[Daily secretion of parathyroid hormone in adult subjects]

Data reported in the literature on the existence of a circadian rhythm in PTH secretion are contradictory. In order to assess whether haematic PTH levels vary over a 24 hour period, the plasma levels of the hormone were evaluated at 6 different times during the day (12, 19, 24, 2, 4, 6 hours) in a group of 10 healthy adults (5 males, 5 females), aged from 24.8 to 48.7 years. PTH values were determined by the double antibody radioimmunological method using commercially available kits (PTH-K Sorin-Saluggia), whose antiserum reacts with C terminal fraction of the hormone. No statistically significant differences were observed, either between the sexes or among the samples collected during the 24 hour period. The results therefore seem to preclude the existence of a circadian rhythm in PTH secretion. However, further studies and more data - based on RIA methods, whose antiserum reacts with the N terminal of the hormone - would be necessary to preclude the existence of rapid circadian variations in PTH over the 24 hour period.