Definition: The hormonal cycle that occurs approximately once per month during a woman's childbearing years (beteen menarche and menopause). It is divided into two phases, each of which has different hormones which are more active.:
In the follicular phase, which lasts from the first day of the menstrual period (menses), called Day 1, estrogen dominates the cycle to stimulate an egg to mature. By the end of the phase, estrogen and androgens (male hormones) are at their peak. This period lasts an average of 14 days and ends with ovulation (release of the ovum (egg) from the ovary).
In the luteal phase, which lasts from ovulation until the next menstrual period (14 days), the hormone progesterone predominates. If, by the middle of this phase, fertilization has not occured, hormone levels begin to drop, and at the end of the cycle the lining of the endometrium begins to break down, ending in another menstrual period.
Pronunciation: MEN stroo al • (noun)
Common Misspellings: menstural, mensterul, mensteral
Charts and Graphs Illustrating Menstruation
Understanding Menstruation by Tracee Cornforth, About's Women's Health Guide
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