Calcitonin, estradiol, and hydroxyproline as parameters in the early diagnosis of involutional osteoporosis. The importance of the "second calcitonin phenomenon".

Bone metabolism was studied in a group of 92 subjects. A greater age-related decrease in calcitonin and estradiol concentrations exists in women than in men, though this difference was not significant; it was significant, however, when the values of the three different groups of women were compared. We present what we have called the second calcitonin phenomenon, that is, a highly significant difference in women between a second basal calcitonin level and the primary admission value. In the calcium infusion test, men considered to be osteoporotic showed a deceleration in the rapid loss of reserve calcitonin deposits.