title: Growth hormone secretion pattern is an independent regulator of growth hormone actions in humans.
abstract: The importance of gender-specific growth hormone (GH) secretion pattern in the regulation of growth and metabolism has been demonstrated clearly in rodents. We recently showed that GH secretion in humans is also sexually dimorphic. Whether GH secretion pattern regulates the metabolic effects of GH in humans is largely unknown. To address this question, we administered the same daily intravenous dose of GH (0.5 mg. m(-2). day(-1)) for 8 days in different patterns to nine GH-deficient adults. Each subject was studied on four occasions: protocol 1 (no treatment), protocol 2 (80% daily dose at 0100 and 10% daily dose at 0900 and 1700), protocol 3 (8 equal boluses every 3 h), and protocol 4 (continuous GH infusion). The effects of GH pattern on serum IGF-I, IGF-binding protein (IGFBP)-3, osteocalcin, and urine deoxypyridinoline were measured. Hepatic CYP1A2 and CYP3A4 activities were assessed by the caffeine and erythromycin breath tests, respectively. Protocols 3 and 4 were the most effective in increasing serum IGF-I and IGFBP-3, whereas protocols administering pulsatile GH had the greatest effects on markers of bone formation and resorption. All GH treatments decreased CYP1A2 activity, and the effect was greatest for pulsatile GH. Pulsatile GH decreased, whereas continuous GH infusion increased, CYP3A4 activity. These data demonstrate that GH pulse pattern is an independent parameter of GH action in humans. Gender differences in drug metabolism and, potentially, gender differences in growth rate may be explained by sex-specific GH secretion patterns.
authors.affiliation: Divisions of Endocrinology and Metabolism, University of Michigan Medical Center, Ann Arbor, Michigan 48109, USA. cjaffe@umich.edu
authors.forename: Craig A
authors.initials: CA
authors.lastname: Jaffe
authors.forename: D Kim
authors.initials: DK
authors.lastname: Turgeon
authors.forename: Kenneth
authors.initials: K
authors.lastname: Lown
authors.forename: Roberta
authors.initials: R
authors.lastname: Demott-Friberg
authors.forename: Paul B
authors.initials: PB
authors.lastname: Watkins
mesh_terms: D015415:Biomarkers; D001842:Bone and Bones / Q000378:metabolism; D019388:Cytochrome P-450 CYP1A2 / Q000378:metabolism; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D005260:Female; D019382:Human Growth Hormone / Q000008:administration & dosage* / Q000172:deficiency / Q000378:metabolism*; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008297:Male; D020551:Pulse Therapy, Drug; D012727:Sex Characteristics
chemical_list: D015415:Biomarkers; D018972:Insulin-Like Growth Factor Binding Protein 3; D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I; D003577:Cytochrome P-450 Enzyme System; C104464:CYP3A protein, human; D019388:Cytochrome P-450 CYP1A2; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human