“Menopause is a point in time 12 months after a woman’s last period. The years leading up to that point, when women may have changes in their monthly cycles, hot flashes, or other symptoms, are called the menopausal transition, or perimenopause.
The menopausal transition most often begins between ages 45 and 55. It usually lasts about 7 years but can last as long as 14 years. During the menopausal transition, the body’s production of estrogen and progesterone, two hormones made by the ovaries, varies greatly. Bones become less dense, making women more vulnerable to fractures. During this period, too, the body begins to use energy differently, fat cells change, and women may gain weight more easily.”
NIH National Institute on Aging