Acylated ghrelin secretion is acutely suppressed by oral glucose load or insulin-induced hypoglycemia independently of basal growth hormone secretion in humans.
BACKGROUND
Ghrelin has been reported to be the natural ligand of growth hormone (GH) secretagogue receptor, and it is known that exogenous ghrelin administration strongly stimulates GH release in humans. However, the effects of endogenous ghrelin on GH secretion and changes in ghrelin levels during dynamic changes in GH levels are not well understood.


METHODS
Therefore, we measured circulating acylated ghrelin concentrations during oral glucose tolerance tests (OGTTs) in patients with active acromegaly (AA, n = 9) and in age/sex/BMI-matched group A controls (n = 12), and during insulin tolerance testing (ITT) in patients with GH deficiency (GHD, n = 10) and in group B controls (n = 10). Plasma acylated ghrelin, serum GH, insulin and glucose levels were measured during each test.


RESULTS
Fasting plasma ghrelin levels correlated negatively with serum insulin levels in both group A and B controls (r = -0.665; p < 0.05) but not in patients with AA or GHD. During OGTTs, circulating ghrelin levels decreased significantly with a nadir at 30 min in both patients with AA (p < 0.05) and group A controls (p < 0.01). Also, ITTs were followed by a significant decrease in circulating ghrelin levels with a nadir at 30 min in patients with GHD (p < 0.05) and in group B controls (p < 0.05).


CONCLUSIONS
The results of the study show that at baseline acylated ghrelin levels do not differ with respect to the GH status (GH excess or GH deficiency) and, furthermore, the suppression of acylated ghrelin levels during OGTT or ITT is independent of the GH response to the tests.
Kim
Sang Wan
SW
Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
Kim
Kyung Won
KW
Shin
Chan Soo
CS
Park
Do Joon
DJ
Park
Kyong Soo
KS
Cho
Bo Youn
BY
Lee
Hong Kyu
HK
Kim
Seong Yeon
SY
D000172:Acromegaly / Q000097:blood; D000328:Adult; D001786:Blood Glucose / Q000502:physiology*; D016022:Case-Control Studies; D004393:Dwarfism, Pituitary / Q000097:blood; D005260:Female; D054439:Ghrelin; D005951:Glucose Tolerance Test; D019382:Human Growth Hormone / Q000378:metabolism*; D006801:Humans; D007003:Hypoglycemia / Q000097:blood* / Q000139:chemically induced; D007328:Insulin / Q000097:blood / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged; D036361:Peptide Hormones / Q000097:blood / Q000378:metabolism*
D001786:Blood Glucose; D054439:Ghrelin; D007328:Insulin; D036361:Peptide Hormones; D019382:Human Growth Hormone