Enhancement of cholinergic tone by pyridostigmine promotes both basal and growth hormone (GH)-releasing hormone-induced GH secretion in children of short stature.

Abstract

Increased cholinergic tone induced by pyridostigmine (PD) increases basal plasma GH levels and potentiates the GH response to GHRH in normal adults. In this study the effects of PD (60 mg, orally) on both basal and GHRH (1 microgram/kg)-induced GH secretion in seven children with familial short stature (FSS), six with GH deficiency (GHD) and 10 with constitutional growth delay (CGD) were studied and compared with results obtained by stimulation with insulin-induced hypoglycemia (IH) and GHRH alone. The mean peak plasma GH levels were variable, but individual values were frequently low in all groups after both IH [FSS, 9.7 +/- 1.3 (+/- SEM) ng/mL; GHD, 1.6 +/- 0.4 ng/mL; CGD, 7.0 +/- 0.8 ng/mL] and GHRH (FSS, 23.8 +/- 6.6 ng/mL; GHD, 11.1 +/- 5.8 ng/mL; CGD, 15.1 +/- 4.5 ng/mL) administration. PD induced GH responses (FSS, 14.5 +/- 1.6 ng/mL; GHD, 3.8 +/- 0.8 ng/mL; CGD, 18.3 +/- 3.2 ng/mL) that in many children in the FSS and CGD groups were higher than those after IH and GHRH treatment. PD clearly increased the GH response to GHRH in all children [FSS, 69.5 +/- 9.4 ng/mL (P less than 0.01 vs. other stimuli); GHD, 18.0 +/- 7.5 ng/mL; CGD, 50.0 +/- 8.5 ng/mL (P less than 0.01 vs. other stimuli)]. We conclude that in children with short stature, as in adults, enhancement of cholinergic tone increases both basal and GHRH-induced GH secretion, and that PD plus GHRH is the best provocative stimulus for evaluating the somatotroph response.