Progesterone creams: Do they work?

In recent years, transdermal progesterone creams have become a popular hormone regimen for postmenopausal women, with a very large number of women being advised, or electing, to use this form of therapy as the only treatment for management of their menopause. The reason for this trend is interesting to review from a historical aspect, but is particularly disturbing when the criteria for its use, and the scientific evidence on which the regimen is based, are carefully analyzed.

The principal criterion for the success of any therapeutic intervention such as the use of transdermal progesterone cream must always be: does it work in clinical practice?

To assess this, we must carefully scrutinize the clinical evidence for and against the need and effectiveness of progesterone in management of the menopause, and particularly the use of progesterone when delivered through a transdermal cream base. The questions to be asked are:

(1) Is there any scientific evidence that transdermal progesterone prevents flushes and sweats in postmenopausal women?

(2) Does transdermal progesterone improve the elasticity and the moisture of a dry atrophic vagina?

(3) Is there any clinical evidence that transdermal progesterone stops the metabolic degradation of bone?

(4) Are there any properly conducted studies which suggest that transdermal progesterone improves moods or sexual response?

If the answer to these questions is no, then the continued prescribing of progesterone cream must be regarded as entering the realms of unethical medical practice.

The use of a progestogen in combination with an estrogen for the treatment of postmenopausal symptoms has been part of recommended medical practice for over 40 years. However, progestogens are synthetic steroids and, as such, may produce undesirable side-effects such as bloating, weight gain, androgenization and metabolic disturbances1, and more recently it has been implied that progestogens are an associated factor in the development of breast cancer among women taking combined hormone therapy2-4.

For the above reasons, there has been renewed interest in using natural (bio-identical) progesterone, to protect the endometrium and relieve menopausal symptoms, in an attempt to avoid any untoward effects associated with synthetic progestogens.

Natural progesterone, however, is very rapidly metabolized by enzymes in the gut and the liver, so use of oral progesterone is often associated with variable blood levels and, consequently, uncertain biological...