medwireNews: Researchers report a “biphasic and prolonged” minipuberty in girls, and provide reference ranges for reproductive hormones during the first year of life.
“The need for continuous, age-specific reference ranges of the reproductive hormones during the entire first year of life, and particularly during minipuberty, is apparent when diagnosing and managing patients with suspected hypogonadism such as Differences of Sex Development”, observe Marie Ljubicic (University of Copenhagen, Denmark) and study co-authors.
They say: “The unique reference ranges presented here can be directly implemented in other centers if applied with caution”, adding that adjustments may be necessary according to local methods for measuring hormone levels.
The findings are based on data from 98 baby girls who underwent multiple examinations, including blood sampling, throughout the first year of life as part of the COPENHAGEN Minipuberty Study in 2016–2018; 89 girls completed all six examinations. This gave a total of 266 blood samples taken between 5 days and 14.2 months of age, with a median of three samples per baby.
“Interestingly, we observed a biphasic and prolonged female minipuberty”, write the researchers in The Journal of Clinical Endocrinology & Metabolism.
The first peak occurred at around days 15–27 and involved all measured hormones, namely luteinising hormone (LH), follicle-stimulating hormone (FSH), sex hormone-binding globulin (SHBG), oestrone (E1), oestradiol (E2), anti-Müllerian hormone (AMH) and inhibin B.
The second peak occurred at around days 107–125 for the ovarian hormones – inhibin B, AMH, E1, E2 and SHBG – whereas the second peak for the gonadotrophins – LH and FSH – was later, at about days 164–165.
Also, the two peaks were of similar size for inhibin B, AMH and E2, whereas for LH, FSH and E1 the second peak was smaller than the first. Despite these differences, all hormones had the same nadir, between days 58 and 92.
“Our study clearly challenges the general impression of minipuberty being a single and short-lived activation of the HPG [hypothalamic-pituitary gonadal] axis in infancy, which has repercussions for the clinicians aiming to utilize the window of diagnostic opportunity that minipuberty presents”, write the researchers.
“The timing of the two peaks observed in our study suggest that sampling at three months of age may not be the optimal timing”, they add.
All hormones were detectable in almost all samples taken up to 1 year of age, after which LH and E1 became undetectable.
The team says this “high degree of detectability of the ovarian hormones” during the first year of life “indicates that the period of HPG axis activation appears to be longer than previously believed and compared to what has been observed in male infants.”
By Eleanor McDermid
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