14 DAY TRIAL // What's the link between human puberty hormone and the love outbursts in hamsters?
It seems that they are regulated by the same hormone.
An American team found a connection between the kisspeptin hormone and how animals interpret seasonal environmental signal, like day length, to tune their reproduction when conditions are optimal.
"Studies in humans have shown that individuals with deficits in the receptor for kisspeptin have severe reproductive impairments," said study team member Gregory Demas of Indiana University in Bloomington.
The Centers for Disease Control and Prevention (CDC) report that fertility rates in the United States decrease in autumn but a link between this human situation and kisspeptin is still to be proven.
"In humans and other species, if the environment is not satisfactory, sex drive will decline; kisspeptin is likely part of the pathway responsible for this regulation," said team member Lance Kriegsfeld of the University of California, Berkeley.
Siberian hamsters breed intensely in summer and experience a decline as winter approaches and that's why the researchers chose this species.
The team put Siberian hamster (Phodopus sungorus) males into two treatment groups: one housed in summer-like conditions with 16 hours of light daily, and other in winter-like conditions with 8 light hours daily.
Eight weeks later, kisspeptin level in the second group markedly dropped in a brain region controlling reproduction and sex behavior, compared to hamsters from the first group.
In summer light condition, the individuals had much heavier testes, higher body weights and more testosterone compared with their short-day cousins.
In another test, individuals kept in winter or summer conditions for eight weeks were given a shot of kisspeptin.
The winter hamsters were just as responsive to kisspeptin as the summer ones, presenting the same increase in the level of luteinizing hormone.
Thus, kisspeptin turns on the reproduction even in winter "signaling".
In humans, kisspeptin is linked to the release of luteinizing hormone, important to puberty and other sex-related functions.
In women, an increase in this hormone starts ovulation, whereas in men raises testosterone production.
The team will investigate if temperature plays any role in this hormonal signaling.
"Perhaps, there are human counterparts to these factors, including stress and malnutrition that regulate the hormone and human reproductive success."