At birth, a female is endowed with approximately one to two million primordial ovarian follicles, each containing an immature egg. This number represents a woman's entire lifetime supply, as no new follicles are produced after birth. By the onset of puberty, the number of follicles declines to about 300,000 to 500,000 due to a natural process called atresia, where many follicles degenerate.

During perimenopause, a woman's body undergoes significant hormonal changes as it transitions toward menopause. This period is characterized by fluctuating levels of estrogen and progesterone due to declining ovarian function. Initially, estrogen levels can be erratic, with periods of high and low production, leading to irregular menstrual cycles.

Hormone Replacement Therapy remains the cornerstone of menopausal treatment. Understanding the use of exogenous hormones for the treatment of menopausal symptoms (Hormone Replacement Therapy (HRT)) is of critical importance to the health of women, especially given that women spend approximately 40% of their lives post-menopause.