacia are commonly present in patients with end-stage renal disease. Although many patients are not symptomatic from these bone changes, some patients are severely disabled. Altered metabolism of vitamin D, calcium, phosphorus, and parathyroid hormone occurs in renal failure and contributes to the development of uremic bone disease. This article reviews the current theories of pathogenesis and treatment of renal osteodystrophy. In addition, the clinical presentation, pathogenesis, and treatment of the various aluminum-associated osteomalacic syndromes in uremia are discussed.

Effects of weight loss on serum 1,25-(OH)2-vitamin D concentrations in adults: A preliminary report

SummaryDuring a review of 42 metabolic studies in healthy women and men we observed that serum 1,25-(OH)2-D concentrations were directly correlated to the observed daily changes in body weight (r=0.68;P<0.001) and to caloric intake/kg/day (r=0.39;P=0.01). These relationships could not be accounted for by related and physiologically expected changes in serum Ca or iPTH concentrations. However, serum 1,25-(OH)2-D concentrations were observed to be inversely correlated to serum PO4 levels (r=−0.44;P=0.004). In addition, serum PO4 levels were inversely correlated to the daily changes in body weight (r=−0.40;P=0.009). Since dietary sodium intake averaged 142 mmol/day, it is unlikely that the observed changes in weight were the result of changes in salt and water balance. Thus it seems reasonable to speculate that serum 1,25-(OH)2-D concentrations may vary directly with energy balance, as reflected by changes in body weight. This effect may be mediated by alterations in PO4 metabolism. The accurate assessment of serum 1,25-(OH)2-D levels thus appears to require several measurements over time periods during which body weight is stable.

Effect of high calcium and phosphorus intake on mineral retention in very low birth weight infants chronically treated with furosemide.

The treatment of premature infants with the diuretic furosemide appears to be a contributory factor in the development of metabolic bone disease presumably because of furosemide-induced hypercalciuria. In this study, we measured calcium and phosphorus balance in furosemide-treated very low birth weight infants (VLBW) infants with bronchopulmonary dysplasia (BPD) who were fed a specialized premature formula containing increased amounts of calcium and phosphorus. Furosemide-treated infants received 166 + 37 mg/kg/day and retained 80 + 34 mg/kg/day of calcium, and 87 + 19 mg/kg/day and retained 52 + 14 mg/kg/day of phosphorus. The amounts retained were ~65% of the calcium and 72% of the phosphorus requirements for in utero mineral accretion. Compared to a group of similarly fed VLBW infants without BPD and not treated with the diuretic, the furosemide-treated infants excreted a larger percent of the calcium intake in the urine but had similar total urinary calcium and phosphorus losses (mg/kg/day) and serum calcium, phosphorus, alkaline phosphatase, and parathyroid hormone (PTH) levels. From the latter two findings, we suggest that the extra mineral content of the formula may have promoted bone mineralization and prevented the occurrence of secondary hyperparathyroidism.

Attracting more residents into nephrology.

Understanding what attracts trainees to a specialty, in this case nephrology, is elusive. Some factors relate to the individual, their personality and needs; some factors are related to the field, including characteristics of daily work, patient problems, and an individual’s experience with

The chief medical residency: a description and recommendations.

Individuals occupying the position of chief medical resident have the opportunity to influence significantly the quality and tenor of medical education and medical practice. To assess the status of the position, the authors surveyed chief medical residents completing their tenure in 1980. These residents distributed their time among administrative (41 percent), teaching (35 percent), patient care (21 percent), and research (3 percent) activities. They reported that their experience was quite positive. However, overall satisfaction was significantly negatively correlated with percentage of time spent performing administrative tasks. The percentage of time chief medical residents allocate to administration has increased during the past decade, while time spent teaching and delivering patient care has decreased. Based upon this survey, recommendations for improved utilization of the time and talents of these individuals are presented.

Physiological and Pharmacological Aspects of 24,25-Dihydroxycholecalciferol in Man

The present study describes the response to small oral doses (1--10 microgram/day) of 24,25-DHCC in man. Contrary to expectation, 24,25-DHCC was as potent as 1,25-DHCC in increasing intestinal absorption of calcium both in normal persons and in patients with a variety of disorders of calcium metabolism. Despite this increase in intestinal absorption, plasma and urine calcium did not increase after 24,25-DHCC as they did after 1,25-DHCC. Metabolic balance studies showed calcium balances to increase by 1.6 to 11.5 mmoles/day in 5 of the 6 patients studied. 24,25-DHCC increased intestinal absorption of calcium equally well in anephric patients, suggesting that conversion of 24,25-DHCC to 1,24,25-trihydroxycholecalciferol by the kidney cannot be the sole mechanism by which 24,25-DHCC expresses biological activity, even though in vitamin D deficient rats nephrectomy does abolish the ability of large doses of 24,25-DHCC to increase calcium absorption. It is concluded that 24,25-DHCC may be a calcium-regulating hormone in man. In view of the effects demonstrated here and its relatively high concentration in plasma and slow turnover rate, 24,25-DHCC has the properties that might be ideal for a long-acting stimulator of bone mineralisation. Further work is needed to explain why 24,25-DHCC has effects in man which are not readily seen in other species.