Perimenopause causes
Perimenopause is a natural part of aging that happens when your ovaries gradually slow down and start producing fewer hormones.
During your reproductive years, your hormone levels—especially estrogen—follow a regular pattern each month. This process is guided by two key hormones: follicle-stimulating hormone (FSH) and luteinizing hormone (LH). FSH helps the ovaries grow follicles, which contain eggs and produce estrogen. Once enough estrogen is made, LH signals the release of an egg (ovulation).
After ovulation, the follicle continues to make estrogen and progesterone, which help build up the lining of your uterus. If you don’t get pregnant, those hormone levels drop, and your body sheds the uterine lining during your period.
When perimenopause begins, this cycle becomes less predictable. Hormone levels—especially estrogen—start to fluctuate, which can lead to irregular periods and symptoms like hot flashes, mood swings and sleep issues.