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The Endocrinology of Perimenopause Current Topics in Menopause 55
anovulation, short luteal phase cycles, inhibin, anti-mullerian hormone, follicle
stimulating hormone, ovulation disturbances, bone loss, osteoporosis risk.
INTRODUCTION AND BACKGROUND
As early as 1871, Tilt described the perimenopause as “a turbulent time for women’s
reproductive organs” [1] (p. 220). Only after the 1980s however, was the distinction
made between the life phase that begins one year after the last menstrual flow (now
called menopause, or redundantly [post]menopause) and the menopause transition,
also known as the “perimenopause” [2]. Social scientists like Neugarten and
Kraines, noted that the experiences during the menopause transition and menopause
were quite different. In the 1960s these researchers systematically questioned
adolescents, premenopausal women, women in the menopause transition (who had
irregular cycles) and menopausal women. They found a striking resemblance
between symptoms in adolescent women and women in the menopause transition,
with the least symptomatic women being those who were menopausal (meaning
older midlife women who were one year since their last menstruation) [2].
After estradiol was discovered in the 1920s, it became common to attribute
problems in older women to “estrogen deficiency”. For many decades since then
it was understood that estrogen levels dropped gradually through the menopause
transition from premenopausal levels to menopausal levels.
By the 1990s, it became recognised that the hormonal changes occurring before
and during the menopause transition were highly complex and could involve both
higher and lower than normal premenopausal levels of estradiol, and sometimes
lower than normal ovulatory cycle progesterone levels [3-5]. Although it is clear
that significant hormonal changes occur with the onset of irregular cycles that are
characteristic of the early menopause transition, many women start to experience
symptoms before this in what the Stages of Reproductive Aging Workshop
(STRAW) calls late reproductive age. Thus there may be significant hormonal
changes occurring before the menopause transition officially begins.
Although skipped periods and irregular cycles are characteristic of the menopause
transition (STRAW criteria for entry into the menopause transition), in fact many
of the midlife symptoms such as breast tenderness and heavy menstrual periods