杏吧原创

Female reproductive hormones cycle daily as well as monthly, a small study suggests. The finding may help explain why some women experience daily mood fluctuations.

It is well-established that women鈥檚 reproductive hormones like oestrogen, progesterone, follicle stimulating hormone (FSH) and luteinising hormone (LH) follow monthly cycles to help prepare their uteruses for pregnancy.

Steven Lockley at Harvard University and his colleagues wondered if these reproductive hormones might follow daily cycles as well, based on similar findings in mice and rats.

To find out, they measured hormone levels in 17 women every 2 hours for nine days.

They discovered that the women鈥檚 oestrogen, progesterone, FSH and LH levels followed regular cyclical patterns each day in the first part of their menstrual cycle leading up to ovulation, while only FSH continued to do so after ovulation.

This suggests that daily hormone rhythms are responsible for controlling the time of day of ovulation, the researchers write.

Getting the timing right

Female rodents also have a daily hormone cycle, which is thought to optimise their chance of getting pregnant by making sure the time of day they ovulate coincides with when they feel most motivated to have sex.

The reason why women have a daily hormone cycle may also be to encourage sex at the time of day they are most fertile, but this needs further investigation, says Beverley Vollenhoven at Monash University in Australia.

This was only a small study, conducted over a short period of time, so further research is needed to confirm the team鈥檚 findings.

But if their discovery holds up, it may explain why female shift-workers tend to have more problems conceiving than other women, says Vollenhoven. Working at night is known to disrupt circadian rhythms, which could in turn deregulate daily hormone patterns and mess with the timing of ovulation and sexual arousal, or suppress ovulation altogether, she says.

The daily hormone cycle may also explain why women鈥檚 moods vary at different times of the day, says Jayashri Kulkarni at Monash University. For example, one study of female university students found that their happiness , drop sharply at 2pm, lift again at 3pm, then gradually decline until they went to bed.

鈥淲e know that all of these so-called reproductive hormones have really significant effects on brain chemistry,鈥� says Kulkarni. For example, the hormones oestrogen and progesterone can interact with brain chemicals like serotonin and dopamine that regulate mood and emotion, she says.

Research suggests that men also have hormone cycles that affect mood and fertility. Men鈥檚 happiness has been found to be 补苍诲听迟丑别颈谤 .