Non-FDA approved “bioidentical” hormones are not regulated and have not been subjected to scientific studies assessing their quality and safety. As the manufacturing process of these drugs isn’t regulated there is no guarantee of consistent dosing between batches. Furthermore, we have no evidence as to their efficacy, particularly in women with POI, and so their use can’t be recommended at present.
There are options for prescribing bio- or body-identical HRT products on the NHS which have been approved by the licensing authorities. Essentially by this we mean estradiol (rather than the conjugated estrogens made from pregnant mares’ urine) and progesterone (rather than synthetic progestogens). These are the same molecules which the body produces naturally (ie “body-identical”) and so they tend to have fewer side effects. Unlike the unlicensed, compounded bioidentical hormones, these drugs are regulated and have been studied in many clinical trials.