Perimenopause is the “around‑menopause” phase when the ovaries begin to wind down and the brain tries to figure out what happens nextmayoclinic.org. In medical terms it’s a transition rather than a disease: estrogen and progesterone production fluctuates wildly as the ovaries age, leading to unpredictable menstrual cycles and sporadic. 
 
This isn’t a short blip – perimenopause can begin eight to ten years before the last period, often in the mid‑40s but sometimes as early as the mid‑30smy. On average it lasts about four years, though it can persist for only a few months or stretch to eight years.
 
Follicle‑stimulating hormone (FSH) levels, which help drive ovulation, begin to rise roughly six years before the final menstrual period and fluctuate as estrogen.  These hormonal changes can make you feel like you’ve been dropped back into an adolescence you never asked for, except the aim this time is to wind down fertility.