Background: The female gonadal axis is activated in mini-puberty and thereafter it is quiescent until puberty. We have shown that many girls with no clinical sign of puberty in the age group 1-6 yr. have a rather strong luteinizing hormone (LH) and follicle stimulating hormone (FSH) response to a gonadotropin releasing hormone (GnRH) test. However, stimulated LH and FSH values decreased in the age interval 1-6 yr and no LH/FSH values rose above 0.43. Serum estradiol has until recently not been detectable in pre-pubertal girls after the mini-puberty, but with new highly sensitive techniques estradiol may be measurable in most 1-6 yr. old girls. As both estradiol and inhibin B are produced in the granulosa cells we have examined how they associate in the age interval 1-6 yr.
Objective and hypothesis: The objectives of the study were to investigate the associations between serum (se) estradiol, se inhibin B, GnRH stimulated LH (LH30 ) and sex hormone binding proteins (SHBG) in the age group 1-6 yr.
Methods: Forty eight healthy girls aged 3.5 ± 0.2 yr. (range 0.8 5.9 yr.) were included in the study. All girls underwent a GnRH test. Estradiol concentrations were determined by on-line TurboFlow-liquid chromatographytandem mass spectrometry, inhibin B by two-sided enzyme-linked immunosorbent assay, LH30 and SHBG by sandwich immunometry (Cobas 8000).
Results: Estradiol was measurable in samples from 40 girls. Medians and interquartile ranges were: se estradiol 6.66 (4.47;8.32) pmol /L, se inhibin B 13.00 (8.00;21.50) pg/ml, se LH30 3.43 (2.39;5.19) IU/L, se SHBG 154 (114;177) nmol/L. Se estradiol (r=-0.42, P<0.01), se inhibin B (r=-0.38, P<0.01), se LH30 (r=-0.59, P<001) but not se SHBG (r=0.07, P=0.66) decreased significantly by age. Se estradiol associated positively with se inhibin B (r=0.69, P<0001), while there were no associations between se estradiol and se LH30 and se SHBG, respectively. Neither did se inhibin B associate with se LH30 (r=-0.10, P=0.51).
Conclusion: By ultrasensitive technique circulating estradiol was measurable in most pre-pubertal girls in the age group 1-6 yr. Se estradiol and se inhibin B decreased in the age interval 1-6 yr. We observed a positive association between se estradiol and se inhibin B. This association did not seem to be LH driven.
19 - 21 Sep 2019
European Society for Paediatric Endocrinology