Sex differences in FSH-regulatory peptides in pubertal age boys and girls and effects of sex steroid treatment.
BACKGROUND
FSH concentrations are higher in girls than in boys before puberty. We hypothesized that steroid-mediated changes in FSH-regulatory proteins underlie the sex differences in FSH secretion and pubertal timing.


METHODS
FSH-regulatory proteins, LH, FSH and sex steroids were measured in five boys, 10 girls, and five girls with Turner syndrome before and during sex steroid treatment (girls, 0.05 mg/day estradiol; boys, 5 mg/day testosterone) for up to 4 weeks. Blood was obtained every 15 min from 20.00 to 08.00 h before and during sex steroid treatment.


RESULTS
The mean FSH concentration was higher in girls than in boys (P = 0.0044). Activin-A concentrations were greater (P < 0.0001) and inhibin-B concentrations lower (P < 0.0001) in girls compared with boys. Steroid treatment (i) suppressed LH/FSH concentrations in all subjects; (ii) increased the mean activin-A concentration in all but the Turner girls (P = 0.001); and (iii) decreased inhibin-B concentrations in boys (P = 0.005) but not in girls. Total follistatin and follistatin 288 concentrations did not differ by sex.


CONCLUSIONS
Sex steroids regulate circulating activin-A and inhibin-B concentrations in children. The lower inhibin-B and higher activin-A concentrations may explain the higher FSH and earlier onset of puberty in girls.
Foster
Carol M
CM
Department of Pediatrics/Endocrinology and the Reproductive Sciences Program, University of Michigan, Ann Arbor, MI 48109, USA. cmfoster@umich.edu
Olton
Pamela R
PR
Racine
Michael S
MS
Phillips
David J
DJ
Padmanabhan
Vasantha
V
D028341:Activins / Q000097:blood*; D000293:Adolescent; D000375:Aging / Q000097:blood*; D002648:Child; D004958:Estradiol / Q000627:therapeutic use; D005260:Female; D005640:Follicle Stimulating Hormone / Q000378:metabolism*; D012739:Gonadal Steroid Hormones / Q000627:therapeutic use*; D006801:Humans; D028322:Inhibin-beta Subunits / Q000097:blood*; D007265:Inhibins / Q000097:blood*; D008297:Male; D011627:Puberty / Q000097:blood*; D012727:Sex Characteristics; D013739:Testosterone / Q000627:therapeutic use; D014424:Turner Syndrome / Q000188:drug therapy / Q000378:metabolism*
D012739:Gonadal Steroid Hormones; C422405:activin A; C422364:inhibin B; D028341:Activins; D013739:Testosterone; D004958:Estradiol; D007265:Inhibins; D005640:Follicle Stimulating Hormone; D028322:Inhibin-beta Subunits