This week, we are going to do something a little different. As women, it’s important that we understand how our bodies work, especially hormones. It just doesn’t seem fair that we go around blaming our hormones every month without much understanding of them. By now, your hormones may quite possibly be muttering “but you don’t even know me”, every time they are deemed the culprit for menstrual cramps or weight gain. Well, yes, they very well are the culprit, but at least now you know why. So, this week, we are arming you with the knowledge of your very own body and its reproductive hormones. Welcome to Female Hormones 101.
The moment you are born, you are equipped with all the eggs you will ever have. This means that, yes, it’s only all downhill from here. Eggs are stored in the ovaries and overtime, these eggs will naturally degrade and become lost and once a month beginning in puberty, one egg is released. As a girl ages, a gland in her body called the pituitary gland will gradually produce more and more of two different hormones that go and stimulate your ovaries. When this occurs, each egg in your ovary will develop its own little sack called a follicle. Once a month, several follicles will begin to mature. It’s a fight for the strongest egg. Whichever egg is most mature will go on to be ovulated and the others will simply be lost. This process of egg loss continues until a woman runs out of eggs at which point she goes through menopause.
All of these events described above are hormonally and genetically driven, yet still able to be influenced by your environment. Hormones are molecules that act as small messengers in your body, carrying messages to different cells in order to change their function. For example, the hormone, insulin, is secreted by pancreatic cells. Insulin changes the function of your blood cells by allowing them to take sugar floating around in the blood and contain it within their cellular structure. All hormones work in a similar way, they are produced in one area, migrate to where they will cause an effect, and then cause that effect. They are produced only as they are needed.
The female reproductive system, which is responsible for your menses each month, is a complex process that is driven and regulated by hormones in communication between the brain and ovaries. There are five main hormonal players in your reproductive system: GnRH, LH, FSH, Estrogen, and Progesterone. (GnRH - gonadotropin releasing hormone, LH - leutenizing hormone, FSH - follicle stimulating hormone). Your reproductive parts are not the only players here. There are also three other body parts involved in female reproduction: the hypothalamus, pituitary gland, and your ovaries. Now we’ll get a bit more detailed.
The hypothalamus is a region at the base of the brain that has several important functions including controlling thirst, hunger, sleep patterns, libido, and of course, reproductive processes. The hypothalamus produces the hormone GnRH regularly every 1 to 2 hours and will stop producing GnRH in response to your body’s estrogen and progesterone levels.
After its release, GnRH will make its way to your pituitary gland, located just below the hypothalamus. The pituitary gland will respond to GnRH by producing two hormones, FSH and LH.
FSH and LH are two important hormones in the female reproductive system secreted by the pituitary gland, which sits just below the hypothalamus, waiting for messages. FSH and LH are both released when GnRH stimulates the pituitary gland. FSH and LH then move to the ovaries where they cause their effect. Once there, they stimulate the ovaries to produce estrogen and also help with growth and maturation of your eggs. On about day 14 of your cycle, LH levels will suddenly spike (we’ll explain more about why, below). This is what causes ovulation each month. After this, LH also tells your ovaries to produce progesterone. After day 14, your LH levels will slowly fall and return to normal again.
Estrogen: the hormone that comes to mind when most people think about the female reproductive system, and for good reason. Estrogen is an important female hormone produced by the ovaries that is involved with the female reproductive system and several other important bodily functions. In addition to its role as a sex hormone, Estrogen also plays a role in bone and muscle growth, maintaining the lining of the uterus, maintaining your feminine characteristic. During the menstrual cycle, Estrogen levels increase after FSH and LH are produced by the pituitary and stimulate the ovaries. After this, once Estrogen is produced, the high levels of Estrogen in your blood will cause your FSH levels to decrease. Strangely, however, as Estrogen reaches higher and higher levels, suddenly, your LH levels will peak as well in response to this rising estrogen. This sudden surge in LH is what causes ovulation each month. So, as you can see, Estrogen and LH important partners in your menstrual cycle, each is responsible for the rise of the other.
Progesterone is most important in your menstrual cycle during the last half of the cycle, from day 14-28. Progesterone is made in the ovaries in response to LH, but only increase after ovulation and peaks on day 21 of your cycle. Progesterone is responsible for communicating the the hypothalamus that enough GnRH has been made and therefore, GnRH levels decrease in response to Progesterone. Progesterone is also works with estrogen to build up the lining of the uterus so that a fertilized egg has a nice, cushiony spot to implant. Estrogen is responsible for making the lining thick, while Progesterone is necessary to stabilize the lining of the uterus so that the egg does not just slough off. If no egg is fertilized after ovulation, a small structure left over from the egg, called the corpus luteum, will begin to slowly break down and cause Progesterone levels to decrease. As Progesterone levels decrease, the fluffy uterine lining you built will shed. This shedding of the uterine lining is the blood you see each month during your menses! Once progesterone levels have fallen significantly, the hypothalamus will no longer be receiving a “no” from progesterone and therefore, GnRH will increase which will then lead to FSH and LH to increase. And, we are back to square one.
This is a great video that easily explains and illustrates the complicated process of the female hormones in context of the menstrual cycle. I recommend it for anyone to watch. It’s a great learning tool. https://www.youtube.com/watch?v=2_owp8kNMus
The female reproductive system is one of the most complex bodily systems, so it’s no wonder many people don’t learn it during their brief sex ed course in high school. It is my belief, however, that women should have at least a general understanding of the function of their hormones. Female hormones are always rising or falling. Some spike while others remain stable. Our reproductive system is complicated, yet beautiful and so important for all human life. In understanding the complexities of female hormones, perhaps we can better understand the complexity of women themselves. Several problems arise in women when one or more hormones are not functioning properly. Issues such as infertility, polycystic ovarian syndrome, premenstrual syndrome, and so many more are a result of improper hormone levels. Hopefully this week, we were able to aid you in gaining some insight about your own body and help you learn to love your complex nature.