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This Article Full Text Full Text (PDF) Supplemental Tables All Versions of this Article: 297/2/E367    most recent 00230.2009v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Veldhuis, J. D. Articles by Bowers, C. Y. PubMed PubMed Citation Articles by Veldhuis, J. D. Articles by Bowers, C. Y.

Relative effects of estrogen, age, and visceral fat on pulsatile growth hormone secretion in healthy women

Departments of ¹Internal Medicine and ²Obstetrics and Gynecology, Endocrine Research Unit, Clinical Translational Research Unit, Mayo Medical and Graduate Schools of Medicine, Mayo Clinic, Rochester, Minnesota; and ³Endocrine Division, Department of Medicine, Tulane University Health Sciences Center, New Orleans, Louisiana

Submitted 6 April 2009 ; accepted in final form 26 May 2009

Growth hormone (GH) secretion is subject to complex regulation. How pre- and postmenopausal age (PRE, POST), estradiol (E₂) availability, and abdominal visceral fat (AVF) jointly affect peptidyl-secretagogue drive of GH secretion is not known. To this end, healthy PRE (n = 20) and POST (n = 22) women underwent a low- vs. high-E₂ clamp before receiving a continuous intravenous infusion of GH-releasing hormone (GHRH) or GH-releasing peptide (GHRP-2). According to analysis of covariance, PRE and POST women achieved age-independent hypo- and euestrogenemia under respective low- and high-E₂ clamps. All four of age (P < 0.001), E₂ status (P = 0.006), secretagogue type (P < 0.001), and an age x peptide interaction (P = 0.014) controlled pulsatile GH secretion. Independently of E₂ status, POST women had lower GH responses to both GHRH (P = 0.028) and GHRP-2 (P < 0.001) than PRE women. Independently of age, GHRP-2 was more stimulatory than GHRH during low E₂ (P = 0.011) and high E₂ (P < 0.001). Stepwise forward-selection multivariate analysis revealed that computerized tomographic estimates of AVF explained 22% of the variability in GHRH action (P = 0.002), whereas age and E₂ together explained 60% of the variability in GHRP-2 drive (P < 0.001). These data establish that age, estrogen status, and AVF are triple covariates of continuous peptide-secretagogue drive of pulsatile GH secretion in women. Each factor must be controlled for to allow valid comparisons of GH-axis activity.

somatotropin; growth hormone-releasing hormone; growth hormone secretion; growth hormone-releasing peptide; human; estrogen