Francis P. Muldowney

Prevention of hypovitaminosis D in the elderly

SummaryConflicting opinions are held on the efficacy and safety of low-dose oral vitamin D supplementation. In this study, the value of short-term and long-term low-dose vitamin D supplementation (20 μg D3 daily) is demonstrated in elderly subjects. Short-term therapy readily restored serum 25-hydroxy-vitamin D (25OHD) values to normal, and ameliorated biochemical abnormalities of calcium, phosphate, and alkaline phosphatase, consistent with healing of mild osteomalacia. Prolonged therapy (16 months) maintained serum 25OHD levels within the young adult range, and was not associated with hypercalcemia. Withdrawal of therapy was associated with a steady decline in serum 25OHD levels. Low-dose vitamin D supplementation is recommended for elderly subjects to prevent the development of hypovitaminosis D osteopathy.

Ionised calcium levels in ‘Normocalcaemic’ Hyperparathyroidism

SummaryFive subjects presenting with renal stone, hypercalciuria and normal total serum calcium showed persistent elevation of ionised plasma calcium and marginal elevation of plasma parathyroid hormone concentration. Neck exploration revealed a parathyroid adenoma in each, and parathyroidectomy has been followed by reduction in both plasma ionised calcium and urine calcium. Ionised calcium measurement is an important aid in the differential diagnosis of idiopathic hypercalciuria from ‘normo-calcaemic’ hyperparathyroidism.

Determination of ionised calcium by ion selective electrode is not independent of albumin concentration

The relationship of ionised calcium measurement to changes in serum total protein and albumin were studied both in vivo and in vitro. During venostasis serum ionised calcium was determined in 10 control subjects using an Orion SS20 analyser. A slight but significant increase in ionised calcium occurred only after prolonged venostasis (15 min), when gross changes in total protein and albumin were seen. The effect of albumin concentration on serum ionised calcium was studied in vitro by the dialysis technique of Payne. The increase in ionised calcium in 40 sera was 0.0198 mmol/l per 10 g albumin change. We conclude that albumin-related variation in serum ionised calcium determination required such gross changes that correction is rarely necessary in clinical practice. When gross albumin alteration occurs, the appropriate correction for the analyser used should be determined and applied.

Osteomalacia in ureterosigmoidostomy

Summary(1)A case of severe osteomalacia with chronic metabolic acidosis following ureterosigmoidostomy is described.(2)Treatment with alkali reversed the acidosis and induced positive phosphate balance. Maintenance therapy with alkali alone has been continued for twenty-four months without recurrence of symptoms.(3)The role of acidosis in the production of osteomalacia is discussed and it is postulated that acidosis exerts its effect through phosphate depletion.

Serum ionised calcium determination by ion specific electrode, and its value in clinical metabolic disorders

SummaryAmethod is described for determination of serum ionised calcium, using an ion specific electrode. Values recorded in 24 normal subjects, and in various disease states are presented and the clinical value of this measurement discussed.

A case of osteomalacia and renal tubular acidosis associated with occult idiopathic steatorrhoea; the effect of vitamin d on renal tubular hydrion transport

Summary1.A clinical case of osteomalacia secondary to idiopathic steatorrhoea was found to exhibit the biochemical features of renal tubular acidosis.2.Treatment with vitamin D resulted in reversal of systemic acidosis with restoration to normal of renal tubular acidifying power.3.It is suggested that vitamin D is necessary for renal tubular (and perhaps gastro-intestinal) transport of hydrogen and phosphate ions. Evidence from the literature is quoted in favour of the further concept that transport of phosphate, hydrogen ion, glucose and amino-acids may be vitamin D dependent.

Differentiation of hypercalcaemia due to malignancy from primary hyperparathyroidism: The value of parathyroid hormone and plasma bicarbonate measurements

SummaryParathyroid hormone levels in primary hyperparathyroid patients and patients with malignant disease and hypercalcaemia are reported. The value of PTH measurement in conjunction with serum calcium and bicarbonate values in differential diagnosis is discussed. Theories for the production of hypercalcaemia in malignant disease are reviewed.

CAUSES OF ELEVATED BLOOD UREA IN 100 HOSPITAL CASES

SummaryIn this prospective study we examined 100 consecutive in-patients found to have a blood urea concentration greater than 13.3 mmol/l (80 mg/dl) or a serum creatinine concentration greater than 176 μmol/l (2 mg/dl).Pre-renal causes were responsible in 32 of these patients and there was a 40% mortality rate in this subgroup of patients after one month follow up.In 14 cases inappropriate administration of diuretics was a major cause of blood urea elevation.

The long-term effect of parathyroidectomy on renal function.

SummaryRenal function was seen to deteriorate as total serum calcium rose in 40 patients with primary hyperparathyroidism. There is no significant difference between creatinine clearance values measured pre- and post-parathyroidectomy even after an interval of 8 years. This indicates that lowering of serum calcium by parathyroidectomy stabilises renal function, but creatinine clearance does not return to normal values once renal damage has occurred.

Primary hyperparathyroidism: a review of 35 cases.

SummaryA review is presented of 35 cases of primary hyperparathyroidism, studied before and after parathyroidectomy. Presenting clinical features varied widely but were mostly related to renal stone disease. The critical value of serum ionised calcium and parathyroid hormone measurements are emphasized. Metabolic acidosis due to renal bicarbonate wastage was present in 68% and improved significantly following operation.