Hormones that are Identical – What’s the Big Deal?

A lot has been made about the importance of using hormone supplementation that is identical to human hormones, or bioidentical.  However, some doctors still lump things like synthetic, non-bioidentical ”progestins” in with progesterone when discussing the risks and benefits of hormone supplementation.  So, they must know what they are talking about, right?  What’s the big deal?  Don’t they all work pretty much the same?

Let’s take a look at this example and see if a small differences in the chemical structure of a hormone makes any difference in its activity.  To the left are the chemical structures for two hormones that every person produces in their body.  They look pretty similar, right?  In fact, the are exactly the same structurally except for a methyl group (CH3) and a hydroxy group (-OH).  So, how is their activity different?  The top one is testosterone, the primary male hormone and the bottom one is estradiol, the primary female hormone.  Big difference in activity.

Now let’s take a look at medroxyprogesterone, the synthetic progestin in Prempro, and compare it to progesterone, the human hormone.  This picture shows the structures of the two hormones.   They are obviously not identical.  So, does medroxyprogesterone have a different activity in the body than progesterone?  I can say with 100% assurance that it does.  The problem is that we don’t really know what that activity is.  In the case of medroxyprogesterone, we don’t really know what receptors they stimulate, or how they are metabolized, things we definitely know with bioidentical hormones like progesterone.

So, let’s be clear, small differences in the chemical structure of a hormone can have big differences in its activity in the body.  Given this basic understanding, it seems risky to take non-bioidentical hormones.  The results of clinical trials like the Woman’s Health Initiative confirm that assumption.  For more information about the Woman’s Health Initiative, see my blog post Brief History of Women’s Hormone Replacement.

I welcome any questions or comments.

Thank you and live well!

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