If you are taking progesterone as part of the hormone replacement therapy for menopause, there may be some facts about progesterone that you are not aware of.  Prescribing progesterone has become controversial.  Do you need it at all?  How much is adequate?  Should you have blood levels checked or saliva tests?  What application is best; cream, patch, gel, oral pill?  This article will address some of these questions.

To understand a hormone, let’s look at the way it would work in nature.  Progesterone is excreted by the ovary; actually by the structure in the ovary which houses the egg.  After ovulation, this structure (corpus luteum), turns into a progesterone producing factory.  Serum levels of progesterone spike up and remain elevated for 12 days exactly.  Then, the structure stops production and the levels sharply fall; two days later, menses occur.  The purpose of progesterone is to prepare the uterus for pregnancy.  Very little progesterone is present in the first two weeks of a menstrual cycle.  This is when estrogen levels raise, and the lining in the uterus thickens.  Progesterone makes the lining more “glandular” which will be important to carry nutrients to the fetus.  Progesterone also slows women down, increases appetite, and increases absorption of nutrients from the intestines, and stimulates breast tissue. When progesterone is swallowed ( an “unnatural” way for any hormone to be taken), studies have shown that up to 85% is converted to a sedative.  This is why women get tired, bloated, and hungry before menses.  If pregnancy occurs, the progesterone levels will be taken over by the uterus, at the end of 12 days.

Progesterone keeps the uterine lining from growing from the estrogen stimulation.  This is essential for any woman taking estrogen who has a uterus.  Unfortunately there may be side effects of weight gain, bloating, breast enlargement, headaches, and even depression.  Side effects are more pronounced in synthetic progesterone than natural.

Progesterone is a large molecule and it likes to hang out with fats.  Studies have shown that creams applied to the skin are not absorbed adequately enough to protect the uterine lining from excessive growth from estrogen use in menopause.  And they certainly should not be applied to the wrist, where they would promptly go to the breast tissue!  Vaginal application of progesterone has been shown with many studies to provide adequate protection, with a minimum of progesterone side effects.  Also there is an interesting IUD which exudes progesterone in the uterus.  This protects the patient from the systemic progesterone blues, while keeping the uterine lining thin, and eliminating the withdrawal bleeding which may occur if progesterone is being cycled.

Blood or salivary hormone levels are essentially of little use in progesterone therapy.  There are no adequate ranges for how much progesterone should be present in a menopausal female who is on progesterone therapy.  The goal with progesterone is to keep the uterine lining thin.  This can be best demonstrated with a pelvic ultrasound.  I tell my patients, that if the ultrasound looks good, the regime you are on is working.

Progesterone can be friend or foe.  Some women like the calming effects of progesterone, but many have difficulties.  With careful attention to the individual patient’s needs and responses, women can enjoy the good benefits of estrogen, while protecting the uterus.  It’s all a balance of nature.