Everyone’s hormonal — meaning we all have progesterone, estrogen, and testosterone swirling around in our bodies in different amounts. Males are dominated by testosterone, the levels of which vary throughout the day. Females predominantly produce estrogen and progesterone, and those levels vary throughout the month according to their menstrual cycle, if they still have one.

The female hormonal cycle that controls reproduction is intuitive and can guide a woman’s sexual and social decisions, writes UCLA psychology professor Martie Haselton in her new book Hormonal: The Hidden Intelligence of Hormones. These biological messengers can signal when it’s time to mate, make us feel more social, and can help a new mother bond with her infant.

From menstruation to menopause, Haselton encourages women to get to know their female biology (hormones intact). Here are some interesting facts about our not-so-hidden hormones we found interesting.

Women’s menstrual cycles don’t sync
Normal cycles can vary in an individual from month to month. Since a normal menstrual cycle is anything from 21 to 35 days, it makes sense that at some point, you would have an overlapping period with your sister, roommate, or coworker. There might be a perception that you’re syncing up, but there’s actually no evidence that menstrual synchrony is real.

Speaking of periods…
There are a lot of factors unrelated to pregnancy that can cause menstrual irregularity. Physical and emotional stress, along with drastic weight loss or weight gain, exposure to environmental toxins, and breastfeeding, can all disrupt your “regular” cycle.

Ovulation isn’t completely concealed
Even though women don’t broadcast peak fertility physically, research shows there are tell-tale signs of ovulation. At high fertility — when we’re about to ovulate — women are more likely to wear red and pink, and their body odor is more pleasant to men.

A woman’s voice can also change as she approaches ovulation. It might not be noticeable to the casual observer, but when Haselton and her colleagues recorded vocal samples of close to 70 women, they noticed that the pitch of the women’s voices rose when they were close to or at peak fertility. (However, there appears to be no vocal change evident in those on hormonal contraception). In a different study, male and female “voice raters” judged the higher-pitched recordings as more attractive than those at low-fertility. This might be because a higher voice is perceived as more feminine, writes Haselton.

Pregnancy changes the brain
Up to 80 percent of new mothers report memory problems. Research has found that with an increase in parity (the more kids a woman has) there’s a decrease in gray matter associated with tasks like verbal recall.

This might sound concerning, but it seems the brain is changing in an important way that helps foster bonding between a mother and her newborn. This change wasn’t noticed in fathers. And while a new mother may have a little trouble remembering what that thing was called, her brain is helping her adapt to the role of motherhood.

Pregnant women also show an increase in “nesting” — creating a safe space for their new infant — and new mothers demonstrate a heightened sensitivity to protect their young. A breastfeeding woman experiences a decrease in stress but an increase in aggression when a threat is detected.

Menopause may help women tolerate children who aren’t theirs
Haselton proposes that living past our reproductive years provided a way for ancestral females to remain productive; a grandmother helping care for the next generation would ensure their genetic legacy, she writes. In one study, women ages 53 to 60 were drawn to a wider range of “cute” baby faces compared to younger (likely fertile) women. This could “offer an evolutionary assist” as menopausal women embrace offspring that aren’t their own, writes Haselton.

We can learn from our hormones
Some argue that any biological explanation linked to a woman’s behavior only keeps her from achieving and enforces gender stereotypes — whether in or out of the home — writes Haselton, who adds that researchers like her have been urged to keep information about women’s hormones and their behavior out of the mainstream.

Women aren’t totally controlled by their hormones, but they can learn something from them. Acknowledging the biological effects hormones can have on a woman’s body won’t hold her back, it will only empower her to make more informed social and reproductive decisions backed by science. Haselton argues more hormonal knowledge is an empowering step that can sharpen the focus on women’s health issues throughout all stages of life.

Keri Wiginton is a writer and photographer focusing on issues related to women's health, mental well-being, and feminism. Her work has appeared in the Chicago Tribune, Washington Post, Austin-American Statesman, Tampa Bay Times and Houston Chronicle. Follow her work at www.keriwiginton.com or on Twitter at @keriphoto.