Types of Steroids



The word ‘steroid’ is derived from Greek, where the prefix ‘ster’ is derived from the word ‘STERE’ which means a solid, and the suffix ‘oid’ is derived from the word ‘EIDOS’ and is commonly affixed in Greek as a suffix as ‘OIEDES’, which means a three dimensional form or shape. The end result in Greek is STEREOIEDES, simplified in modern English as the word steroids, or steroid.

Steroids are organic compounds that hold a chemical structure characterized by a particular arrangement of four cycloalkane rings that are connected to one another. These rings are composed of at least twenty carbon atoms that are bound together, which form the ring shapes. These rings are labeled as A, B, C and D rings. The A, B, and C rings are cycloalkane rings known specifically as cyclohexane rings (rings that contain 6 carbon atoms). The D ring differs from the other rings due to the fact that it is known as a cyclopentane ring (a ring that contains 5 carbon atoms). Different steroid compounds differ based on varying structural differences centered on the primary four ring steroid structure, which may involve variations in the functional groups attached to the central four rings, or other smaller modifications (such as the change in a single hydrogen, carbon, or oxygen atom).

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There are many different types of steroids, the majority of which do not have anything what so ever to do with muscle growth, strength, or athletic performance. Many steroids, in fact, destroy and break down muscle tissue (these are known as corticosteroids). There exist hundreds of different types of steroids and steroidal compounds in nature, and they exist in plants, animals, insects, and even fungi. Naturally occurring steroids are synthesized in cells of the different aforementioned organisms. There exist many different types of steroids in the human body, such as: Cholesterol, Cholecalciferol (Vitamin D), Estrogen, Testosterone, and Cortisol (among many others). Vitamin D in particular is what is known as a secosteroid, which is a steroidal molecule but contains a broken ring. In the human body, Cholesterol is the precursor to the development of all other steroids manufactured in the human body. This is to say that Cholesterol is the base steroidal compound that the body’s cells use to synthesize all other steroids (Estrogen, Testosterone, Vitamin D, etc.).

The types of steroids that we are concerned with in particular are known as anabolic steroids. These are also properly referred to also as anabolic androgenic steroids (often abbreviated as AAS). The word ‘anabolic’ refers to the process of tissue-building or tissue synthesis (in this case, muscle tissue) and is derived from the Greek words ‘ana’ which means “upward” and ‘ballein’ which means “to throw”. The word ‘androgenic’ refers to the masculinizing effects, and is derived from the Greek words ‘andro’ which means “male” or “masculine” and ‘genes’ which means “to produce”. The word ‘steroid’ refers to the steroid nature of the compound, as explained recently above. This is to mean that anabolic steroids are steroids that promote tissue building or tissue growth, and in this case it refers specifically to muscle tissue anabolism. Androgenic steroids refer to steroids that generate masculine features. There exist no anabolic steroids where the androgenic and anabolic effects are entirely separate from one another (they are intrinsically intertwined) and thus anabolic steroids are referred to in full as androgenic anabolic steroids (or anabolic androgenic steroids).

The number one primary anabolic steroid manufactured in every human body and in most animal species is the hormone Testosterone. It is the male sex hormone that provides the male gender with the commonly known male traits (deepening of the voice, development of bodily and facial hair, and increases in muscle size and strength). Testosterone is responsible for governing the maintenance and control of many different functions in the human body, and muscle growth is but only one of many of these functions it is responsible for governing. There exist two other naturally endogenously produced anabolic steroids in humans: Dihydrotestosterone (DHT) and Nandrolone. These are the three naturally manufactured anabolic steroids by which all other anabolic steroids are derived from and based upon.

There exist hundreds of different anabolic steroids that have been synthesized and created, all of which are based on and derived from one of the three aforementioned anabolic steroid hormones (Testosterone, Dihydrotestosterone, and Nandrolone). This is to say that all anabolic steroids in existence are modified forms of Testosterone, Dihydrotestosterone, or Nandrolone. These modified variants of these hormones are what are known as anabolic steroid analogues or derivatives. That is to say that if an anabolic steroid is an analogue or derivative of Testosterone, it is simply Testosterone with a modification to its molecular chemical structure. The following is an example of the difference between the structure of Testosterone and the structure of a known analogue of Testosterone, Methandrostenolone (Dianabol):

This essentially categorizes all anabolic steroids as one of the following types of steroids:

