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Some hormone medications have exactly the same chemical structure as the hormones produced naturally in your body.  These are described as being  “body-identical”.


The female body naturally creates the sex hormones oestrogen, progesterone and testosterone, which interact within a sophisticated, complex system. 

When oestrogen started to be used for symptoms of menopause, it was derived  from pregnant horse urine! (Female mammals make a lot of oestrogen when pregnant and very little when breastfeeding). Premarin is the name of this oestrogen formulation and it has been used for many decades. There is a lot of research published on Premarin as a result of this. Scientific advances then allowed the manufacture of non-body-identical hormones that act like the body’s natural hormones and more recently, body-identical hormones – those just the same as your own body makes.

Your female body naturally makes the following sex hormones-


There are 3 types of oestrogen your body makes-

  • oestradiol is produced in the ovaries and the predominant form of oestrogen during the menstruating years;
  • oestriol is produced in very high levels by the placenta during pregnancy; 
  • oestrone is produced by the ovaries, adrenal glands and fat tissue in postmenopausal females.

Many tissues also have the ability to form active oestrogen for their own needs as oestrogen receptors are contained in most cells and tissues of the body. This process continues after menopause when your ovaries have stopped working so hard, so you always have some natural production, even if you have had your ovaries removed.

Body-identical oestrogen can be taken as a tablet, applied through the skin in a patch or gel or used directly in the vagina.


Progesterone is a key hormone that acts as a counterbalance in a sophisticated relationship with oestrogen. It is produced by the ovaries in the second half of the menstrual cycle. Small amounts are produced after menopause in both the ovaries and adrenal glands. Even though we think of oestrogen as the main female hormone, your body actually has much more progesterone.

Body-identical progesterone is available as a capsule.


You may be surprised to learn that females have more testosterone than any of the other sex hormones. Testosterone is produced in the ovaries and adrenal glands but at a level less than one hundredth that of males. (Males also have oestrogen and progesterone BTW). 

Body-identical testosterone is a cream applied to the skin. Read more about testosterone.



We can obtain body-identical hormones treatment from two major sources: those available through a prescription and those created through a process called compounding. 

The term “bio-identical “ is often used to describe compounded body-identical hormones. Compounded preparations are less regulated than prescription and generally more expensive. 

Compounded drugs are created by a pharmacist from base ingredients and mixed in a tailored way. The formulations available through a prescription are subject to strict regulation under the Therapeutic Goods Act (TGA), meaning there have been rigorous clinical trials for the quality, safety and manufacturing processes. Body-identical hormones that come through the alternative route of compounding sit outside this regulatory framework and are not guaranteed to be as pure and the dose cannot be guaranteed. This potentially reduces their reliability, safety and increases their cost. Ultimately, the chemical structure of such hormones is the same, however the dose and purity may differ. The Australasian Menopause Society does not recommend the use of compounded body-identical hormones for these safety reasons and there is even less reason to use them now there are prescription body-identical hormones available in Australia. 


It is important to note that the majority of studies on both the benefits and risks of hormone replacement therapy are done using non-body-identical hormones. Any conclusions made from these studies should take that into consideration and it is very likely that body-identical hormones will be even safer.

Zoely and Qlaira are the only oral contraceptive pills that contain body-identical oestrogen. None contain body-identical progesterone.
This information is for general educational purposes only and does not constitute medical advice. Please see your health professional for advice that is personalised to you.
Key Take Aways

Body-identical hormones are the same as your body makes

Only prescription hormones are fully regulated


Other resources

Australian Menopause Society on bio-identical hormones

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