Hypercalciuria due to combined growth hormone and calcitriol therapy in uremia: effects of growth hormone on mineral homeostasis in 75% nephrectomized weanling rats.

The administration of growth hormone (GH) in conjunction with calcitriol in uremia may increase urinary calcium and decrease renal phosphate excretion, which could have an adverse effect on the kidney in chronic renal insufficiency. The effect of 40 d of ovine GH, calcitriol, and the combination of GH and calcitriol on mineral excretion was studied in rapidly growing uremic rats. Uremia was produced by 75% nephrectomy, and the animals were fed a diet containing 8% protein with equal quantities of calcium (0.6%) and phosphate (0.6%). The uremic rats treated with ovine GH were significantly longer and heavier than the uremic control rats and the uremic rats treated with calcitriol alone. However, the combination of calcitriol and GH abolished the beneficial effect of GH on growth and increased urinary calcium excretion 4-fold over uremic controls whether expressed as calcium excretion per 100 g body weight, urine calcium to creatinine ratio, or as fractional calcium excretion. Calcitriol therapy alone also significantly increased calcium excretion, but not to the extent that the combination therapy did. This increased urinary calcium excretion in the GH plus calcitriol group was not associated with an increase in calcium and sodium intake, plasma ionized calcium, or urinary sodium excretion. The calcium content of the femurs from all uremic rat groups was significantly lower than that of the sham control rats; however, there was also no further decrease in bone calcium content in the GH plus calcitriol group compared with uremic controls. This indicated that bone was not the source of this excess urinary calcium.(ABSTRACT TRUNCATED AT 250 WORDS)