1. Testosterone analogues (or Testosterone derivatives)

2. Dihydrotestosterone analogues (or Dihydrotestosterone derivatives)

3. Nandrolone analogues (or Nandrolone derivatives)


These are the three types of steroids. These three anabolic steroids could be referred to as ‘progenitor hormones’ or ‘parent hormones’, as they are what the various anabolic steroids are derived from. Technically, Testosterone is quite literally the original and primary anabolic steroid by which every single anabolic steroid is derived from. Within the human body, Testosterone is the precursor hormone to Dihydrotestosterone and Nandrolone. Without Testosterone, these two other anabolic steroids would not even exist within the human body. Testosterone is metabolized into Dihydrotestosterone in the body by way of the 5-alpha reductase (5AR) enzyme (meaning Dihydrotestosterone is a metabolite of Testosterone), and furthermore, Nandrolone is a byproduct of the aromatization (conversion) of Testosterone into Estrogen[i]. Without Testosterone, Nandrolone and DHT would not even exist, which further explains that without the existence of DHT and Nandrolone, none of their analogues and derivatives would exist.

Furthermore, the development of an anabolic steroid derivative will often frequently take on the same properties and characteristics of its parent hormone (or progenitor hormone). For example, a characteristic of Dihydrotestosterone (DHT) is its inability to convert into Estrogen because it is unable to interact with the aromatase enzyme. As a result, DHT derivatives all share this same characteristic trait, passed down from the parent/progenitor hormone DHT. One additional important point to understand under the concept of analogues and their progenitor hormones is the following: upon modifying the chemical structure of a progenitor hormone to create a different anabolic steroid with different properties and attributes, the result is a compound that is, by many accounts, supposed to exhibit properties that are shared with its progenitor hormone (as evidenced by the example outlined above in regards to DHT derivatives). However, that is in theory. In practice what may occur is the opposite, or a differing effect. This is because it must be understood that once an anabolic steroid is modified (DHT, for example) to create a brand new type of steroid analogue, the resulting analogue is actually considered now a totally different hormone with unique properties and it may or may not share characteristics with its parent/progenitor hormone. But we still properly refer to them, for example, as DHT or DHT derivatives (or Testosterone derivatives, Nandrolone derivatives, and so on and so forth).

Testosterone is the number one naturally endogenously manufactured anabolic steroid by the human body, and it is the root anabolic steroid for the synthesis of all other anabolic steroids in existence.

The Concept and Purpose Behind Modifying Testosterone to Create Analogues

The concept behind chemically altering and modifying Testosterone is to create variants and analogues of Testosterone that could exhibit varying effects in the body that may be more beneficial in certain areas of function than Testosterone originally would be. Such modifications would allow a particular anabolic steroid analogue to be more preferable to treat a certain condition or disease in medicine than Testosterone itself would be able to. Other reasons for the modification of Testosterone resulting in different anabolic steroid derivatives include the development of a more convenient anabolic steroid for various individuals in different age groups (children or elderly patients, for example), gender categories, or for patients suffering from debilitations and diseases whereby Testosterone itself may worsen an individual’s medical condition in a certain area (in such a case, an analogue that may avoid effects in a particular area of the body may be beneficial).

One particularly specific goal behind the creation of different types of steroids is the quest to create what would be considered a perfect anabolic steroid. This is evidenced by the anabolic steroid development boom of the 1950s – 1980s. The quest during this anabolic steroid boom was to develop/discover an anabolic steroid that could be considered ‘perfect’ in the sense that it would provide the user with all of the benefits of the anabolic effects, and none of the undesirable estrogenic or androgenic side effects. Although no anabolic steroids have ever been deemed as the ‘perfect’ and 100% safe anabolic steroid, there are a few anabolic steroids that have come the closest to this idea of the perfect steroid.

When the concept of anabolic steroids for the purpose of performance and physique enhancement is considered, the idea behind the use of different anabolic steroid types is quite clear. The first obvious idea behind the development and use of different analogues is that of the use or discovery of an anabolic steroid analogue that would exhibit a stronger anabolic effect than Testosterone itself. If a stronger anabolic effect with a reduced strength in androgenic effects is created, an anabolic steroid that exhibits less undesirable side effects and more of the desirable anabolic effects would be favorable to an athlete. This is also the concept behind the use of an anabolic steroid that would provide the athlete with less negative effects while exhibiting more of the positive effects. In creating different types of steroids and analogues, different anabolic steroids can exhibit different attributes that are favorable to the athlete in comparison to Testosterone itself, which may present some disadvantages for athletes in various areas. This is especially true for athletes involved in various sporting activities in which the use of Testosterone or various other anabolic steroids are unfavorable due to various attributes they may have that could possibly reduce performance in specific athletic activities.

