The effect of calcium supplementation on the circadian rhythm of bone resorption.

摘要: Bone resorption shows a circadian rhythm in human subjects, but the physiological mechanisms underlying this are unknown. We compared of bone collagen degradation 18 premenopausal women before and after oral calcium supplementation (1000 mg for 14 days). Subjects were randomized to receive at either 0800 h or 2300 h. Continuous 48-h urine collections 1 day 4-h obtained 14-day period. measured urinary deoxypyridinoline (Dpd) cross-linked N-telopeptide type I (NTx) as biochemical markers resorption. There was significant effect time on excretion Dpd NTx (analysis variance, P < 0.001) with peak between 0300-0700 nadir 1500-1900 The mean amplitude (peak trough) similar (70.3% 63.3%, respectively). Evening resulted marked suppression nocturnal increase reversed usual level parathyroid hormone. In contrast, morning had no NTx. suppressed overall daily by 20.1% (P = 0.03) 18.1% 0.03). Morning conclude that evening suppresses PTH secretion intake is likely be an important determinant rhythm. Experimental protocols designed investigate mineral density should take timing into account.