Is there an estrogen in conjugated estrogens (CE) that is biologically identical to an estrogen produced by the human body?

From the Guidelines

Yes, conjugated estrogens (CE) contain estrone sulfate, which is biologically identical to estrone, an estrogen naturally produced by the human body. Estrone is one of the three main estrogens found in humans, along with estradiol and estriol. In the body, estrone sulfate serves as a circulating reservoir that can be converted to active estrone. However, it's essential to note that CE products (such as Premarin) are primarily derived from pregnant mare's urine and contain multiple estrogen compounds, many of which are not found in humans. These include equilin and equilenin, which are unique to horses. This is why CE is not considered a bioidentical hormone therapy overall, despite containing one component (estrone) that matches human estrogen. When seeking hormone therapy that more closely mimics human hormones, some patients and providers prefer 17-beta estradiol preparations, which contain the predominant and most potent estrogen naturally produced by human ovaries 1.

Some key points to consider:

• The quality of evidence on the benefits and harms of hormone replacement therapy (HRT) varies for different hormone regimens 1.
• The USPSTF recommends against the use of menopausal hormone therapy for the primary or secondary prevention of cardiovascular disease 1.
• Other expert groups have recommended that women who decide to take HRT for the relief of menopausal symptoms use the lowest effective dose for the shortest possible time 1.
• The safety and effectiveness of bioidentical hormone therapy have not been evaluated through the FDA's drug approval process 1.

In terms of the most recent and highest quality study, the 2013 USPSTF recommendation statement 1 provides the most relevant guidance on the use of hormone therapy in postmenopausal women. This statement notes that the estimates of the absolute risks and benefits of hormone therapy are derived primarily from the Women's Health Initiative (WHI) study, which used oral conjugated equine estrogen and medroxyprogesterone acetate. However, it's essential to consider individual risk factors and preferences when selecting effective interventions for reducing the risks for fracture, heart disease, and cancer. Clinicians should develop a shared decision-making approach to preventing chronic diseases in perimenopausal and postmenopausal women, taking into account the latest evidence and guidelines 1.

From the FDA Drug Label

The primary source of estrogen in normally cycling adult women is the ovarian follicle, which secretes 70 to 500 mcg of estradiol daily, depending on the phase of the menstrual cycle. Estradiol is the principal intracellular human estrogen and is substantially more potent than its metabolites, estrone and estriol at the receptor level

There is 1 estrogen in conjugated estrogens that is biologically identical to an estrogen produced by the human body: Estradiol is not the only estrogen present in conjugated estrogens, however, Estrone, which is one of the estrogens present in conjugated estrogens, is biologically identical to an estrogen produced by the human body, but the most potent and principal intracellular human estrogen is Estradiol.

• The FDA label does mention that Estrone is one of the estrogens produced by the human body, but it is not the most potent one.
• Estradiol is the principal intracellular human estrogen, but the question is about conjugated estrogens, and the label does not explicitly state that Estradiol is one of the estrogens present in conjugated estrogens.
• However, the label does mention that conjugated estrogens are used in a study, and Estrone is one of the estrogens produced by the human body, and it is present in conjugated estrogens. The FDA drug label does not answer the question.

From the Research

Estrogen in Conjugated Estrogens

• There is evidence to suggest that one of the estrogens in conjugated estrogens is biologically identical to an estrogen produced by the human body 2.
• Conjugated estrogens consist of different metabolites, including estrone sulfate, which can be activated into estrone and 17 beta-estradiol in a tissue-specific manner 2.
• 17 beta-estradiol is a biologically identical estrogen to the one produced by the human body and is also used as a replacement therapy in its own right 3, 4.
• The use of conjugated estrogens, which include 17 beta-estradiol as one of their metabolites, has been shown to be effective in reducing menopausal symptoms and preventing bone loss 3, 4.

Comparison with Other Estrogens

• Conjugated equine estrogen (CEE) and 17beta-estradiol have been compared in clinical trials, with both showing consistent and comparable effects on the treatment of menopausal hot flashes 4.
• The study found that both CEE and 17beta-estradiol significantly reduced the weekly number of hot flashes compared to placebo, with no significant difference between the two agents 4.
• The use of conjugated estrogens, including CEE, has been shown to be effective in reducing menopausal symptoms, although the choice of estrogen and progestogen should be individualized based on patient preferences and medical history 3, 5.