Caution on the use of saliva measurements to monitor absorption of progesterone from transdermal creams in postmenopausal women.
Level 2 - randomized trial
Double-blind placebo-controlled randomized trial
PubMed 11809337 · doi:10.1016/s0378-5122(01)00250-x
What was done
A double-blind, placebo-controlled trial evaluated 24 postmenopausal women randomized to apply transdermal creams (placebo, 20 mg/g, or 40 mg/g progesterone) twice daily. The regimen consisted of two 3-week application periods separated by a 1-week washout. Morning samples were collected at weeks 0, 1, 3, 4, 7, and 8 to measure progesterone concentrations in plasma, red blood cells, and saliva, alongside urinary pregnanediol-3-glucuronide excretion.
What was found
The abstract reports no numerical values. Compared to placebo, progesterone cream produced only small increases in plasma progesterone concentrations and urinary pregnanediol-3-glucuronide excretion. Red blood cell progesterone concentrations never exceeded plasma levels. Conversely, saliva progesterone concentrations were very high and highly variable in active treatment groups, presenting a paradox relative to expected plasma-to-saliva ratios.
Why it matters
This study demonstrates that systemic absorption of progesterone from transdermal creams is poor and cautions clinicians against relying on salivary hormone panels, which can misleadingly suggest high tissue exposure despite low circulating levels.
Limits
The study sample was small (n = 24 split across three arms), and the abstract provides purely qualitative descriptions without reporting means, variances, or p-values. Clinical endpoints such as endometrial protection were not evaluated.
Cited by
- context Topical hormone creams can accumulate in adipose tissue, resulting in erratic or aberrant release into the bloodstream.