Scientists have discovered a biological trigger for early puberty

New research from Branhouse's lab reveals how early childhood adversity causes early puberty and anxiety later in life, opening the way for potential interventions.

The age at puberty has been declining for decades.

In the United States, the average age of onset of puberty in girls ranges from 8.8 to 10.3 years. Early onset of puberty, which is associated with many health risks, may be caused by chronic stress in children.

A new study by Northeastern University researchers, published in the journal of Hormones and Behavior, finds for the first time that early childhood stress affects a part of the brain—specifically, a protein. In the cell membrane - responsible for preventing premature onset of puberty.

A receptor in the brain can suppress the release of hormones or “slow down” early puberty. The receptor stops functioning normally under chronic stress, triggering a cascade of signals that leads to early onset of puberty, say researchers from Northeastern University.

Children who experience early puberty are at risk of developing cancers of the reproductive organs and metabolic syndromes such as diabetes, cardiovascular disease, emotional and social problems in adulthood, according to research.

The researchers hope their findings will lead to medical interventions in the future.

"Early puberty is important because it appears to be associated with psychopathologies later in life, such as anxiety disorders," says Heather Branhouse, a professor of psychology at Northeastern University. "Physiological medical conditions may also be associated with early puberty."

The biological mechanism for how early childhood stress leads to early puberty remained largely unknown, notes Branhouse.

New research from Branhouse's lab at Northeastern University has identified a receptor—the part of a brain cell that receives messages from another cell—in the hypothalamus, an area of the brain that controls many body functions through hormones.

From previous research, scientists knew that precocious puberty in girls is associated with early adversity and that early puberty predicts anxiety in adolescence and adulthood.

They set out to confirm these findings and identify the biological trigger for early puberty in the brain.

Lauren Granata, a Northeastern University graduate with a doctorate in psychology, was a co-author of the study and conducted the study in animal models. She initially found the idea that stress causes puberty counterintuitive.

“It is now well known that stress suppresses reproduction,” says Granata. "I thought there were a lot of opportunities to learn something new."

The scientists first confirmed the hypothesis that early childhood adversity actually causes early puberty in rats. Working with an animal model, Granata said, allowed them to isolate one specific factor—a disrupted relationship with the mother—besides other factors such as nutrition.

Of course, Granata adds, what happens in humans doesn't always correlate directly with the animal model, but it is good evidence that maternal dysfunction early in life may be one of the factors regulating early puberty.

“The way you can really traumatize a child or a developing rodent is through manipulation and disruption of the relationship with the caregiver,” says Branhouse.

Other adverse childhood experiences people may have include neglect, lack of resources and abuse, she adds.

To find a biomarker, a biological molecule in the brain that indicates early or normal puberty, Granata looked at the hypothalamus, as it is widely known to control when a person goes through puberty, among other important functions. p>

"There are cells that become activated and release certain proteins and peptides [hormones] that initiate puberty," says Branhouse.

Grenade found that these brain cells actually began to express and release these proteins earlier in female rats that had been separated from their mother. She identified a specific receptor—CRH-R1—in the hypothalamus that suppresses prepuberty and exposure to chronic stress.

"You can think of it as a constant battle between the 'go' signal and the 'stop' signal [in the brain]," says Grenade.

Stress hormones typically act as “brakes” on puberty because they cause the CRH-R1 receptor to suppress the release of hormones needed for puberty. Thus, they suggested that it is not just one stressful event, but chronic stress that weakens the “brakes” of puberty or reduces the sensitivity of the receptor to stress hormones.

This triggers a cascade of signals in the brain and body.

"Now all the 'go' signals get a free pass and say, 'It's time for puberty,'" says Grenade.

The hypothalamus releases specific hormones that tell the system to release the brakes and produce estrogen and testosterone, which are involved in the growth and maintenance of reproductive tissues.

Scientists did not observe accelerated puberty in male rats that were also separated from their mother.

To study the link between adversity and childhood trauma and anxiety in adolescents and adults, researchers used acoustic startles—bursts of noise that interrupt background white noise—in female rats after puberty. The experiment showed a significant negative correlation between age at puberty and the magnitude of the acoustic startle response, which is associated with disorders.

The rat that had earlier puberty, Granata says, experienced higher levels of anxiety during adolescence.

She hopes these findings can be used to potentially create interventions and treatments for girls who are at higher risk for anxiety and depression in adolescence and adulthood due to early puberty.