Insulin-like growth factor I as an intraovarian regulator: basic and clinical implications.
Although much remains to be learned with respect to the possible relevance of IGF-I to ovarian physiology, it may be possible at this time to tentatively formulate possible functions of IGF-I in this connection: 1. Amplification of gonadotropin hormonal action--a key requirement given the exponential nature of follicular development. 2. Integration of follicular development--an essential facet concerned with the coordination of granulosa-theca cooperation. 3. Selection of dominant follicle(s)--a speculative proposition assuming timely and selective activation of the IGF-I system in "chosen" follicles. Aside from its possible role(s) in the course of established follicular cycles, IGF-I (and/or IGF-II) may also participate in the very formation of the follicular apparatus during the late fetal/early neonatal period. Although the ovary is gonadotropin-independent at that time, we previously showed that IGF-I may well interact with VIPergic input now implicated in the morphodifferentiation of the follicular apparatus. Similarly, IGF-I may be concerned with the promotion of juvenile and early pubertal follicular gonadotropin (FSH) levels; ovarian IGF-I may have a bearing on the puberty-promoting effect of growth hormone. Indeed, an association appears to exist between isolated growth hormone deficiency and delayed puberty in both rodents and human subjects, a process reversed by systemic growth hormone replacement therapy. Given that ovarian IGF-I and its receptor may be growth hormone-dependent, it is tempting to speculate that the ability of growth hormone to accelerate pubertal maturation may be due, at least in part, to the promotion of ovarian IGF-I production and reception with the consequent local potentiation of gonadotropin action.
Adashi
E Y
EY
Department of Obstetrics and Gynecology, University of Maryland School of Medicine, Baltimore 21201.
Resnick
C E
CE
Hernandez
E R
ER
Hurwitz
A
A
Roberts
C T
CT
Leroith
D
D
Rosenfeld
R
R
D000818:Animals; D002352:Carrier Proteins / Q000096:biosynthesis; D005260:Female; D006107:Granulosa Cells / Q000502:physiology; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I / Q000378:metabolism / Q000502:physiology*; D010053:Ovary / Q000378:metabolism / Q000502:physiology*; D011956:Receptors, Cell Surface / Q000502:physiology; D017451:Receptors, Somatomedin
D002352:Carrier Proteins; D018969:Insulin-Like Growth Factor Binding Proteins; D011956:Receptors, Cell Surface; D017451:Receptors, Somatomedin; D007334:Insulin-Like Growth Factor I