Many private clinics offering HRT often seek to boost their appeal by boasting that they provide “bio-identical HRT” or “bio-identical hormones” or “natural hormones”. These terms are synonymous, and refer to the use of hormones that are identical at a molecular level with the hormones found in the body (also called endogenous hormones). The idea of taking the “natural” hormone has an obvious appeal, both from a potential effectiveness, as well as potential safety point of view (“natural” means safe…, “natural” means effective!”). In reality, the “bio-identical” concept is largely hype and misleading.
When HRT is indicated, women are advised to take only those hormone therapies that are regulated and approved by the MHRA, which include hormones which are natural and identical to those produced in the body. There is lack of sufficient data regarding safety and efficacy of unregulated custom compounded hormones. Most commercially available and approved HRT preparations contain 17-beta oestradiol form of natural oestrogen along with progestogens - compounds which have progesterone like actions. Micronised progesterones are natural progesterones devoid of any androgenic as well as glucocorticoid activities. These appear to be the optimal progesterone in terms of cardiovascular effects, blood pressure, VTE, probably stroke and even breast cancer. Utrogestan is the only one currently available to prescribe in the UK.