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We can test how efficient is a progesterone cream by doing saliva tests.

Over the last 14 years, many women using Natpro Progesterone Cream have done regular saliva testing. And every time they’ve come back with excellent results. Not only does the progesterone level increase substantially, but the clients feel well which the main objective is!

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Please take a look at Judy’s saliva tests’ results, a ‘before’ and ‘after’ which gives an excellent comparison. You’ll see the progesterone has increased substantially in only a month.

The progesterone level is 4000pg/ml and her estrogen 5pg/ml. making her progesterone to estrogen ratio 800:1, which is good. I’ve found it should be 600:1 and over to feel well.
===>>These tests were done using the New Natpro formula.

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Let’s clarify this issue once and for all…. Serum/plasma testing [commonly called ‘blood testing] for progesterone & Estrogen levels does NOT provide an accurate picture of our hormonal status.


The serum and saliva progesterone testing levels will not give the same results – because less than 20% of progesterone is found in serum/plasma, whereas 80% of the progesterone are attached to the red blood cell membranes.
[The plasma serum is the white watery liquid portion of the blood without the cellular component of red blood cells and white blood cells.]
Much confusion exists among medical professionals and also the general public about progesterone absorption in the body.
This confusion is based mainly on a misunderstanding of the various test used to measure progesterone levels in the body.

Let us try to clarify the issue!

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Absorption of Trans-dermal Progesterone

Progesterone is a fat loving (lipophilic) molecule. It is for that reason that transdermal progesterone cream is well absorbed through skin into the underlying fat layer. In fact, it is the most fat loving hormone among all the steroid hormones.
From the fat layer, the progesterone gradually attaches itself to red blood cell membranes in capillaries running through the fat tissue.

Only the progesterone transported by red blood cell membranes is readily available to reach all target tissues as well as the saliva.
The progesterone transported on red blood cell membrane is completely bio-available and can be readily measured by saliva testing.

Dr John Lee stated: “Only a small fraction of progesterone is carried by the watery serum. Obviously, serum testing is not a good way to measure trans-dermal progesterone absorption.
Yet, many doctors continue to question the skin absorption of progesterone. A recent example is a report in the April 25, 1998 issue of the Lancet that serum levels did not reflect a substantial rise of progesterone after topical application in postmenopausal women.

This report is being used to argue that progesterone is not well absorbed.
This implication is erroneous. Rather, it means that the authors did not understand the significant difference between serum and saliva progesterone levels. Some even imply that saliva testing is relatively unknown and its reliability is unproven. This is an odd admission since researchers have been using saliva testing for years and a number of laboratories offer routine saliva hormone testing.” Dr John Lee

What does a Conventional “Blood Test” Measure?

The “Blood” tests prescribed by most [uninformed] doctors measure the concentration of progesterone in the watery section of the blood which is called plasma or serum. Serum and plasma, being watery, contain water-soluble (hydrophilic) substances such as water-soluble vitamins, carbohydrates, and proteins. We have already clarified that Serum/plasma does NOT contain fat-soluble (lipophilic) substances.. Sex hormones such as progesterone, estrogen and testosterone are fat-soluble steroids similar to cholesterol and will be attracted to the red blood cell membranes, which is also fatty in nature.

To conclude:

  • Progesterone molecules found in the serum levels (“blood test”) are NOT readily bio-available to attach themselves to the receptors of target tissues. They are on their way to be excreted in the bile via the liver.
  • 80% of Progesterone molecules are bound to red blood cell membranes. As red blood cell membranes are fatty in nature, they will attract the fat-soluble progesterone molecules.
  • The level of bio-available progesterone ready to be used by the body can only be accurately detected by saliva testing.
  • The conventional ‘blood test’ (serum test) for progesterone will NOT detect the great majority of the progesterone present on the whole blood cell membrane.
  • Saliva testing is the gold standard to measure Progesterone levels

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Saliva testing, as opposed to blood serum testing, is the most reliable test to measure hormonal balance. However, you should be aware of some of the disadvantages and advantages of saliva hormone testing compared to blood testing.

David Zava, [Ph.D.] the founder and Chief Scientist at ZRT Laboratory, has been among the pioneer to promote the efficacy of saliva testing vs serum testing. He says:

Because of the rapid passive diffusion of steroids into the saliva, saliva testing remains the most reliable test to measure the level of bio-available progesterone in the body.

Only a small fraction of steroids in blood plasma serum are bio available.

In blood, 95-99% of the steroids are bound up by binding proteins such as sex hormone binding globulin (SHBG), cortisol binding globulin (CBG), and albumin. (3-5) The small fraction of steroids not bound is considered the free fraction, or that which is bio available as blood percolates through the capillary beds of tissues.

The free or bio available fraction of steroids in blood enters the salivary gland and the salivary duct by passive diffusion just as they enter other tissues of the body. Hence, saliva provides a convenient diagnostic fluid from which to monitor, non invasive, the bio available fraction of steroid hormones circulating in the bloodstream and entering tissues.

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 The advantages of saliva testing:

  • easy to collect and stress free.
  • Non-invasive (no needles)
  • Convenient collection and shipment by regular US mail
  • Inexpensive courier
  • Optimized for collection any time of day/month, any place
  • No special processing (E.g., centrifugation, ice-packs) prior to shipment
  • Hormones stable in saliva for prolonged period at room temperature
  • More reliable than serum for total bio available steroid hormone levels
  • Lower overall costs both for the patient, health care provider, and insurance carrier.

The disadvantages of saliva hormone testing:

  • Technically more challenging than serum testing of steroids, need 10-20 x sensitivity
  • Limited number of laboratories that can perform this test
  • Lack of technical expertise
  • Interfering substances-food, beverages
  • Saliva easily contaminated with topical hormones on lips or hands
  • Spurious results with periodontal disease (more problem with chewing gum)
  • Wrongly believing that serum is gold standard
  • Sub-lingual use of hormones often leads to inaccurate (high) results
  • No proficiency testing (CAP, AAB) that reflects saliva hormone levels
  • Topical application of hormones results in saliva levels higher than serum

The ideal saliva hormone test report should contain patient information not only about an individual’s hormone level but how this relates to symptoms associated with hormonal imbalance. These other relevant information are essential to provide an ideal saliva hormone test report:

  • Gender, Age,
  • Menopausal status,
  • Menstrual cycle information,
  • If woman had her ovaries removed
  • Usage of hormones (types, delivery systems such as oral vs. topical, dosage) and when last used will impact the test results and ranges
  • Which phase of the menstrual cycle (follicular vs. luteal) as progesterone level will differ
  • The delivery systems when taking replacement therapy (oral vs. topical).

Those differences should be mentioned in the test result. Otherwise, the results can be misleading. For instance, a postmenopausal woman using progesterone cream will have a higher salivary progesterone levels than a post menopausal woman who is not supplementing.

The RATIO of Progesterone to Estrogen is more Critical than the LEVELS

To Conclude:

Saliva hormone testing is more convenient than serum hormone testing. It is less stressful, more cost-effective, and more representative of the bio-available progesterone or estrogen in blood. The ratio of progesterone to estrogen is easily done with saliva hormone testing.

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