The sex hormones (Testosterone, Estrogen and Progesterone) are made from plant substrates, such as diosgenin (Mexican yams) or stigmasterol (soybeans). These three hormones are called Bioidentical Hormones because, atom for atom, the are the same hormones that our body makes for us naturally (endogenously).
Other hormones can either be synthetically made or extracted from animals. Thyroid is a good example. Synthroid (T4), Levothroid (T4), Cytomel(T3), and Thyrolar (T3 &T4) are all synthetically produced in a lab. Armour(T3&T4) is one example of thyroid extracted from an animal; Armour comes from desiccated (dried) pig thyroids.
There has been lots of controversy regarding hormone replacement but the scientific research over the years has shown that done properly, i.e., in the hands of a trained medical practitioner, with the proper workup; physical exam, laboratory testing, follow-up etc. they are life changing for most people. There is no scientific evidence that they cause cancer (in someone who already has cancer they may not be appropriate).
Probably the easiest understood example of why hormone replacement is so important is by looking at someone with insulin-dependent Diabetes Mellitus. Insulin is of course an essential hormone that our bodies make naturally, but some people don’t make enough or even eventually don’t make hardly any at all; if they don’t get insulin injections (mainly from cows or pigs) they will become very ill and even die, if their hormone needs aren’t met
** Ron Rothenberg MD California Health