medwireNews: A study of infant girls has characterised the hormonal changes of minipuberty and uncovered how the ovaries, uterus and reproductive hormones interrelate during this period.
The findings indicate “that negative feedback in the female hypothalamic-pituitary-gonadal axis is established during minipuberty, with ovarian activity promoting uterine and glandular breast tissue growth”, the researchers write in the Journal of Clinical Endocrinology & Metabolism.
Margit Bistrup Fischer (Copenhagen University Hospital – Rigshospitalet, Denmark) and co-workers used information from The Copenhagen Analgesic Study (COPANA) of prenatal exposure to paracetamol on 302 infant girls aged an average of 3.4 months, which they say is around the “expected peak of minipuberty.”
This included transabdominal ultrasound ovary measurements for 203 girls and blood samples for 269 girls.
Overall, 152 girls had ovarian follicles of 2–4 mm and 165 girls had follicles of 5 mm or larger at the time of their ultrasound scan, 81.0% of the 302 participants had palpable glandular breast tissue and 5.6% had vaginal bleeding related to minipuberty.
The researchers found that total follicle count was significantly and positively associated with ovarian volume, as well as with levels of anti-Müllerian hormone and inhibin B. Similarly, the number of follicles of 5 mm or larger in size was significantly and positively correlated with levels of anti-Müllerian hormone, inhibin B, oestrone, oestradiol, progesterone and testosterone. There were also significant and negative correlations between both follicle count and follicles of at least 5 mm in size and levels of follicle-stimulating hormone.
In addition, oestradiol concentration was significantly associated with the size of oestrogen-responsive tissues in the infants – namely, uterine volume and endometrial thickness – while both oestradiol and oestrone levels significantly correlated with glandular mammae tissue diameter.
Fischer and co-authors note that infants with intrauterine fluid visible on ultrasound had significantly lower levels of oestradiol than those without.
Girls with intrauterine bleeding during minipuberty had a significantly larger uterine volume than those who did not (1527.2 vs 1184.8 mm3). Uterine volume was also significantly and positively associated with body weight and length, whereas there was no such relationship between ovarian volume and these measurements.
The researchers say their study allowed the creation of age-related normative values for ovarian volume and follicle counts, uterine volume, length and anteroposterior width, the transverse diameter of the uterine fundus, endometrial thickness and glandular mammae tissue diameter.
However, they note that as all infant girls in the study were born full term, “the results may therefore not apply to preterm girls, for whom minipuberty tends to be prolonged and highly active compared to full-term girls.”
All girls were White so the results may also not apply to infants of other ethnicities, the researchers add.
By Lynda Williams
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