Does menopause reduce estradiol and progesterone while raising FSH and LH?

Menopause marks a profound endocrine transition characterized by the functional exhaustion of the ovaries and a complete restructuring of the hypothalamic-pituitary-ovarian (HPO) axis.

Mechanistic cascade of follicular depletion

• Steroid hormone decline: The progressive depletion of the primordial follicle pool through atresia and ovulation exhausts the granulosa cell pool. Because these cells are the primary site of aromatase activity, their loss precipitates a sharp decline in circulating estradiol, which eventually stabilizes at low postmenopausal levels.
• Loss of progesterone: The exhaustion of functional follicles halts ovulation and prevents the formation of the progesterone-producing corpus luteum. Consequently, progesterone levels drop consistently. Following this depletion, peripheral conversion of ovarian and adrenal stromal androgens becomes the primary remaining source of circulating estrogens.

Disinhibition of the HPO axis

• Loss of feedback loops: During the reproductive years, estradiol and progesterone provide strong negative feedback to the hypothalamus and pituitary. Concurrently, ovarian-derived inhibin A and inhibin B act selectively at the pituitary level to suppress FSH synthesis and secretion.
• Gonadotropin elevation: The decline of these ovarian steroids and peptide hormones abolishes negative feedback, "opening" the feedback loop. This disinhibition increases GnRH pulsatility and pituitary sensitivity, causing a chronic, marked elevation of gonadotropins. Because inhibins are highly selective inhibitors of FSH, their early decline triggers an earlier monotropic rise in FSH, eventually resulting in a 10- to 20-fold postmenopausal increase in FSH alongside a 3-fold increase in LH.

Bottom line

• Ovarian follicle depletion during menopause directly reduces circulating estradiol and progesterone due to the loss of functional granulosa cells and the cessation of ovulation. This loss of ovarian steroid and inhibin negative feedback disinhibits the HPO axis, driving a dramatic and chronic elevation of circulating FSH and LH.