Perimenopause can begin eight to ten years before menopause, when the ovaries produce less estrogen and progesterone. It usually starts in a woman’s 40’s, but can start in the 30s as well. Perimenopause lasts up until menopause, the point when the ovaries stop releasing eggs. In the last one to two years of perimenopause, the drop in estrogen and progesterone accelerates. The estrogen levels rise and fall unevenly during perimenopause. As progesterone also decreases towards menopause as it is produced only if an egg is released.
Lack of progesterone can result in irregular, heavier, and prolonged menstrual periods during perimenopause. During this transition phase to menopause, FSH levels tend to fluctuate and go up and down. FSH levels can be very high one day and very low the next day. When FSH levels are high, the ovaries make more estrogen. When FSH levels drop, estrogen levels drop. These changes in FSH and estrogen can happen months to years before menopause.
