DrugLib.com — Drug Information Portal

Rx drug information, pharmaceutical research, clinical trials, news, and more

Estimation of the size and shape of GH secretory bursts in healthy women using a physiological estradiol clamp and variable-waveform deconvolution model.

Author(s): Veldhuis JD, Keenan DM, Bowers CY

Affiliation(s): Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA. veldhuis.johannes@mayo.edu

Publication date & source: 2007-09, Am J Physiol Regul Integr Comp Physiol., 293(3):R1013-21. Epub 2007 May 30.

Publication type: Randomized Controlled Trial; Research Support, N.I.H., Extramural

Because estrogen production and age are strong covariates, distinguishing their individual impact on hypothalamo-pituitary regulation of growth hormone (GH) output is difficult. In addition, at fixed elimination kinetics, systemic GH concentration patterns are controlled by three major signal types [GH-releasing hormone (GHRH), GH-releasing peptide (GHRP, ghrelin), and somatostatin (SS)] and by four dynamic mechanisms [the number, mass (size), and shape (waveform) of secretory bursts and basal (time invariant) GH secretion]. The present study introduces an investigative strategy comprising 1) imposition of an experimental estradiol clamp in pre- (PRE) and postmenopausal (POST) women; 2) stimulation of fasting GH secretion by each of GHRH, GHRP-2 (a ghrelin analog), and l-arginine (to putatively limit SSergic restraint); and 3) implementation of a flexible-waveform deconvolution model to estimate basal GH secretion simultaneously with the size and shape of secretory bursts, conditional on pulse number. The combined approach unveiled the following salient percent POST/PRE contrasts: 1) only 27% as much GH secreted in bursts during fasting (P < 0.001); 2) markedly attenuated burstlike GH secretion in response to bolus GHRP-2 (29%), bolus GHRH (30%), l-arginine (37%), constant GHRP-2 (38%), and constant GHRH (42%) (age contrasts, 0.0016 </= P </= 0.027); and 3) a 160% prolongation and 32% abbreviation of the time required to achieve maximal GH secretion after injection of l-arginine and bolus GHRP-2, respectively (both, P < 0.001). Accordingly, age selectively determines both the size (amount) and shape (waveform) of GH secretory bursts in healthy women independently of the short-term estrogen milieu.

Page last updated: 2007-10-18

-- advertisement -- The American Red Cross
Home | About Us | Contact Us | Site usage policy | Privacy policy

All Rights reserved - Copyright DrugLib.com, 2006-2017