Glucose-dependent insulinotropic polypeptide induced growth hormone secretion in acromegaly.
Glucose-dependent insulinotropic polypeptide (GIP), a peptide released from the intestines after meals, is thought to stimulate insulin secretion. GIP receptor cDNA has recently been cloned and its mRNA has been recognized in several organs including the pituitary, but the physiological roles of GIP receptors of the pituitary have yet to be determined. We have demonstrated the possibility that GIP stimulates GH secretions from the pituitary adenoma cells of acromegalics. GIP-stimulated GH responses were studied in four acromegalics. In two acromegalics whose GH showed paradoxical secretion to oral glucose tolerance test (OGTT), GIP infusion (0.6 microg/kg/h) drove GH secretion (13.7 to 68.1, 22.5 to 76.2 ng/ml, respectively). However, in the other two acromegalics whose GH showed no paradoxical response to OGTT, GIP infusion did not induce GH secretion. One of the patients who was studied extensively had a GH that responded to OGTT. This patient's serum GH levels increased after meals while adenomectomy abolished both the paradoxical GH secretions by OGTT and GH responses to the GIP infusion. These data suggested that some somatotroph adenoma cells have an aberrant response to GIP which may go toward explaining paradoxical GH secretions to OGTT in acromegalics.
Umahara
Mitsuhiko
M
Public Nanokaichi Hospital, Department of Internal Medicine, Tomioka-shi, Gunma, Japan.
Okada
Shuichi
S
Ohshima
Kihachi
K
Mori
Masatomo
M
D000172:Acromegaly / Q000378:metabolism*; D000368:Aged; D005260:Female; D005749:Gastric Inhibitory Polypeptide / Q000008:administration & dosage / Q000494:pharmacology*; D005951:Glucose Tolerance Test; D019382:Human Growth Hormone / Q000378:metabolism*; D006801:Humans; D007275:Injections, Intravenous; D008875:Middle Aged; D019518:Postprandial Period
D019382:Human Growth Hormone; D005749:Gastric Inhibitory Polypeptide