Beginning at puberty, a woman's ovaries start releasing estrogen in coordination with each monthly menstrual cycle. At mid-cycle, levels suddenly spike, triggering the release of an egg (ovulation). They then fall just as quickly. During the rest of the month, estrogen levels climb and fall gradually.
Normal estrogen levels vary widely. Large differences are typical in a woman on different days, or between two women on the same day of their cycles. The actual measured level of estrogen doesn't predict emotional disturbances.
Hormones and the Brain
That's not to say estrogen isn't a major player in regulating moods. Estrogen acts everywhere in the body, including the parts of the brain that control emotion.
Some of estrogen's effects include:
Increasing serotonin, and the number of serotonin receptors in the brain.
Modifying the production and the effects of endorphins, the "feel-good" chemicals in the brain.
Protecting nerves from damage, and possibly stimulating nerve growth.
What these effects mean in an individual woman is impossible to predict. Estrogen's actions are too complex for researchers to understand fully. As an example, despite estrogen's apparently positive effects on the brain, many women's moods improve after menopause, when estrogen levels are very low.
Some experts believe that some women are more vulnerable to the menstrual cycle's normal changes in estrogen. They suggest it's the roller coaster of hormones during the reproductive years that create mood disturbances.
Estrogen and Premenstrual Syndrome (PMS)
As many as 90% of women experience unpleasant symptoms before their periods. If symptoms are reliably severe enough to interfere with quality of life, it's defined as premenstrual syndrome (PMS). Generally speaking, PMS is present when:
Physical and emotional symptoms occur reliably a few days before multiple consecutive menses (periods).
The symptoms go away after completing a period and don't occur at other times.
The symptoms cause significant personal problems (such as at work, school, or in relationships).
No medicines, drugs, alcohol, or other health condition might be to blame.
Bloating, swelling of arms or legs, and breast tenderness are the usual physical symptoms. Feeling overly emotional, experiencing depression, anger and irritability, or having anxiety and social withdrawal may be present. As many as 20% to 40% of women may have PMS at some point in life.