For example, anabolic steroids such as Testosterone have a tendency to promote water retention through their ability to be aromatized into Estrogen via the aromatase enzyme. While such an effect might not be a concern for a strength athlete or a powerlifter (such an effect might even be beneficial or desired in such sports), this is not a desired effect for athletes involved in sports that involve speed and swiftness, such as sprinting. Instead, a sprinter, for example, would more likely opt for an anabolic steroid such as Stanozolol (Winstrol) or Oxandrolone (Anavar), which are two anabolic steroids unable to convert into Estrogen and therefore the issue of water retention, and therefore the issue of added weight that would slow the athlete down is avoided. Many athletes may also elect to ‘stack’ anabolic steroids in a given cycle (stacking refers to the practice of combining more than one anabolic steroid in a cycle). In the case of cycle stacks, an individual might be able to increase the synergy and synergistic effects between the anabolic steroids to create a highly anabolic environment or to create a stack that might assist the user in favoring certain particular athletic or physique goals. These are some of the major reasons as to why the development of different types of steroids has been done.

It is actually quite ironic in the sense that the very first officially created derivative of Testosterone (Dianabol) was actually designed for the purpose of athletic performance in mind – not for the purpose of medical use.

The Importance of Using Testosterone as a Reference Point

A very small but extremely important note must be made for the reader to remember prior to discussing the various types of steroids and derivatives. It is extremely important to understand that Testosterone is utilized as the measuring stick (or the measuring bar) whereby all other anabolic steroids are measured against, referenced with, and compared to (much like the celsius scale of temperature measurement where the freezing point and boiling points of water are used as the baseline measurements for temperature). Upon understanding this, any individual can easily observe how a particular given anabolic steroid possesses an anabolic strength that might be several times stronger (or weaker) than Testosterone (Testosterone’s anabolic and androgenic ratings are both respectively 100). The importance of the anabolic and androgenic strength ratings of 100 respectively is paramount to understanding the different strengths of the various types of steroids.

Testosterone Analogues (Or Testosterone Derivatives)

As previously mentioned in the latter part of the introduction, all anabolic steroids in existence could ultimately be considered derivatives/analogues of Testosterone, but there are several direct derivatives of Testosterone that exist. Derivatives of Testosterone will of course possess and exhibit some or many of the same properties of Testosterone, and this can present both advantages and disadvantages which will be explained and covered in detail here. The very first officially created Testosterone analogue is Methandrostenolone (Dbol), followed by Boldenone (Equipoise). These two analogues will be utilized here as examples.

The general characteristics of Testosterone derivatives are very similar to that of Testosterone: they all exhibit the ability to aromatize into Estrogen (a characteristic shared with Testosterone itself), and they all exhibit the ability to interact with the 5-alpha reductase (5AR) enzyme to become reduced to a stronger androgen. Although they do not reduce into Dihydrotestosterone like Testosterone does, they still interact with the 5AR enzyme and reduce to their own respective individual stronger androgens (Dianabol will reduce into Dihydromethandrostenolone and Boldenone will reduce into Dihydroboldenone). However, the reduction of these analogues into their respective stronger androgenic metabolites differs from Testosterone in that they are reduced into very small trace amounts (usually the result of the structural modifications allowing these anabolic steroid analogues to possess a lesser affinity to bind to the 5AR enzyme).

In terms of the actual structural modifications, we will first examine Dianabol (Methandrostenolone). Dianabol is basically Testosterone that has been methylated at carbon 17-alpha on its structure (this is simply the addition of a methyl group at the 17th carbon). This process, known as C17-Alpha Alkylation, allows the anabolic steroid to be administered orally and still have a measurably strong effect on the body. Without this modification, it is impossible for any anabolic steroid to survive liver metabolism in significant enough quantities to promote any measurable effects in the body – the result is that extremely miniscule amounts of the anabolic steroid reaches the bloodstream to perform its job. Dianabol also possesses a double-bond between carbons 1 and 2. All of these modifications are what grant Dianabol with its increases in anabolic strength and reduced androgenic strength in comparison to Testosterone.

Equipoise (Boldenone) is very easy to describe after understanding Dianabol. Equipoise is simply Dianabol without the methyl group attached to carbon 17-alpha. EQ possesses the double-bond between carbons 1 and 2. The fact that these two hormones operate very differently in the body is quite evident that is a very strong indication that the addition of a methyl group (C17-alpha alkylation) to the 17th carbon does more than just affect the hormone’s resistance to breakdown in the liver – it actually changes the effects and properties of the anabolic steroid. Dianabol itself possesses moderate Estrogenic activity in the body, while Equipoise possesses low Estrogenic activity in the body. It is very evident that the structural modifications to Testosterone that result in both Dianabol and Equipoise grant one of them lower Estrogenic activity than Testosterone itself, but does not eliminate it. This is an example of what has been mentioned earlier about various properties and traits passed down from the parent/progenitor hormone to the analogue/derivative hormone, and that sometimes it will not always be expressed exactly the same. Case in point: Equipoise.

