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Changes in dimeric inhibin A and B during normal early puberty in boys and girls
Author(s) -
Crofton P. M.,
Illingworth P. J.,
Groome N. P.,
Stirling H. F.,
Swanston I.,
Gow S.,
Wu F. C. W.,
McNeilly A.,
Kelnar C. J. H.
Publication year - 1997
Publication title -
clinical endocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.055
H-Index - 147
eISSN - 1365-2265
pISSN - 0300-0664
DOI - 10.1046/j.1365-2265.1997.d01-1744.x
Subject(s) - prepuberty , medicine , endocrinology , testosterone (patch) , menarche , luteinizing hormone , menstrual cycle , hormone , biology
OBJECTIVE Although recently developed specific and sensitive assays of bioactive dimeric inhibin A and B have given new insights into the pituitary‐gonadal axis in adult men and during the adult female menstrual cycle, there have been no reports on circulating inhibin A and B during normal human puberty. The aim of this study was to assess the relationship of dimeric inhibin A and B to pubertal stage, FSH and testosterone or oestradiol in late prepuberty and in early puberty.STUDY DESIGN AND SUBJECTS Serial samples were collected during a prospective longitudinal trial of GH treatment in short normal children. Seven boys were studied from late prepuberty to genital stage 3, and six pre‐menarche girls from late prepuberty to breast stage 4.MEASUREMENTS Dimeric inhibin A (girls only) and inhibin B (boys and girls) were measured by highly specific and sensitive two‐site ELISAs, FSH by IRMA, testosterone and oestradiol by RIA.RESULTS In boys, inhibin B increased progressively from pubertal stages 1 to 3 (ANOVA P <0.0001) and correlated strongly with mean testicular volume ( r =0.72, P =0.0005). Prepubertal boys showed a positive correlation between inhibin B and FSH ( r =0.65, P =0.056), whereas pubertal boys gave a strong negative correlation ( r =0.75, P =0.012). In both prepubertal and pubertal boys positive correlations were observed between inhibin B ( y ) and testosterone ( x ) ( r =0.81, P =0.008 and r =0.62, P =0.054 respectively), but the slope of the regression line between the two was much steeper before than after the onset of clinical puberty. In girls, both inhibin A and B increased through pubertal stages 1–4 (ANOVA P =0.01 and P =0.047 respectively). Both showed strong positive correlations with oestradiol ( r =0.80 and 0.79, P =0.001) and with FSH ( r =0.83, P =0.0004 and r =0.80, P =0.001). Inhibin A and B were also strongly correlated with each other ( r =0.92, P =0.0001).CONCLUSIONS In boys, testicular production of inhibin B increases as puberty progresses. Our results show for the first time that the initiation of puberty is accompanied by a dramatic switch from a positive to a negative relation between inhibin B and FSH as inhibin B begins to exert the expected negative feedback on FSH. The results in girls suggest that, prior to menarche, the ovarian follicles produce inhibin A and B in strict proportion, and in progressively greater amounts as puberty proceeds. Measurement of dimeric inhibin A and B may provide a sensitive new tool for determining gonadal maturity in late prepuberty and early puberty.