Bioidentical Hormone Replacement

Where the term came from

A 2011 literature review searched databases and the internet to June 2010 and found 63 different definitions of bioidentical hormones. It proposed a concise definition: chemical substances that are identical in molecular structure to human hormones. A 2007 commentary in the Journal of General Internal Medicine characterized the term bioidentical as a pseudoscientific neologism referring to hormones such as estradiol, estriol, estrone, progesterone and testosterone, and noted that these hormones are synthesized or semisynthesized from plant sterols in the laboratory.

The Endocrine Society's position statement adds that any hormone can be made bioidentical and that many FDA-approved hormone preparations are bioidentical, while the term has also come to describe compounded formulations containing estrogens, progesterone and androgens.

Interest after the Women's Health Initiative

The Endocrine Society states that the 2002 Women's Health Initiative trial of oral conjugated equine estrogens with medroxyprogesterone acetate raised safety concerns, that many clinicians and women then stopped hormone therapy, and that this created an environment in which the idea that compounded bioidentical therapy might be safer and more effective spread without testing. A 2024 review in Frontiers in Reproductive Health likewise traces the growth of compounded products to that 2002 publication and reports that US prescriptions for menopausal hormone therapy fell by 84 percent between 2002 and 2020. A 2007 commentary also observed that interest in bioidentical hormones appeared to have increased since 2002.

Popular books and promotion

The 2011 definitions review links the popularity of bioidentical hormones in part to popular press coverage, naming the 2006 book Ageless: The Naked Truth About Bioidentical Hormones by the actress Suzanne Somers. The 2007 commentary reports that Somers published three books promoting the approach in three years, and describes an earlier popular literature on progesterone cream that attributed many conditions to estrogen dominance. The 2024 review characterizes the claims in the Somers book as lacking a credible scientific rationale and reports that popular books on the topic often rely on unreliable sources. The sources reviewed for this page do not describe the work of T. S. Wiley, so it is not assessed here.

Bioidentical as a chemical description

In its chemical sense, bioidentical describes a molecule with the same structure as a hormone the human body produces. The Endocrine Society states that there are many FDA-approved hormone preparations that are bioidentical. A National Academies report prepared at the request of the FDA explains that it uses the word only as an identifier to communicate its conclusions, states that this is not an endorsement, and notes that the public often misunderstands the term. The report also notes that patients may wrongly believe bioidentical hormones are available only from compounding pharmacies.

Licensed versus compounded preparations

Sources separate two groups. Licensed bioidentical products, such as estradiol and micronized progesterone, have been reviewed by a regulator for safety and efficacy. Compounded bioidentical hormone therapy, abbreviated cBHT in several sources, refers to preparations made by a pharmacy for an individual prescription, often marketed as natural or bioidentical. The American College of Obstetricians and Gynecologists states that many compounding pharmacies use the phrase bioidentical hormone as a marketing term implying that preparations are natural and therefore safer and more effective, and that evidence for such claims is lacking.

Related Machipedia pages

This page belongs to the Machipedia family page Hormone Replacement Therapy, which lists the compounded form as Compounded bioidentical hormone therapy, and the licensed products are covered on Menopausal Estrogen-Progestogen Therapy. Compounded hormone pellets are covered by name on Hormone Pellet Therapy, and compounded or licensed testosterone for women on Testosterone Therapy in Women. The NICE menopause guideline uses a different phrase, unregulated hormone preparations, for products outside licensing systems.

Licensed products with identical hormones

The Endocrine Society lists FDA-approved preparations with structures identical to endogenous hormones: oral estradiol, estradiol patches, gels, sprays and lotions, vaginal estradiol creams, tablets, rings and inserts, and micronized oral or vaginal progesterone. It states that these are made under strict manufacturing oversight, dispensed by retail pharmacies, and had efficacy for menopausal symptoms established in 12-week placebo-controlled trials before approval.

Custom-compounded preparations

A compounding pharmacy prepares a medication to a prescriber's order, for example combining hormones in one preparation or making a different dosage form. The 2007 commentary describes compounded menopausal products that include estriol and mixtures of estrogens, and states that compounded products are not subject to the manufacturing standards that apply to licensed drugs. The Endocrine Society notes that compounded formulations may combine different forms of estrogen or progesterone with different potencies and may be offered at lower cost than licensed products, which can motivate requests.

Hormone testing and individualization

Individualization is a defining feature in promotion. The 2007 commentary reports that saliva testing for hormones has been promoted to individualize dosing. In a qualitative study of 21 US women who used or had used compounded bioidentical therapy, participants described a sense of biological tailoring, both through a chemical match to endogenous hormones and through dosing based on blood or saliva tests or on symptom profiles, and held varied views on the value of such tests. In two US surveys, 21 percent of one subset of women using hormone therapy said theirs had been personalized based on hormone levels.

Who delivers it

In the two US surveys analyzed by Pinkerton and Santoro, most women using hormone therapy stated that their physician had recommended the treatment, and the authors estimated that between 1 million and 2.5 million US women aged 40 or older use compounded hormone therapy. Participants in the qualitative study also described consulting naturopathic physicians who were familiar with compounded therapy. See Naturopathy for the profession. Pellet forms are discussed on Hormone Pellet Therapy.

