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Precocious Puberty

Wednesday 4 April 2018 11:02am

Puberty can be one of the most difficult phases in a person’s life, and for some it happens much earlier than expected. Professor Ursula Kaiser, from Harvard Medical School, is an expert on precocious puberty and spoke to CNE researchers about how her research into the area is progressing.

Under normal circumstances reproductive hormones, including gonadotrophin releasing hormone and luteinising hormone, are active during fetal development in order to facilitate sexual differentiation. These hormones are active again after birth, for between 6 months and 2 years, before becoming inactive. In the lead up to puberty these hormones become active once again, fuelling the changes we associate with maturation. “Somehow,” Ursula says, “it’s programmed into us for this system to be reactivated roughly eight or nine years after birth.” This reactivation may be the key to understanding why some children undergo precocious puberty, and begin maturation long before their peers.

Ursula and her team believe that a key factor in female precocious puberty is the gene MKRN3. A genome wide association study of over 182,000 women found that the gene is related to the age of menarche, the age at which women experience their first period. The removal of MKRN3 in chromosomal disorders, such as Prader-Willi syndrome, have also been seen to impact puberty onset. “We saw that when MKRN3 was lost from the chromosome in Prader-Willi syndrome the patient would usually have precocious puberty,” Ursula says, “but if MKRN3 was conserved there was a much more classical expression of Prader-Willi with [late puberty onset].”

It looks like MKRN3, and the protein it produces, act as a kind of brake on the pre-puberty increase in reproductive hormones. “The issue is with that reactivation in the activity of these hormones,” Ursula says, “which is why we see children going through precocious puberty around 6 or 7 rather than around 2 years old, which is what you’d see if these hormones failed to become inactive.” Mutations in the MKRN3 gene, in the case of precocious puberty, render it ineffective and so, without that brakes on to say ‘not yet’, there is a resurgence in reproductive hormones and puberty begins early.

Going through puberty early isn’t going to immediately harm these children, but it does put them at a higher risk for other problems later on. “The earlier you go through puberty the higher your risk of obesity, diabetes, metabolic disorders, breast cancer, and cardiovascular diseases,” Ursula says, “but one of the bigger problems we see are psychosocial behavioural effects, because these kids are going through puberty so much earlier than their peers.” There are treatments to prevent further development once the disorder is identified, but they can’t reverse the initial effects of puberty on these young children. With a genetic marker, like MKRN3, it may be possible to screen children to see whether they’re at risk for the disorder, to give parents the chance to prepare for their child’s future.