Kentucky Program for Bioethics and Patients' Rights, has stated that she believes BHT is an experimental therapy that is often prescribed by practitioners who sell the products, and are thus in an unethical position of conflict of interest. Rosenthal has also described problematic issues with BHT including patients receiving information from popular books while lacking the scientific literacy to separate rhetoric from evidence about hormone replacement, illegitimate claims of a "big pharma" conspiracy to suppress bioidentical prescribing, the extra and unnecessary cost of the products that are often not covered by insurance plans, and the inaccurate depiction of bioidentical prescribing as "cutting edge science" rather than unproven alternative medicine. "Natural" claims Bioidentical hormones are frequently marketed as being "natural", or more natural than conventional HRT. The term natural can be used to suggest or emphasize a variety of different ideas—similarity with endogenous hormones, extraction from a plant-based source, and that the hormones are not manufactured or synthesized. Endogeny: this meaning of natural implies that the hormones are molecularly identical to those found within the body. However, BHT is unnatural as it opposes the biologically determined declining levels of fertility hormones in aging women and medicalizes a stage of human life that is probably normal. Most of the conjugated equine estrogens extracted from pregnant horse urine (such as Premarin) are converted to human estrogens once they enter the body. However, not all are converted, and BHT advocates allege that the small amount that is not converted may have some harmful effects. This is still being studied. Plant-derived: Women who purchase compounded BHT are more likely to associate natural with the idea that the hormones are derived from plant sources. However, both bioidentical and non-bioidentical hormones are sourced from the same plants, generally soy beans or yams. Manufacturing: both bioidentical and non-bioidentical hormones are synthesized using the same chemical precursors; diosgenin is extracted from soy or yam plants, converted into progesterone and used as a hormone chemical precursor to create the final product. "Natural" is also used to promote the idea of being unmodified, and containing the "goodness" of a pure substance. However, this argument simultaneously draws upon a scientific discourse and methodology; even hormones called "bioidentical" have been heavily processed and converted in a pharmaceutical lab. Premarin (conjugated estrogens extracted from the urine of pregnant horses) contains the only truly "natural" hormones—natural in the sense of being completely unmodified beyond blending