Progestogens are commonly prescribed for both peri-menopausal women to correct estrogen dominant symptoms (heavy bleeding, insomnia, weight gain, mood changes) and for menopausal women to balance their estrogen therapy. The progestogen is required for postmenopausal women on estrogen therapy with an intact uterus to prevent estrogen-induced endometrial hyperplasia and endometrial cancer. Due to the adverse effects of the most common synthetic progestogen used for menopausal therapy, many physicians and patients have turned to the natural progestogen, progesterone. Both oral and trans-vaginal administration of progesterone has been shown to be effective and well-tolerated. The lipid solubility of progesterone predisposes it toward a topical (as a cream or gel applied to the skin) method of administration. Yet this topical method has been historically questioned because serum levels do not elevate even at relatively high doses.
A study in Menopause: The Journal of the North American Menopause Society in 2013 explored progesterone levels in serum, whole blood, saliva and capillary blood when progesterone was applied topically. Although the sample size was relatively small, the authors concluded “progesterone absorption is much more efficient than has been reported solely on venous serum or plasma levels measured after topical application”. Both the salivary and capillary blood levels increase dramatically, in addition to published observations of the direct therapeutic effects of progesterone on the endometrium. The study demonstrated progesterone levels in capillary blood were 100-fold higher than those seen in serum or whole blood and10-fold higher than those in seen in saliva.
This study represents another reason that any testing (urine, saliva, or serum) is simply a guideline. The treatment plan is usually based on the symptoms and the testing only rules out overdose or imbalance. Your practitioner is usually not trying to reach specific estradiol, progesterone or testosterone levels. They are simply trying to reach a “symptom free patient”!
J. Du et al. Percutaneous progesterone delivery via cream or gel application in postmenopausal women: a randomized cross-over study of progesterone levels in serum, whole blood, saliva and capillary blood. Menopause: The Journal of The North American Menopause Society. Vol 20, No11, pp. 1169-75.