Plasma and urinary GH following a standardized exercise protocol to assessGH production in short children

Plasma and urinary GH responses following acute physical exercise were eval uated in 19 short-statured children (12 males, 7 females, median age: 11.4 yr, age range: 6.1-14.5 yr, Tanner stage I-III, height less than or equal t o3(rd) centile for age; 7 with familial short stature, FSS; 8 with constitu tional growth delay, CGD; 4 with Chi deficiency, GHD) and 7 normally growin g, age- and sex-matched control children (4 males, 3 females, median age 11 .0 yr, range: 7.2-13.1 yr, Tanner stage I-III). All patients and controls u nderwent a standardized exercise protocol (consisting of jogging up and dow n a corridor for 15 min, strongly encouraged to produce the maximum possibl e effort, corresponding to 70-80% of the maximal heart rate) after an overn ight fasting. Samples for plasma Chi determinations were drawn at 0 time (b aseline), at 20 min (5 min after the end of exercise) and at 35 min (after 20 min of rest); urine samples were collected before (0 time) and at 40, 80 and 120 min after exercise. The distance covered by children with GHD duri ng the test was significantly lower (p<0.05) than in the other groups of pa tients and controls. No differences in the pattern of plasma GH responses a fter physical exercise were found between children with FSS, CGD and health y controls, the maximum percent increase (vs baseline) being evident at 20 min (median, FSS: +1125%; CGD: +1271%; controls: +571%). Children with GHD showed a smaller percent increase (+94%) of plasma GH, significantly lower (p<0.01) than those recorded in the other groups. A significant percent inc rease (p<0.01) of baseline urinary Chi following exercise was found in chil dren with FSS (median: +34%), CGD (+18%) and controls (+44%). Children with FSS and CGD showed a gradual increase of urinary Chi, reaching the maximum at 80 min, while healthy controls had a more evident and precocious increa se (maximum at 40 min). Urinary median GH levels did not change following p hysical exercise in children with GHD (-5%, not significant). A significant correlation was found between the maximal percent increase (vs baseline) o f plasma and urinary GH following physical exercise (r-0.7, p<0.001). In co nclusion, our results show that: 1) plasma and urinary GH responses las wel l as the distance covered and the number of steps, i.e. the physical perfor mance) to a standardized exercise protocol are similar in children with FSS , CGD and in normal-statured controls, being unable to differentiate among the "normal variants" of growth; 2) children with GHD, unable to accomplish the same performance of the other three groups, show significantly reduced plasma and urinary GH responses following physical exercise. Although the determination of GH responses to pharmacological stimuli remains the defini tive tool for the diagnosis of GHD, these preliminary results seem to sugge st a potential role of urinary land plasma) GH response to a standardized e xercise protocol as a safe, acceptable first screening test for GH sufficie ncy also in children, as previously reported in adults. (J. Endocrinol. Inv est. 24: 515-521, 2001) (C) 2001, Editrice Kurtis.