Menopausal symptoms and fear of conventional therapy

Compounded bioidentical therapy is mainly promoted for menopausal symptoms. In interviews with 21 women, two groups of motivations emerged: push motivations, including fear about the safety of conventional hormone therapy, an aversion to conjugated estrogens, and distrust of a medical system perceived as dismissive; and pull motivations toward compounded products. The Endocrine Society states that compounded products have been promoted as safer and more effective alternatives to manufactured licensed therapy for menopausal symptom relief.

Disease prevention and anti-aging claims

The 2007 commentary reports that compounding pharmacy materials claimed protection against heart disease, breast cancer and endometrial cancer, and that progesterone creams were promoted as general health tonics, without clinical trials supporting those claims. A 2024 review reports that a convenience sample of 100 websites promoting compounded bioidentical therapy in 2017 made claims of lower risk than licensed products, anti-aging effects, improved libido, reduced breast cancer risk, weight loss and enhanced fertility, and that a 2024 check of websites found no change. It reports that these claims were not supported by the scientific literature.

Evidence reviews and position statements

The National Academies report of 2020 concluded that there is insufficient evidence to support the overall clinical utility of compounded bioidentical hormone therapy for menopause and male hypogonadism symptoms. It found insufficient data to show that compounded therapy is as safe as, or safer than, licensed therapy, and insufficient data to show it is as effective.

The Endocrine Society states that no comprehensive trial has examined the safety or efficacy of compounded bioidentical therapy for symptom relief and that no clinical outcomes trials have been completed. ACOG's 2023 clinical consensus, reaffirmed in 2026, states that compounded bioidentical menopausal hormone therapy should not be prescribed routinely when FDA-approved formulations exist and calls for placebo-controlled randomized trials with long-term follow-up. The NICE guideline recommends explaining that the efficacy and safety of unregulated hormone preparations are unknown.

Evidence for licensed hormone therapy

The abstract of the 2022 Menopause Society position statement states that hormone therapy remains the most effective treatment for vasomotor symptoms and the genitourinary syndrome of menopause, that risks differ by type, dose, duration, route, timing of initiation and whether a progestogen is used, and that benefit-risk balance depends on age and time since menopause. The abstract does not discuss compounded products. A 2024 review states that claims for compounded therapy are often borrowed from trials of licensed products.

Saliva and blood hormone testing

The 2007 commentary states that correlations between serum and salivary levels of reproductive hormones vary by hormone, time of day, diet and type of assay, that salivary progesterone levels are unreliable, and that hormone levels do not correlate with menopausal symptoms. It adds that salivary tests may encourage hormone use or higher doses than symptoms require. A 2017 qualitative study summarizes the literature as rejecting both saliva and blood testing as inconsistent and ineffective for determining dose.

Absorption and product variability

A 2024 review reports an analysis of creams and capsules from 13 compounding pharmacies that found estradiol and progesterone content ranging from 73 percent to 135 percent of the labeled amount, with inconsistencies within the same pharmacy. It also describes a descriptive study of compounded estradiol pellets in 114 women in which serum estradiol levels varied widely between participants and one implant produced supraphysiologic levels for over a year in some cases. These are second-hand summaries of observational studies.

Endometrial safety data

The 2007 commentary reviewed three studies of whether topical progesterone cream can oppose estrogen's stimulation of the uterine lining. The longest, 48 weeks, found that the cream could not effectively oppose estradiol-induced stimulation,, while a 28-day study reporting an effect was judged too short to assess estrogenic effects. These findings concern specific preparations.

Reported harms

The 2007 commentary states that natural hormones, including estradiol, estriol, estrone and progesterone, can be expected to have the same adverse event profile as conventional menopausal hormone regimens, and a 2024 review states that a medical contraindication to licensed hormone therapy would also apply to compounded therapy. The Endocrine Society reports that adverse events, including endometrial cancer, have been observed in a survey of women taking compounded therapy and that a study found blood levels well above the expected range in women using compounded pellets.

A 2024 review summarizes a retrospective cohort of 384 women using compounded estradiol pellets and 155 using licensed therapy, followed for a mean of 3.5 years, in which bothersome side effects or adverse events were reported by 57.6 percent of pellet users and 14.8 percent of licensed-product users. The study was not randomized. The same review reports that impurities and lack of sterility have been observed in compounded products given by injection.

Endometrial hyperplasia and progestogen protection

Women with a uterus who take estrogen are usually given a progestogen to oppose estrogen-induced endometrial hyperplasia and cancer. A 2017 study reports that the literature raises concern that inconsistencies in the quality of compounded products could result in inadequate progestogen to protect the endometrium, and that the use of testing to set dosage may lead to more estrogen than needed for symptom control. The sources reviewed do not give a frequency for this outcome.

Professional-body oversight statements

The Endocrine Society states there is no evidence-based medical need for compounded hormone therapy when a licensed preparation is available, and supports oversight of purity, dose accuracy and adverse-event reporting for all hormones. The National Academies report concluded that patient preference alone should not determine use, and described possible exceptions such as allergy to an ingredient in a licensed product or a need for a dosage form not otherwise available. ACOG advises clinicians to counsel patients about the lack of approval and the risks specific to compounding. A national survey analysis found 86 percent of women in one survey were unaware that compounded products are not FDA-approved.

Care boundaries

This page is information only and does not recommend or advise against any treatment. Menopausal symptoms, uterine bleeding, breast changes and the decision to start, change or stop hormones should be discussed with a qualified clinician, and necessary care should not be delayed or replaced. The sources reviewed do not cover other uses promoted for compounded hormones, such as thyroid or adrenal preparations.