Unlike normal subjects, in patients with anorexia nervosa (AN) the GH response to GHRH is refractory to the increasing and inhibitory effect of cholinergic agonists and antagonists, respectively. This cholinergic impairment could reflect malnutrition-induced exhaustion of acetylcholine (Ach) precursors. We studied whether treatment with glycerophosphocholine (GLY), an Ach precursor, could disclose the potentiating effect of pyridostigmine (PD) on the GH response to GHRH in AN. In 6 young women with AN (AW) we studied the GH response to iv GHRH (1.0 microg/kg) alone and combined with oral PD (120 mg) before and after 1 month of oral treatment with GLY (400 mg thrice daily). Eight age-matched normal women (NW) were studied as controls. Before GLY, basal GH levels in AW were higher (p < 0.05) than in NW. The GH response to GHRH in AW was higher (p < 0.05) than in NW. PD failed to modify the GHRH-induced GH rise in AW, while it enhanced it in NW (p < 0.05). One month treatment with GLY in AW did not modify the GH response to GHRH either alone or combined with PD. This study shows the existence of a derangement in the cholinergic control of somatotroph function in AN and indicates that treatment with Ach precursors does not exert any effect on this impairment. This could reflect primary alterations of cholinergic neurons, though the effectiveness of more prolonged treatment and/or higher doses of cholinergic precursors needs to be verified.