Insulin-like growth factor I: a possible metabolic signal involved in the regulation of female puberty.
In both rats and primates, including humans, serum levels of insulin-like growth factor I (IGF-I) increase during the onset of puberty, suggesting a role for IGF-I in this process. We examined the ability of IGF-I to affect the release of hypothalamic luteinizing hormone releasing hormone (LHRH) in prepubertal female rats. Our results indicate that IGF-I acts on the median eminence, which contains the highest density of type 1 IGF receptors in the brain, to elicit a dose-related increase in LHRH release. In this regard, a minimal effective dose of 10 ng/ml (p less than 0.05) and a maximal effective dose of 100 ng/ml (p less than 0.01) was observed. IGF-II and insulin were one order of magnitude less effective. The results demonstrate that IGF-I has the capability to act directly upon the median eminence to effect release of LHRH, thereby suggesting a role for IGF-I in facilitating peripubertal changes in LHRH release. Thus, IGF-I may represent one of the 'metabolic signals' thought to be involved in the initiation of puberty.
Hiney
J K
JK
Department of Veterinary Anatomy, Texas A&M University, College Station.
Ojeda
S R
SR
Dees
W L
WL
D000818:Animals; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D012741:Sexual Maturation / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology*
D007987:Gonadotropin-Releasing Hormone; D007334:Insulin-Like Growth Factor I