The effects of
cholinergic muscarinic receptor antagonist
pirenzepine on the GHRH-induced GH release were studied in 10 adolescent females with
anorexia nervosa at different stages of the disease, in 5 adolescent females with
eating disorders and in 5 normal adolescents. The patients were characterized according to psychological (DSM III-R), endocrinological (
GnRH test), nutritional (Somatomedin-C, T3), and clinical (% IBW, duration of the amenorrhoea) criteria. On two separate occasions, each subject received an i.v. bolus injection of
GHRH 1-40 (1 microgram/kg) alone or preceded by
pirenzepine (0.6 mg/kg i.v. 5 min before
GHRH 1-40).
GHRH 1-40 injection induced a significantly (P less than 0.05) higher GH increase in the patients with
anorexia nervosa at the acute stage as compared with the controls.
Pirenzepine did not abolish opportunely the exaggerated GH response to
GHRH 1-40 in
anorectic patients at the acute stage unlike the control, who showed the blockade of GHRH-induced GH release by the
cholinergic muscarinic antagonist (P less than 0.05). The
anorectic adolescents at the non acute stage and the adolescents with
eating disorders showed varying reductions of GH response; however,
pirenzepine produced a blunted suppression of GHRH-induced GH increase as compared to the controls, which was not statistically significant.
Somatomedin-C values were significantly (P less than 0.05) lower in
anorectic patients at the acute stage as compared with controls. The abnormal activity of
cholinergic system in
anorectic patients, as our data show, could induce the GH hypersecretion through an inhibitory influence on the somatostatinergic function. The reduced
somatomedin-C levels, a specific
malnutrition index in
anorectic patients, produce a modified feed-back on the hypothalamic site (
somatostatin) and/or directly on the pituitary, following the GH hypersecretion.