Growth-Hormone Secretory Patterns Aid To Diagnosis Of Growth Problems

Since GH responses to provocative (PGH) stimuli are often not reflective of physiological GH secretion, PGH was compared with integrated physiological GH secretion (ICGH) in 133 children and adolescents ages 4-18, with abnormal growth (<5th or >95th % for height and/or abnormal growth velocity). ICGH was determined by continuous ambulatory blood withdrawal pump (collected in one hr aliquots) over 12 h (1800-0600) or 24 h (1800-1800) in 87, or by 12 h intermittent q 20 min sampling (1800-0600) in 46 patients. The following morning all children had either arginine-insulin (AI) induced hypoglycemia (118) or oral clonidine (C) (15) tests. Serum somatomedin C, T/E2, bone age and T4 were also correlated with growth velocity and GH responses. In 33, 24 h ICGH correlated highly with, but was not more informative than 12 h ICGH (1800-0600) performed in all patients. Discordant GH levels (PGH vs ICGH, × and peaks) were present in 47 of 120 (40-50% of children with constitutional delay (CD) of growth), depending on the criteria for normality used. Low ICGH (<2 ng/ml) was seen in 42, and borderline ICGH (2-3 ng/ml) in 21. Low (<7 ng/ml) or borderline (7-10 mg/ml) GH responses to AI or C were seen in 48 and 19 children respectively. ICGH was useful in excluding a Dx of GH deficiency (GHD) in 14 patients with low PGH, while the Dx GHD was further substantiated in 26 patients. ICGH proved most valuable in patients with CD-delayed adolescence and/or emotional stress where “transient” GHD and discordant GH values are often obtained on pharmacologic testing.