ALTERED GROWTH-HORMONE SECRETORY DYNAMICS IN PREPUBERTAL MALES WITH CONSTITUTIONAL DELAY OF GROWTH

We have used the technique of deconvolution analysis to determine if abnormalities in growth hormone (GH) secretion or metabolic clearance underlie the observed alterations in circulating hormone concentrations in a group of seven prepubertal males with constitutional delay of growth (SHORT-DBA). The results were compared with data obtained from 13 healthy, short prepubertal males (SHORT) and 11 healthy prepubertal male subjects of normal stature (NORMAL). Although the mean 12-h overnight GH production rates were invariant among the groups (8.0 +/- 1.0 versus 7.3 +/- 0.7 versus 6.7 +/- 1.2 mug/L, NORMAL versus SHORT versus SHORT-DBA for all comparisons), different secretory mechanisms were operative. The secretory burst half-duration (time interval of the secretory event at half-maximal amplitude) of the SHORT-DBA subjects (26 +/- 1 min) was greater (p = 0.02) than that of the SHORT group (20 +/- 1 min); values for both the SHORT and SHORT-DBA subjects were indistinguishable from that of NORMAL controls (22 +/- 2). Both the mass of GH released per secretory episode and the maximal rate of hormone secretion were less (p less-than-or-equal-to 0.02 and p < 0.01, respectively) for the SHORT-DBA subjects [16 +/- 2 mug/unit of body distribution volume (L(v)) and 0.6 +/- 0.1 mug/L(v)/min, respectively] compared with those of the NORMAL (26 +/- 2 mug/L, and 1.1 +/- 0.1 mug/L(v)/min, respectively) and SHORT (28 +/- 4 mug/L, and 1.3 +/- 0.2 mug/L(v)/min. respectively) groups; values for the latter two groups were indistinguishable. Given the dominant association of GH pulse amplitude with normal childhood growth, the present findings suggest a possible GH secretory mechanism underlying the suboptimal growth in a subset of prepubertal males with constitutional delayed growth.