The role of endogenous growth hormone-releasing hormone in acromegaly.
BACKGROUND
Some indirect evidence suggests hypothalamic control of GH secretion in acromegaly.


OBJECTIVE
The objective of the study is to examine whether GH secretion in acromegaly is dependent on endogenous GHRH.


METHODS
We studied eight patients with untreated acromegaly due to a GH-producing pituitary tumor. All patients received an iv infusion of normal saline for 24 h and GHRH-antagonist (GHRH-ant) at 50 microg/kg x h for 7 d. GH was measured every 10 min for 24 h during the normal saline infusion and on the last day of the GHRH-ant infusion. A group of nine different patients with untreated acromegaly served as the control group and underwent blood sampling for GH every 10 min for two 24-h periods to assess the day-to-day variability of GH secretion.


METHODS
The study was set in a university referral center.


METHODS
Twenty-four-hour mean GH was the main outcome measured.


RESULTS
In six of eight subjects treated with GHRH-ant, 24-h mean GH decreased by 5.8-30.0% during iv GHRH-ant and, in three subjects, the change in the 24-h mean GH was greater than the upper limit of the 95% confidence interval of the spontaneous day-to-day variability of the mean GH in patients with acromegaly. Based on the binomial distribution, the probability of this magnitude of change to occur in three of eight subjects by chance alone is 0.0008.


CONCLUSIONS
In some patients with acromegaly due to a pituitary adenoma, GH secretion is under partial control by endogenous GHRH.
Department of Internal Medicine, Division of Metabolism, Endocrinology and Diabetes, University of Michigan, Ann Arbor, Michigan 48109, USA. e-dimaraki@northwestern.edu
Eleni V
EV
Dimaraki
William F
WF
Chandler
Morton B
MB
Brown
Craig A
CA
Jaffe
Soo Y
SY
Kim
Ronald
R
Taussig
Vasantha
V
Padmanabhan
Ariel L
AL
Barkan
D000172:Acromegaly / Q000378:metabolism*; D000236:Adenoma / Q000378:metabolism*; D000328:Adult; D005260:Female; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000235:genetics; D005951:Glucose Tolerance Test; D013007:Growth Hormone-Releasing Hormone / Q000502:physiology*; D019382:Human Growth Hormone / Q000097:blood / Q000378:metabolism*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000032:analysis; D008297:Male; D008875:Middle Aged; D009154:Mutation; D010911:Pituitary Neoplasms / Q000378:metabolism*
D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I; D013007:Growth Hormone-Releasing Hormone; D019205:GTP-Binding Protein alpha Subunits, Gs