PMDD

Causes of Premenstrual Dysphoric Disorder (PMDD)

File photo. | Credit: Women's Health Opens in new window

Each woman’s experience of the physical aspects of monthly menstruation is different. We all know that some women’s periods are longer or shorter than our own; that the flow of blood may be heavier or lighter; and that cramping may be stronger, weaker, or nonexistent.

Similarly, the very real effect of monthly cycling on emotional and physical premenstrual symptoms differs from woman to woman, as well.

Most women have a few minor, tolerable complaints just prior to their periods—perhaps a little bloating, increased moodiness, breast tenderness, insomnia, or cravings for certain type of foods.

These are natural responses of the body to the hormonal and other physiologic changes that occur in all women of childbearing age. Between 20 and 40 % of women have moderate premenstrual complaints, with symptoms that are more uncomfortable, distressing, or annoying than the average, but that are still tolerable and don’t affect the way these women function or relate to people. These women are said to have premenstrual syndrome (PMS)Opens in new window, a diagnosis that acknowledges that changes are occurring and that the discomfort is not merely in these women’s minds.

This diagnosis recognizes the overwhelming and sometimes debilitating physical, mental, behavioral, and emotional responses a woman may have in the ten to fourteen days prior to menstruation, and which disappear entirely within a day or two after menstrual bleeding begins.

No one knows why some women have certain symptoms or more intense symptoms than other women have. Physicians don’t know whether PMDD reflects an extreme of the normal range of expected symptoms, or if there is some other underlying problem — or set of problems — that causes a more intense reaction of the body to premenstrual changes. Research hints that the latter might be true. Before before we can begin to talk in detail about what happens in the body to cause PMS, PME, or PMDD, we need to have a basic understanding of what happens in a typical menstrual cycle.

The Physiology of the Menstrual Cycle

Few of us really consider the exquisite timing and coordination required by the body to bring on monthly menstruation. Most people know the basics of a typical menstrual cycle: Every month, a woman’s body produces a mature egg.

When the time is right, the egg is released from a sack (or follicle) in an ovary, a process called ovulation. The egg travels down the fallopian tube to the uterus.

It all seems to happen somewhere “down there” in the body. But when we look at the details, we see that menstruation occurs only because of an intricate communication system between the brain and the reproductive organs, with all messages in the communication system carried by hormones.

Hormones are complex chemicals that are produced in various organs of the body, travel through the bloodstream to other organs, and signal that some action needs to take place. Interestingly, hormones are produced in response to signals from other hormones, and sometimes hormones are produced because of the lack of another hormone, so there is a constant give-and-take of hormonal messages in the body. Menstruation requires and is guided by five major hormones that carry communication between the brain, the pituitary gland, the ovaries, and the uterus.

The average menstrual cycle lasts twenty-eight days, although “normal” cycles can run from twenty-one to thirty-five days. The following description assumes a twenty-eight-day cycle.

Day 1 of a new cycle starts the day menstrual bleeding begins. Starting at Day 1 and continuing to about Day 14 is the follicular phase of the menstrual cycle.

In the follicular phase, a portion of the brain called the hypothalamus releases a hormone called gonadotropin-releasing hormone (GnRH).

Gonadotropin-releasing hormone sends a message to the pituitary gland (located at the base of the brain), which releases follicle-stimulating hormone (FSH). Follicle-stimulating hormone travels through the blood-stream to the ovaries where it stimulates the growth and maturation of eggs in little sacks called follicles (hence the name follicular phase).

Although many eggs may start ripening, usually only one outpaces the others and becomes a mature egg. The arrival of the FSH hormone messenger also prompts the ovaries to produce estrogen, one of the two primary hormones responsible for “femaleness.” This estrogen enters the bloodstream and signals the uterus to start the process of thickening the lining in preparation for the mature egg.

The rising level of estrogen in the blood is detected by the pituitary gland. This signal prompts the pituitary gland to do two tings:

1. Cut back on its secretion of FSH (the job of that hormone is virtually done because the follicle is nearing full maturation); and,
2. Secrete luteinizing hormone (LH), which causes the mature egg to be released from the follicle. The release of the egg, known as “ovulation,” occurs at about Day 14. This begins the portion of the menstrual cycle known as the early luteal phase, from about Day 15 to Day 21.

The empty follicle (now called the corpus luteum, which gives the luteal phase its name) starts producing estrogen and large amounts of progesterone, the other primary hormone responsible for femaleness. The rising levels of both estrogen and progesterone in the bloodstream signal the uterus to continue to build and thicken the uterine lining. Additionally, when the pituitary gland senses the high hormone levels, it stops secreting FSH and LH.

The corpus luteum needs FSH and LH to continue to work, so when circulating levels of these hormones fall, the corpus luteum begins to disintegrate and stops producing estrogen and progesterone. Once estrogen and progesterone levels begin to fall, we enter the late luteal phase of the menstrual cycle, when premenstrual symptoms occur. This occurs about Day 22 to Day 28.

Without a steady and abundant supply of estrogen and progesterone, the uterine lining cannot be maintained. It separates from the uterus and appears as menstrual blood. On Day 28, just before bleeding starts, estrogen and progesterone levels are at their lowest. The low levels of these hormones are detected by the hypothalamus, which responds by secreting GnRH, and the cycle begins again.

Theories About What Causes PMDD and PMS

As is probably obvious from the description of a typical menstrual cycle, there are a multitude of factors that have the potential to cause or contribute to premenstrual symptoms. And if the picture doesn’t seem complicated enough yet, consider this:

Through decades of research, scientists have come up with various theories or models to explain what might be happening in the body to cause premenstrual symptoms. These models provide scientists with a place to begin, a way to think about the problem, which allows them to formulate experiments that can test out the limits of the model.

Each experiment provides one small piece to the puzzle, and it is hoped that, when all the pieces are complete, a full image of PMDD will emerge. Today, the model that best fits the available data is that PMDD is a function of biochemical changes in the brain secondary to fluctuating levels of ovarian hormones (estrogen and progesterone).