N. Potau et al., Sexual dimorphism in the maturation of the pituitary-gonadal axis, assessed by GnRH agonist challenge, EUR J ENDOC, 141(1), 1999, pp. 27-34
Objective: To assess whether the maturational changes of the pituitary-gona
dal axis in a healthy population show gender-specific changes and to establ
ish normative data for the different Tanner stages.
Design: Prospective, cross-sectional study.
Methods: The GnRH agonist leuprolide acetate (500 mu g) was administered s.
c, to 60 boys and 81 girls (age range, 5-17 years), Serum steroids and gona
dotropins were determined at 0 and 24 h and at 0, 3 and 24 h after GnRH ago
nist challenge respectively, whereas IGF-I, IGF-binding protein-1 (IGFEP-1)
, IGFBP-3 and sex hormone-binding globulin were measured at baseline.
Results: Baseline and peak LH responses to the agonist in late puberty and
basal and peak FSH levels at all Tanner stages, were higher in girls than i
n boys. Girls showed higher IGF-I levels than boys throughout puberty, shar
per decreases in IGFBP-1 and earlier and greater increases in 17-hydroxypre
gnenolone, dehydroepiandrosterone (DHEA) and DHEA-sulfate. Testosterone res
ponses to the agonist increased during puberty in males, and showed no chan
ges in females. Conversely estradiol responses rose throughout puberty in f
emales and remained unchanged until late puberty in males.
Conclusion: Leuprolide acetate stimulates gonadotropin and gonadal steroid
secretion during puberty in both sexes and increases FSK levels in prepuber
tal girls, Pubertal maturation of gonadotrope function is gender specific,
as it appears to involve increases in both the releasable and reserve pools
of LH in males, and of LH and FSH in females, The earlier increase in Delt
a(5)-steroids in girls may suggest a sharper rise in ovarian cytochrome P45
0c17 activity along the Delta(5)-steroid pathway, while the failure of estr
adiol to increase in response to leuprolide acetate in early pubertal males
suggests a late maturation of aromatase activity.