NEAL ROUZIER, M.D.
Has there been any progress on new reference ranges on progesterone? My patients are coming back with levels of 2-5 ng/mL which was confusing to me until I read on the forum about the reagent. I’d appreciate any update.
Based on looking at many recent tests, I think the new range should be at least >2. Still working on that with LabCorp. Again it is completely arbitrary and nebulous. Unfortunately the manufacturer of the new reagent, nor LabCorp Executives, have recommended a certain level of normal or optimal to shoot for. Just goes to show how these numbers are picked and how they should be used as only a guide.
The consensus meeting of OB/GYNS in Europe last year felt that a level of 10 ng/dl was adequate for endometrial protection. Unfortunately that number was established using the old reagent but has now been discontinued. Ultimately the number that will be decided on will be based on negotiations between me and a few pathologists at LabCorp. Now how scientific is that? Hard to believe that LabCorp would suddenly start using a new reagent without reference ranges and without alerting the public as to their doing so.
Use the number as a guide but keep an eye on bleeding or spotting. Based on doing this for 20 years, I still feel that the doses we prescribe (100mg SL or 200mg PO) should be adequate for most women. The OB/GYN community does not follow levels like I do, so a lot of their dosing is based on the studies that show 200mg PO is protective, which in our experience results in P4 levels of at least > 10ng/dl. In my experience, about 20% will require more progesterone to prevent endometrial proliferation. Use your clinical judgement as well as inform the patient to be alert for any abnormal bleeding/spotting which would then require an endometrial ultrasound/biopsy and dosage increase of progesterone. So we never will truly know the exact or best level to shoot for, however with time and experience we will eventually come to know what level to shoot for in most women, with a few outliers requiring more. Remember all women are like snowflakes, all are different and will respond differently depending on cellular sensitivity to progesterone and intestinal absorption.
We hope this preliminary information is helpful, please comment as we all work collectively to resolve this issue. Thanks to many of you for reaching out with your initial concerns, it has helped us to better figure out what is happening as we reach out to LabCorp to re-establish some starting guidelines. As soon as we have more definitive information Dana will send along an update.