An analysis of chemicals that could involuntarily activate parts of the brain responsible for reproductive functions has identified compounds that many of us may encounter in our environment, highlighting a potential trigger for early puberty in women.
One of these is a musky flavor once commonly used in men’s perfumes that has been banned by the European Union but can still be found in products sold in much of the world, including the US.
Over the past century, the average ages of menarche – the start of menstruation – and breast development have trended downward. While there are obvious racial and socioeconomic factors, the phenomenon is too global and too rapid to be entirely genetic, leaving scientists to wonder what new environmental factors might be causing such early changes.
Although numerous studies have looked for candidates that could explain , inconsistent results have made it difficult to identify the culprits. Many observational studies are also limited by their methods, only being able to collect blood and urine samples from volunteers during waking hours.
Researchers from the US National Institutes of Health and North Western University chose to focus their research on a network of neurons in the hypothalamus known to play a critical role in managing the onset of puberty.
A musky scent once used in men’s perfumes
Gonadotropin-releasing hormone (GnRH) neurons stimulate the pituitary gland to secrete several chemical cues, which in turn tell the ovaries to produce estrogen and the testes to pump out testosterone, he writes.
Although the mechanisms behind this process are not fully known, a neuropeptide called kisspeptin is believed to be involved. In addition, the nerve cells that produce the neuropeptide have their own receptors that sensitize them to changes in stress and diet, making this a perfect place to start looking for other forms of interference.
Instead of looking for signs of disruption in a sample of volunteers, the researchers used a tissue culture grown in the lab to look for the effects of different substances on the cells’ GnRH and kisspeptin activity.
The screening itself was substantial, sifting roughly through an Environmental Protection Agency library. Then, additional assessment tools whittled the list down to dozens of compounds that interfered with one or both pathways.
The substance is less common in commercial products today
Among the substances tested were types of cholinergic agonist, a group of chemicals that mimic a transmitter common to a variety of neural pathways responsible for memory, motivation and arousal.
One compound in particular stood out – a candidate agonist for kisspeptin called ambrette. This sweet, slightly animalic flavor was banned by the European Union in the 1990s following evidence of its neurotoxicity in rats, although it continues to be synthesized in India and China.
The substance is less common today, thanks to the recommendations of the International Perfume Association. But being resistant to degradation, it continues to be present in the environment, which could be a serious and ongoing concern, studies like this one warn.
Further testing of musk ambergris on human and mouse hypothalamic cells in culture and on zebrafish further demonstrated the scent’s potential to stimulate parts of the brain to produce cues that could trigger puberty at earlier ages.
This research was published in
