Short-term changes in urinary growth hormone excretion and lower leg length in healthy children

To investigate any association between changes in lower leg length (LLL) and urinary growth hormone (uGH) excretion, 4 prepubertal children supplied daily 12-hour overnight urine samples and had daily knemometry performed for 4 weeks. The mean daily and weekly LLL velocity (LLLV) of the group was (0.08 mm/day (95% CI 0.01-0.18) and 0.52 mm/week (range 0.38-0.78), respectively. The mean uGH excretion was 8.9 ng/l (CI 3.7-13.3), and the mean intrasubject coefficient of variation of uGH was 55% (range 32-93). The tallest subject who also had the highest LLLV excreted the least amount of uGH (mean 3.7 ng/l, CI 2.9-4.5). No temporal relationship was evident between daily uGH excretion and LLLV. There was no evidence of any association between amount of uGH excreted and LLLV. There remains some doubt on the usefulness of uGH measurement as the sole predictor of normal GH production.