The effect of pirenzepine on the growth hormone response to growth hormone-releasing hormone in obese children

We studied the effect of pirenzepine, a cholinergic antagonist, on the GH response to GH-releasing hormone (GHRH) in 6 obese children (4 males and 2 females) aged 5.3-12.8 years with excess body weight ranging from 42 to 125% for their stature. A GHRH test was also performed in 8 short normal children (5 males and 3 females, age 6.8-11 years) studied as controls. In the obese patients two GHRH (GHRH 1-29, 1 μg/Kg iv) tests were performed 3-7 days apart in random order. Sixty min before the GHRH bolus the patients received placebo or pirenzepine (50 mg po). Mean peak and area under the curve (AUC) responses to GHRH were significantly lower in the obese subjects than in the control group. Administration of pirenzepine caused a significant reduction of both peak and AUC responses to GHRH in all obese children. Our findings show that administration of a cholinergic antagonist suppresses the already blunted GH response to GHRH in obese children. These and other previous findings indicate the presence of an intact somatostatinergic system in obesity.