Regulation of basal, pulsatile, and entropic (patterned) modes of GH secretion in a putatively low-somatostatin milieu in women

Johannes D. Veldhuis, Susan A. Hudson, Joy N. Bailey, Dana Erickson

Research output: Contribution to journalArticle

Abstract

Somatostatin (SS) released by hypothalamic neurons inhibits GH exocytosis noncompetitively. Therefore, we postulated that attenuation of GH feedback-induced SS outflow would help to unmask covariates of endogenous secretagogue drive. To this end, 42 healthy pre- and postmenopausal women were randomly assigned to receive leuprolide plus estradiol (E2) or leuprolide plus placebo. A putatively low-SS milieu was imposed by L-arginine infusion. Deconvolution and regularity analyses were applied to 6-h GH concentration-time profiles. By two-way ANOVA, age negatively (P < 0.001) and E2 positively (P = 0.001) determined pulsatile GH secretion in the presumptively SS-deficient milieu (P < 0.001). Comparable effects were exerted on the mass of GH secreted per burst per unit distribution volume (age P = 0.001, E2 P < 0.001, overall P < 0.001). E2 alone predicted basal (nonpulsatile) GH secretion (P = 0.004). Stepwise forward-selection multivariate regression demonstrated that age (P = 0.0017) and E2 (P = 0.0002) together explained 46% of intersubject variability in pulsatile GH secretion (P < 0.001) and fully replaced the negative univariate effect of abdominal visceral fat (r2 = 0.32, P < 0.001). Moreover, age and E2 (but not AVF) interacted to supervise GH regularity (P = 0.007). We conclude that age and E2 availability individually and together constitute primary predictors of basal, pulsatile, and patterned GH secretion in an inferentially feedback-silenced context in healthy women. Therefore, both factors must be considered in framing hypotheses of endogenous GH drive.

Original languageEnglish (US)
Pages (from-to)E483-E489
JournalAmerican Journal of Physiology - Endocrinology and Metabolism
Volume297
Issue number2
DOIs
StatePublished - Aug 1 2009

Keywords

  • Female
  • Growth hormone
  • Insulin-like growth factor I
  • Pituitary
  • Somatotropin

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Physiology
  • Physiology (medical)

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