Changes in plasma inorganic phosphorus and alkaline phosphatase activity during the adolescent growth spurt

Abstract

Longitudinal data on changes in the concentrations of plasma inorganic phosphorus and plasma alkaline phosphatase activity in 23 girls and 44 boys during the adolescent growth spurt are reported together with the height velocities, ages and sexual maturity ratings. The average age at the peak of the growth spurt was 12.5 yr in the girls ans 14.1 yr in the boys with mean annual height gains of 7.0 and 9.7 cm/yr, respectively. In both sexes, plasma alkaline phosphatase activity rose and fell with the growth velocity during the growth spurt. Plasma inorganic phosphorus rose to reach a peak in the 4 mo. before the peak of the growth spurt in height; this rise was statistically significant in the boys but not in the girls. Values subsequently fell rapidly towards the normal adult concentrations. Plasma Ca, total protein and albumin concentrations were also followed during this time, but were not at any point significantly different from normal adult values. These findings provide a guide for the interpretation of plasma biochemistry in adolescent patients.