Parathyroid hormone hypercalciuria

The overall effect in most animals is to stimulate intestinal absorption of calcium with a concomitant increase in semm calcium and a reduction in parathyroid hormone (PTH). Modest hypercalcemia allows the glomerular filtration rate to remain stable and hypercalciuria to occur because of increased filtered load of calcium and reduction of tubular resorption of calcium with reduced PTH. However, with further increases in semm calcium, the glomerular filtration rate decreases, resulting in an even more rapid increase in semm calcium and the subsequent fall in urinary calcium. 

In rats, infusion of the insulin secretagogues arginine and glucose induced a calciuria proportional to serum insulin levels. Suppression of insulin secretion by mannoheptulose or streptozotocin prevented the calciuria. Parathyroidectomy did not affect arginine-induced hypercalciuria in the rat, so insulin is not inhibiting parathyroid hormone secretion or activity. 

We have tested the hypothesis that insulin inhibits the stimulatory effect of parathyroid hormone (PTH) on calcium reabsorption in the distal nephron. PTH is known to enhance calcium transport in renal cells, probably by stimulation of adenylate cyclase and subsequent increases in 3 5 cyclic AMP productoin. Since insulin had been observed to inhibit PTH-stimulated increases in kidney cyclic AMP levels in vitro (24) we investigated whether insulin-mediated hypercalciuria was dependent on the presence of PTH in vivo. 

Cholecalciferol Regulate gene transcription via the vitamin D receptor Stimulate intestinal calcium absorption, bone resorption, renal calcium and phosphate reabsorption decrease parathyroid hormone (PTH) promote innate immunity inhibit adaptive immunity Osteoporosis, osteomalacia, renal failure, malabsorption Hypercalcemia, hypercalciuria the vitamin D preparations have much longer half-life than the metabolites and analogs... 

Mild asymptomatic hypercalcemia is common during treatment with parathyroid hormone (15). The hypercalcemia is persistent, and requires dosage reduction in 3% of patients using 20 micrograms/day and in 11% using 40 micrograms/day (16). Transient mild hypercalciuria and increased serum phosphate are common but do not usually limit therapy. 

In the kidneys, parathyroid hormone increases 1 -hydroxylation of calcidiol and reduces 24-hydroxylation. This is not the result of de novo enzyme synthesis, but an effect on the activity of the preformed enzymes, mediated by cAMP-dependent protein kinases. In turn, calcitriol has a direct role in the control of parathyroid hormone, acting to repress expression of the gene. In chronic renal failure, there is reduced synthesis of calcitriol, leading to the development of secondary hyperparathyroidism that results in excess mobilization of bone mineral, hypercalcemia, hypercalciuria, hyperphosphaturia, and the development of calcium phosphate renal stones. 

Adverse effects of oral calcium and vitamin D supplementation include hypercalcemia and hypercalciuria, especially in the hy-poparathyroid patient, in whom the renal calcium-sparing effect of parathyroid hormone is absent. Hypercalciuria may increase the risk of calcium stone formation and nephrolithiasis in susceptible patients. One maneuver to help prevent calcium stones is to maintain the calcinm at a low normal concentration. Monitoring 24-hour urine collections for total calcium concentrations (goal <300 mg/24 h) may also minimize the occurrence of hypercalciuria. The addition of thiazide dinretics for patients at risk for stone formation may result in a reduc-tionof both urinary calcium excretion and vitamin D requirements." ... 

Randomised trials A randomised, controlled trial of 6 months of parathyroid hormone treatment in combination with either concurrent or sequential ibandronate over 2 years [67 ] found that both treatment regimens were efficacious in increasing bone mineral density in postmenopausal women (N = 44). Seven women met the criteria for hypercalcaemia, with only one requiring reduction in treatment. Three women met the criteria for hypercalciuria. The most commonly reported adverse events were nausea (32%) and injection-site reactions (32%). 

Hyperparathyroidism results from oversecretion of PTH. This condition leads to excessive bone turnover and demineralization and must be treated by removal of the parathyroid gland. The disorder is classified into primary, secondary, and tertiary hyperparathyroidism. Sporadic primary hyperparathyroidism is the third most common endocrine disorder, after diabetes and hyperthyroidism. It is most common in females older than 55 years of age and the leading cause is a single adenoma, which secretes the hormone constitu-tively, without regulation. Symptoms can include osteopenia and bone fractures, renal stones resulting from hypercalciuria, peptic ulcer disease, and pancreatitis. In milder cases, patients are asymptomatic or suffer only muscle weakness, fatigue, and/or depression. 

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