Posted by Gretchen Jones on Sep 13, 2019

I’ve been reading about the delivery of the bio-identical transdermal hormones and the dosing needed to reach therapeutic levels in the bloodstream. In my readings, I am finding that serum and urine testing are underestimating hormone delivery vs capillary testing. This has me thinking. If venipuncture serum or urine levels of the hormones delivered through the skin are not giving us an accurate picture of what is being delivered, should we be checking hormones via capillary testing?

For example, the ovaries in the pre menopausal luteal phase would produce about 10-40 mg of progesterone daily. To achieve the luteal ranges in postmenopausal women with topical progesterone therapy only requires 10-40 mg dosing when measuring saliva or capillary whole blood, but requires 10 times that amount when measuring venipuncture serum/plasma levels (100-300 mg topically).

So this then makes me ask the question. Which one of these categories of body fluids; serum, urine vs saliva, and capillary whole blood, more closely reflects tissue levels of the hormones and the optimal dose that is needed for optimal physiological response? Maybe dried blood spot levels of the topically delivered hormones more closely reflect tissue levels of estradiol and progesterone in women and testosterone in men. The data I’ve read suggests that at least for the topical estradiol and progesterone serum and urine underestimate by at least 10-fold the amount of topically delivered hormone distributed to several tissues of the body.

Breast biopsies following physiological dosing with topical estradiol (1 mg) and progesterone (25 mg) where mammary tissue levels of hormones increased 100 fold and progesterone suppressed estradiol stimulated mammary cell proliferation, but SERUM levels of estradiol and progesterone showed no significant change from patients treated only with placebo topical cream. The data is suggesting that serum and urine is not appropriate body fluids to monitor topical hormone therapy but are fine for measuring endogenous hormones, or BHRT delivered by other methods.

More research is needed to clarify these issues regarding the optimal topical hormone dose necessary to achieve clinical response to hormone replacement therapy for sure. So for those of you who are having low hormone readings without feeling like your hormones are low or out of range, I would recommend doing a blood spot test and/or saliva testing to compare. And I can’t believe I am suggesting saliva testing, but after doing some research and experiencing low serum blood levels of recent, I am open to more research and learning.

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