Bioidentical hormones: the distinction that actually matters

Two things, one word

Regulated body-identical hormone therapy contains estradiol identical to human estradiol, and micronised progesterone identical to human progesterone. These are licensed medicines, made to pharmaceutical standards with consistent dose, and they are what a great deal of modern hormone therapy already consists of.

Compounded bioidentical hormone therapy is mixed by a compounding pharmacy to an individual prescription, often as a cream or troche, frequently containing several hormones, and often prescribed on the basis of saliva or blood hormone testing.

Marketing routinely uses the same word for both, which lets the regulatory status of the first attach itself to the second.

What professional bodies say

The position is consistent across major menopause and endocrine societies, and it is unusually firm for this field.

Regulated body-identical preparations are supported and widely recommended. Micronised progesterone in particular is often preferred over older synthetic progestogens on the basis of its breast and cardiovascular profile in observational data.

Custom-compounded preparations are not recommended. The reasons given are that they are not subject to the testing required of licensed medicines, that dose consistency between batches has been shown to vary, that they generally carry no product information or safety labelling, and that there is no evidence they are safer or more effective than licensed alternatives despite that being the central marketing claim.

The endometrial safety issue

This is the most concrete concern rather than a regulatory one. Estrogen given to a woman with a uterus requires adequate progestogen to protect the womb lining, which otherwise thickens and can progress to hyperplasia and endometrial cancer.

Licensed regimens have established the dose and duration of progestogen needed. Compounded preparations, particularly progesterone creams, may not deliver enough absorbed progesterone to provide that protection, and cases of endometrial hyperplasia associated with their use have been reported.

Anyone with a uterus using a compounded preparation should specifically establish whether their endometrial protection is adequate and evidenced.

Why saliva and blood testing is a red flag

Compounded prescribing is frequently justified by hormone testing and dose adjustment to a target level. Professional bodies do not support this approach.

Salivary hormone levels do not correlate reliably with tissue levels or with symptoms. Serum levels fluctuate substantially and are not the basis on which hormone therapy is titrated in standard practice, where dose is guided by symptom response.

A prescriber who bases an individualised compounded formula on a saliva panel is using a method with no supporting evidence for that purpose.

When to see someone

If you want body-identical hormones, that is a reasonable and mainstream request that can be met with licensed, regulated products. Asking for estradiol and micronised progesterone by name is a clear way to have that conversation.

If you are currently using a compounded preparation, raise endometrial protection specifically if you have a uterus, and ask what evidence supports the formulation. Do not stop abruptly without advice.