Calcium homeostasis and mineralization in puberty.

Calcium homoeostasis and bone mineralization have been the subject of many studies, but few have dealt with these aspects specifically in puberty. The main observations in our own studies - together with those in other recent reports - are summarized below. According to the aims of the present survey (Chapter 1) the results are grouped as follows: BLOOD MINERAL HOMOEOSTASIS AND ALKALINE PHOSPHATASE. The serum concentrations of calcium, total or ionized, remain remarkably constant throughout puberty, which probably reflects the important functions of the calcium ion. Serum phosphate, however, remain high in childhood, increase slightly with acceleration of growth and pubertal development and the levels then decrease toward adult values. Consequently, the pattern of the product of serum calcium and phosphate, essential for mineralization, follows that of phosphate. Serum magnesium does not change during puberty. The serum concentrations of alkaline phosphatase increase with acceleration in linear growth and pubertal development which has to be taken into consideration, in evaluation of changes in serum AP. Changes in osteoblastic activity, as expressed by AP (and BGP), are closely associated with changes in testosterone secretion with almost simultaneous increases in serum levels of both variables. It is further concluded that longitudinal study designs may add to the understanding of the growth process and rate of changes, whereas cross-sectional data are relevant to establish proper reference ranges. BONE MINERAL CONTENT. The use of photon absorptiometry in determining BMC is a precise, easy, atraumatic and reproducible method. It is shown that forearm BMC has a highly significant correlation to total body bone mineral also in the pubertal period of rapid growth. It should be noted that single measurements of BMC are of little diagnostic value in the presence of wide biological variation. A spurt in mineralization corresponding to that of height in puberty has been known since the development of the BMC technique. It is evident from our data that BMC and indices of body size are only significantly related after the start of the growth spurt. Significant increases of 25% in the BMC have been found in the year prior to PHV progressing with each PH stage. The mean time of maximal increase in forearm BMC occurred some 5 months later than that of testosterone and AP, and changes in these three variables are closely interrelated. The change in the serum concentrations of the two major adrenal androgens did not appear to be related to BMC.(ABSTRACT TRUNCATED AT 400 WORDS)