title: Impact of short-term estrogen administration on growth hormone secretion and action: distinct route-dependent effects on connective and bone tissue metabolism.
abstract: We recently reported that estrogen exerts distinct effects on the GH/IGF-1 axis that are dependent on the route of delivery, probably reflecting a first-pass effect on hepatic IGF-1 production. Oral administration reduces IGF-1 and increases GH levels; transdermal administration elevates IGF-1 without changing GH concentrations. Since mesenchymal tissue is a target for GH and IGF-1 action, we studied changes in the GH/IGF-1 axis following oral (ethinyl estradiol, 20 micrograms/day) versus transdermal (Estraderm 100 TTS, Ciba Geigy, 100 micrograms 17 beta-estradiol per day) estrogen delivery and compared corresponding effects on connective and bone tissue metabolism. Mean 24 h GH levels, IGF-1, markers of fibroblast (procollagen III) and osteoblast (procollagen I, osteocalcin) function, and indices of bone turnover (fasting urinary hydroxyproline and calcium to creatinine ratios, UOHPr/Cr and UCa/Cr) were measured before and after 2 months of either oral or transdermal therapy in two groups of postmenopausal women. Transdermal estrogen administration significantly (p less than 0.05) increased IGF-1, procollagen III, procollagen I, osteocalcin, and UOHPr/Cr. In contrast, oral estrogen administration had a suppressive effect; the levels of IGF-1 (p = 0.001), procollagen III (p = 0.018), procollagen I (p = 0.002), osteocalcin (p = 0.015), and UOHPr/Cr (p = 0.004) were significantly different from those measured during transdermal administration. Both treatments significantly reduced UCa/Cr (p less than 0.015). IGF-1 changes during estrogen therapy were significantly related (p less than 0.05) to changes in procollagen III, procollagen I, osteocalcin, and UOHPr/Cr. Transdermally delivered estrogen stimulates IGF-1 production, increases osteoblastic function, and stimulates bone and nonbone collagen synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Garvan Institute of Medical Research, St. Vincent's Hospital, Sydney, New South Wales, Australia.
authors.forename: K K
authors.initials: KK
authors.lastname: Ho
authors.forename: A J
authors.initials: AJ
authors.lastname: Weissberger
mesh_terms: D000279:Administration, Cutaneous; D000284:Administration, Oral; D001842:Bone and Bones / Q000378:metabolism*; D003094:Collagen / Q000097:blood; D003238:Connective Tissue / Q000378:metabolism*; D004958:Estradiol / Q000008:administration & dosage / Q000494:pharmacology*; D004997:Ethinyl Estradiol / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D005640:Follicle Stimulating Hormone / Q000097:blood; D013006:Growth Hormone / Q000097:blood / Q000378:metabolism*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000097:blood; D008875:Middle Aged; D010006:Osteoblasts / Q000378:metabolism
chemical_list: D004997:Ethinyl Estradiol; D004958:Estradiol; D007334:Insulin-Like Growth Factor I; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D013006:Growth Hormone; D003094:Collagen