Comprehensive Epilepsy Center
Women's Health - Menstrual Cycle 

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The major female hormones are estrogen and progesterone. The ovary is the main site of production of these hormones. These hormones are made from cholesterol.

Estrogen:
Estrogen is released by the ovary in response to follicle-stimulating hormone (FSH), a signal that is released by the pituitary gland in the brain.

There are three main forms of natural estrogen in humans- estradiol, estrone, and estriol. During pregnancy, estrogen is made in large quantities by the placenta.

There are also synthetic forms of estrogen-one of the highly potent forms is ethinyl estradiol. This form is widely used in birth control pills.

Estrogens are largely responsible for the changes that occur in women at puberty-enlargement of the breasts, growth and development of the vagina and uterus, and also shape the skeleton.

Progesterone:
The formation of progesterone by the ovary is regulated by leutinizing hormone (LH), a signal which is released by the brain from the pituitary. Progesterone is also secreted during the second half of the menstrual cycle and in pregnancy by the placenta.

There is only one form of natural progesterone. There are many forms of synthetic progestins-medroxyprogesterone (depo-provera), norethindrone, norgestrel, megestrol acetate (megace). Some are actually made from testosterone (the major male hormone).

Abrupt decline of progesterone at the end of the menstrual cycle causes bleeding.

The Menstrual Cycle:
There are four main phases of the menstrual cycle: follicular phase, ovulatory phase, luteal phase, and menstrual phase. The first half of the menstrual cycle is the follicular phase. Levels of estrogen increase.

At mid-cycle with ovulation, LH is released from the brain. The LH surge usually lasts 48 hours. This leads to a drop in estradiol and an increase in progesterone.

The second half of the cycle is the luteal phase. Progesterone is the dominant hormone. If the egg is not fertilized, it begins to die. This leads to a drop in progesterone and estradiol. Menstrual bleeding then begins.

For women with epilepsy, especially temporal lobe epilepsy, as many as 1/3 of menstrual cycles are anovulatory. That is, no egg is released (pregnancy cannot occur). With anovulatory cycles, progesterone is not released during the second half of the menstrual cycle.

Effects of Hormones on Seizures:
The sex hormones have complex interaction with the main cells (neurons) of the brain. Estrogen activates seizures. If estrogen is applied to an animal’s brain directly, the animal will have a seizure. Progesterone has the opposite effect and actually protects against seizures.

This may explain why some women note that their seizures are linked to their menstrual cycle. This is called catamenial epilepsy. Some women have seizures mid-cycle at the time of ovulation (estrogen levels are high) and others note increased seizures just before and during bleeding (progesterone levels are dropping rapidly). With anovulatory cycles, progesterone is not secreted in the second half of the menstrual cycle. Seizures may occur throughout the last two weeks of the cycle.

To determine if your seizures are linked to your menstrual cycle, keep a calendar of your seizures and menses for at least three months and then show it to your doctor. You could also try to determine if you are ovulating with each cycle by having a Day 22 progesterone level checked. If it is more than 5, then you did ovulate. It may be very difficult to determine if you seizures are linked to menses, if you do not know if you are ovulating.

Treatment of Catamenial Seizures:

1. Medication Adjustment
   Many women benefit by taking additional medication at or before the time of expected increase in seizures. You need to talk to your doctor about this option.
2. Hormones
   There are research studies that are looking at various forms of both synthetic and natural progesterone to determine if progesterone will decrease seizures. There have been a few published studies with a small number of women that are encouraging. Hormonal studies must be done together with a gynecologist and certainly cannot be done in women that are trying to become pregnant.