The menstrual cycle is, on average, 28 days and basically involves fluctuating estrogen and progesterone levels. Day one of the cycle is the first day of menstruation when estrogen and progesterone are at their lowest levels. I have never understood why doctors check hormone levels on day 1-5 because they are supposed to be low at this time. The first half of the cycle is known as the follicular phase, and it is the estrogen dominant part of the cycle


Estrogen peaks at approximately day 11-12 and this sharp increase in estrogen is what triggers the leutenizing hormone (LH) surge from the pituitary gland within the brain. Estrogen is responsible for building up the endometrial tissue in the uterus, so it is impossible to menstruate without estrogen production. Estrogen also causes one of the follicles in the ovary to become dominant and ready for ovulation. The rise in LH at approximately day 13 is what triggers ovulation. After ovulation, on approximately day 14, the corpus luteum starts producing progesterone. The corpus luteum is the remainder of the egg left behind in the ovary.

The second half of the cycle is thus called the luteal phase and it the progesterone dominant phase of the menstrual cycle. Progesterone levels peak approximately 6-8 days prior to the next menses and this peak occurs around day 21-22, when estrogen has their second peak in the cycle. Progesterone is responsible for stabilizing the thickened endometrial lining in the uterus. The purpose of the menstrual cycle is to ovulate and prepare the uterus for a pregnancy after conception takes place. If conception occurs, the corpus luteum continues to produce progesterone until 6 weeks after conception. The placenta then takes over the production of progesterone. If conception does not occur, the corpus luteum regresses, causing the progesterone level to fall. When the progesterone level gets back to its initial baseline, menstruation sets in and a new cycle is started. The only purpose of menstruation is to generate a healthy endometrial lining for implantation of an embryo.

A woman’s life can be broken down into four phases; premenarche, reproductive, perimenopause, and menopause. The average occurance of menarche, a woman’s first menstruation, is at 12.8 years of age. For the first year or two, the menstrual cycles are usually an ovulatory. Young women are producing estrogen, but not enough to produce the aggressive peak on day 11-12. As a result, the LH surge does not occur, resulting in an ovulation. If there is no ovulation, a corpus luteum is not produced, and thus progesterone is not made. These are estrogen dominant cycles, because even though estrogen levels are too low to ovulate, there is no progesterone to counterbalance the estrogen. An ovulatory cycles can result in amenorrhea or irregular menstrual cycles. Progesterone deficiency in young girls can result in mood changes that we see in perimenopausal women.

The cause of perimenopause is progressive follicular depletion. The age at which follicular depletion accelerates is estimated to be 37. Perimenopausal cycles behave exactly like the an ovulatory cycle described above. Just like in young women, they can have cycles of ovulation with episodes of an ovulation. The ironic thing is that a lot of perimenopausal women have 12-14 year old daughters who are experiencing the same cycle patterns. Perimenopause usually starts in the mid forties and lasts until menopause. Perimenopause is characterized by a decrease in the number of functional ovarian follicles and significant fluctuations in hormone levels. These fluctuations can be very dramatic from one cycle to the next and from day to day.

The decline in estrogen results in limited egg production, resulting in an ovulation and diminished progesterone production. An ovulation can result in irregular menses. Irregular menstrual cycles can consist of more frequent menses, longer or shorter menses, and heavier or lighter menstruation. It is common to have two or more menstruations per month, followed by skipping menstruations. Most gynecologists prescribe birth control pills, which will make the cycles regular again, but they will not alleviate the other symptoms of perimenopause, and often will make these symptoms worse. I believe in replacing the exact bioidentical hormones that are lacking.

Not only can women have irregular menstrual cycles, they can have other symptoms from lack of progesterone. The most common symptoms of perimenopause are mood disorders like depression and anxiety. These symptoms closely resemble symptoms of PMS, and the diagnosis of perimenopause is often made after women start to experience symptoms of PMS, which they may never have had before. This is a period of estrogen dominance, so the first line of treatment is to replace the missing progesterone. Not only can this regulate the menstrual cycle, but many of the mood changes like depression, irritability, anxiety and nervousness are alleviated as well. It is important to take only natural progesterone and not synthetic progestins, like Provera. Provera will regulate the menstrual cycle like birth control pills, but it will not help with the symptoms of PMS.

Estrogen levels are very unpredictable during perimenopause. They fluctuate dramatically throughout the day and they lack the predictable levels seen in a reproductive woman. To make matters worse, each cycle is vastly different from the previous cycles. Women may have no signs of estrogen deficiency one day and then be symptomatic the next day. Though perimenopause is a period of estrogen dominance, most women are also estrogen deficient. Perimenopausal women are still making estrogen, but not nearly what they were making in years past. The most common symptoms of estrogen deficiency are hot flashes, sleeping difficulties, and vaginal dryness. If these symptoms are present, estrogen supplementation is warranted.

Estradiol and progesterone should be checked via blood levels. It is important that your physician is able to interpret these levels because the laboratory will often give too wide a range of normal findings. I have found that symptoms will not improve until the progesterone is at least 2ng/ml. If the labs are normal and the patient is having symptoms, I will still treat them because it is ludicrous to treat lab values and not symptoms. A woman in perimenopause can still get pregnant, though it is more difficult than when she is in her twenties and thirties. The mean age of sterility is estimated to be 44.

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