The pituitary-adrenal response to CRF-41 is unaltered by intravenous somatostatin in normal subjects

We have previously reported that the hypothalamo-pituitary-adrenal response to insulin-induced hypoglycaemia is normal while the cortisol release to pituitary stimulation by corticotrophin releasing factor (CRF-41) is reduced in obesity. Impaired growth hormone (GH) secretion is also found in obesity which may result from altered central levels of somatostatin (SMS). We have investigated, by giving a simultaneous infusion of SMS to six volunteer normal weight men during a CRF test, whether it is possible for SMS to modify pituitary-adrenal function. Each subject received intravenous CRF-41 (0.5 micrograms/kg) on two occasions during an infusion of isotonic saline or SMS (4 micrograms/min) in a randomized double-blind study. Plasma GH, cortisol, ACTH and SMS were measured. Three subjects demonstrated GH peaks during saline infusion but no peaks were seen in any subject during SMS infusion. No significant difference was found between peak cortisol responses during saline or SMS infusion (SMS cortisol 443 +/- 61 nmol/l, saline cortisol 485 +/- 52 nmol/l); neither was there any difference in the ACTH responses. We conclude that SMS does not alter the pituitary response to CRF in normal weight men and is thus less likely to be responsible for the altered pituitary-adrenal function seen in obesity. Further studies of alternative mechanisms are required to explain the cause of this abnormality.