Progesterone is one of two main hormones that allow the female glandular system to function properly. The opposing hormone of Progesterone is Oestrogen. Both hormones are manufactured in the ovaries (and smaller amounts in the adrenals) of menstruating women. These two hormones are antagonistic to each other, yet work as a team to create hormonal regulation. Progesterone has a balancing effect on excessive Oestrogen and is also a precursor to Oestrogen, Testosterone and the cortical steroids.
Progesterone is made from cholesterol into a sterol called Pregnenolone, which is the precursor to Oestrogen. This is a hormone which is dependant on ovulation and the development of the Corpus Luteum (luteal phase of the cycle) for its production. Due to ovulation rates declining during the peri-menopausal years, the amount of Progesterone present also begins to decline. In those cycles where ovulation fails completely, Progesterone levels are negligible.
When a woman’s cycle is functioning correctly Oestrogen is the dominant hormone during the first two weeks of the menstrual cycle. In response to ovulation, Progesterone assumes dominance for the final two weeks of the month. When the Pituitary gland in the brain sends a message to the ovaries to stop the production of Progesterone, the menstrual cycle begins within 48 hours of this message.
Due to ovulatory cycles, Progesterone levels typically decline before menopause starts and this is followed by a decline in Oestrogen. Progesterone tends to fall to almost zero while oestrogen declines to a bout 40-50%. This situation leads to an imbalance between Oestrogen and progesterone causing an increase in oestrogen activity which is commonly described as oestrogen dominance.
Progesterone production is reliant on ovulation (luteal phase of the cycle) and the development of the corpus luteum. With the decline in ovulation during the process of a women moving from her fertile years to non-fertile years, the biological changes that take place with oestrogen also occur with progesterone.