Pulsatile secretion pattern of growth hormone in dogs with pituitary-dependent hyperadrenocorticism

Lee, W.M; Meij, B.P; Bhatti, S.F.M; Mol, J.A; Rijnberk, A; Kooistra, H.S

« Previous Next »Domestic Animal Endocrinology
Volume 24, Issue 1 , Pages 59-68, January 2003

Pulsatile secretion pattern of growth hormone in dogs with pituitary-dependent hyperadrenocorticism

W.M Lee
- Department of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine, Utrecht University, P. O. Box 80, 154, NL-3508 TD Utrecht, The Netherlands
- Corresponding author. Tel.: +31-30-2539411; fax: +31-30-2518126.
B.P Meij
- Department of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine, Utrecht University, P. O. Box 80, 154, NL-3508 TD Utrecht, The Netherlands
S.F.M Bhatti
- Department of Small Animal Medicine and Clinical Biology, Ghent University, Salisburylaan 133, B-9820 Merelbeke, Belgium
J.A Mol
- Department of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine, Utrecht University, P. O. Box 80, 154, NL-3508 TD Utrecht, The Netherlands
A Rijnberk
- Department of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine, Utrecht University, P. O. Box 80, 154, NL-3508 TD Utrecht, The Netherlands
H.S Kooistra
- Department of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine, Utrecht University, P. O. Box 80, 154, NL-3508 TD Utrecht, The Netherlands

Received 16 April 2002; accepted 22 July 2002.

Abstract

The amplitude and frequency of growth hormone (GH) secretory pulses are influenced by a variety of hormonal signals, among which glucocorticoids play an important role. The aim of this study was to investigate the pulsatile secretion pattern of GH in dogs in which the endogenous secretion of glucocorticoids is persistently elevated, i.e. in dogs with pituitary-dependent hyperadrenocorticism (PDH). Blood samples for the determination of the pulsatile secretion pattern of GH were collected at 10-min interval between 08:00 and 14:00h in 16 dogs with PDH and in 6 healthy control dogs of comparable age. The pulsatile secretion patterns of GH were analyzed using the Pulsar program.

GH was secreted in a pulsatile fashion in both dogs with PDH and control dogs. There was no statistical difference between the mean (±S.E.M.) basal GH level in dogs with PDH (0.7±0.1μg/l) and the control dogs (0.6±0.1μg/l). The mean area under the curve (AUC) for GH above the zero-level in dogs with PDH (4.6±0.6μg/l per 6h) was significantly lower than that in the control dogs (7.3±1.0μg/l per 6h). Likewise, the mean AUC for GH above the base-level in dogs with PDH (0.6±0.1μg/l per 6h) was significantly lower than that in the control dogs (3.7±1.0μg/l per 6h). The median GH pulse frequency in the dogs with PDH (2 pulses/6h, range 0–7 pulses/6h) was significantly lower (P=0.04) than that (5 pulses/6h, range 3–9 pulses/6h) in the control group.

The results of this study demonstrate that PDH in dogs is associated with less GH secreted in pulses than in control dogs, whereas the basal plasma GH concentrations were similarly low in both groups. It is discussed that the impaired pulsatile GH secretion in dogs with PDH is the result of alterations in function of pituitary somatotrophs and changes in supra-pituitary regulation.

Keywords: Dog, Growth hormone, Glucocorticoids, Hyperadrenocorticism, Pulsatile secretion, Pituitary-dependent hyperadrenocorticism (PDH), Cushing’s syndrome