When we’re first taught about our cycle, we often only learn about our period. While that’s an important part of the cycle, it’s actually only a small part of it!
In reality, the cycle is the month-long process of preparing the body for pregnancy. One of the main events during the cycle is ovulation – but what exactly is ovulation and when does it occur? Keep reading to find out!
Importance of Ovulation
Regular release of an egg, a.k.a. ovulation, is a sign of health in tons of ways outside of reproductive health.
When ovulation is regular estrogen and progesterone take turns influencing the brains. Estrogen stimulates brain cells while progesterone maintains and heals them. Healthy ovulation and hormonal patterns helps optimize brain development during puberty, maintenance of cognitive function in perimenopause, and may even play a role in preventing anxiety, depression, and other mood disorders.
Did you know that bone is a dynamic tissue, subject to change based on environmental, lifestyle and even genetic factors? Estrogen encourages bone formation while progesterone that comes from our ovary after ovulation promotes maintenance of bone mineral density.
With healthy ovulation, estrogen, which tends to raise blood sugar levels, is balanced by progesterone, which normalizes blood sugar.
What happens to your body when you ovulate?
A follicle is a fluid-filled sac that houses an immature egg. Every baby girl has 100s or 1000s of follicles at the moment of birth, each containing an immature egg. (Actually, she probably had them several weeks prior to birth!)
At puberty, a girl will mature into a woman of reproductive age. Follicular growth is a key step in this maturation with ovulation being a sign that she is maturing healthfully. Follicular growth is spurred on by a hormone called follicle-stimulating hormone (FSH).
At the base of the brain there is a pea-sized gland called the pituitary gland. At the beginning of every cycle, even while menstruation may still be occurring, the pituitary sends out FSH to start follicular growth in the ovaries.
As the follicles grow, they will make more and more estrogen. Rising estrogen levels will tell the brain to shut off FSH and move on to the next phase of the cycle.
As women age, our store house of eggs gradually reduces. This natural reduction in “ovarian reserve” means the brain needs to send out more FSH to accomplish the same extent of follicular growth. This is how knowing your FSH levels – always measured at the beginning of your cycle – can provide insight into your egg reserve.
As the recruited follicles grow they make more and more estrogen. Rising estrogen, specifically estradiol, is one way we know we are approaching the main event of the cycle – ovulation!
Luteinizing Hormone (LH) Surge
When estrogen reaches its highest level (peak), the pituitary sends down another hormone that, along with progesterone, helps the biggest follicle to release its egg. This hormone is luteinizing hormone (LH) and it’s known as the ovulation predictor hormone.
A sharp rise in LH means ovulation should occur in the next 24-36 hours. You cannot ovulate with LH.
Note: It is possible to have a rise in LH and not ovulate. For reasons we are still trying to understand, this can happen in women with PCOS.
Release of the Egg
Hurray for ovulation! An egg that is released from an ovary will make its way into the safety of the fallopian tube where it will hang out for 12-24 hours.
On the other end of your reproductive tract, if intercourse occurs, sperm will need to swim through the cervical canal, the uterus, find the opening to the fallopian tube and traverse it. (This generally happens within minutes of ejaculation.)
Conception – the meeting of sperm and egg – occurs in the fallopian tube.
Remember that big follicle that got to release its egg? After ovulation it gets a makeover and becomes a new mini organ called the corpus luteum. Ovulation starts the transformation of the follicle into the corpus luteum.
The corpus luteum mostly produces progesterone, the hormone that rises after ovulation and prepares the uterus for implantation – which will occur if an egg was fertilized. “Successful” ovulation only occurs when an egg is released and progesterone levels remain elevated during the implantation window.
From brain health to bone health, ovulation plays a key role in women’s health and fertility.