[Circadian rhythm of parathyrin and calcitonin concentrations in the serum]

The circadian variations of serum intact parathyrin, C-terminal parathyrin (65-84), mid-region parathyrin (44-68) fragments, calcitonin, total calcium, ionized calcium, albumin and phosphate were measured in five healthy subjects. Intact parathyrin, parathyrin (44-68) and calcitonin show a synchronous diurnal fluctuation with a nocturnal increase to a maximum between 24.00 and 2.00 hours. Whereas phosphate has a marked circadian rhythmicity with a zenith between 1.00 and 8.00 hours, total calcium and albumin show a tendency to decrease between 20.00 and 6.00 hours. Ionized calcium concentration remains constant over the whole day.