Testosterone analogues, because of their ability to still exhibit Estrogenic activity at some level, will commonly be preferred by users as anabolic steroids that are utilized in bulking or mass-gaining cycles due to the fact that the water retention associated with it is typically undesirable during periods of cutting or fat loss. This is because the water retention can cause the physique to take on a bloated and soft look. Therefore, the use of compounds such as Dianabol is generally limited as such. But this is not to say that Dianabol cannot be utilized for fat loss or cutting. Any anabolic steroid can be utilized for any purpose. There is no such thing as the commonly claimed myth of ‘cutting steroids’, ‘fat loss steroids’, ‘bulking steroids’, or ‘lean mass steroids’. There exist no such possible things except for anabolic steroids that may be preferred for cutting, bulking, or lean mass depending on their attributes and properties that are associated with side effects that may be undesirable for the goal of cutting or bulking. This will be further explained in greater detail in the final section of this article, but it is important to touch upon this topic and leave this idea in the reader’s mind for the time being.

Dihydrotestosterone Analogues (Or Dihydrotestosterone Derivatives)

Quite simply put, Dihydrotestosterone analogues are different types of steroids that are derived from Dihydrotestosterone. These are anabolic steroids that essentially utilize Dihydrotestosterone as the base template for the modifications to the core Dihydrotestosterone chemical structure. The fact is that the majority of anabolic steroids are Dihydrotestosterone derivatives, because research and history has shown that Dihydrotestosterone analogues exhibit very promising results in the different changes and modifications that result in the different Dihydrotestosterone variants. Dihydrotestosterone derivatives belong to the family of DHT-derivatives (such as Winstrol, Anavar, Primobolan, Masteron and several others).

However, Dihydrotestosterone is a very unique anabolic steroid in the sense that it holds absolutely no activity within muscle tissue, which is a very interesting detail in and of its self. All anabolic steroids that belong to DHT-derivative family contain modifications to their chemical structures that grant them significant activity and effectiveness within muscle tissue, where DHT itself unmodified would never survive metabolism there. This is because Dihydrotestosterone, once it enters muscle tissue, is instantly deactivated and metabolized into two ineffective hormones by an enzyme. This enzyme is the 3-hydroxysteroid dehydrogenase enzyme, which is present in large quantities in muscle tissue, and is the enzyme that serves to metabolize any DHT that enters muscle tissue into two inactive metabolites:  3-Alpha Androstanediol and 3-Beta Androstanediol. These two hormones which are metabolites of DHT are not anabolic what so ever in muscle tissue. This is therefore the reason as to why DHT is not anabolic in muscle tissue at all, and many chemists and biologists believe that if this enzyme 3-hydroxysteroid dehydrogenase did not exist in muscle tissue, that DHT would actually be a very potent and powerful anabolic steroid.

The nature of DHT being a non-anabolic steroid is simply due to outside factors and has nothing to do with the properties and nature of the hormone itself. Therefore, it would be an error to simply refer to DHT as only an androgenic steroid. It indeed holds the capability to be anabolic, but it is unfortunately stripped of that experience as soon as it enters muscle tissue by the enzyme 3-hydroxysteroid dehydrogenase. The evidence that DHT is in fact a very anabolic hormone lies in the fact that its derivatives become anabolic due to the fact that their chemical modifications eliminate the affinity for the hormone to interact with the 3-hydroxysteroid dehydrogenase enzyme.

Masteron (Drostanolone) will be used as a simple example and explanation here. Masteron is essentially DHT with a methyl group at the 2nd carbon (known as carbon alpha) atom has been added. This modification is what is known to be responsible for the slight anabolic strength increase in comparison to Testosterone. This methyl group addition increases the anabolic strength by way of granting Masteron an increased resistance to being metabolized into inactive metabolites by the enzyme 3-hydroxysteroid dehydrogenase.

The typical traits and characteristics of DHT derivatives/analogues are those of an elimination of any possible interaction with the aromatase enzyme, thereby allowing all DHT derivatives to exhibit absolutely no estrogenic activity what so ever. The only exception to this case is Anadrol (Oxymetholone), where it possesses a high degree of Estrogenic activity, but this is not due to interaction with the aromatase enzyme – it cannot interact with the aromatase enzyme. Anadrol instead exhibits mysterious properties whereby it and its metabolites act as Estrogens themselves in various tissues in the body. But Anadrol is a special exception, not the rule.
DHT derivatives possess more versatility and flexibility in the preferred uses among bodybuilders and athletes than other types of steroids. This is because these anabolic steroids will exhibit no Estrogenic activity in the body, thereby avoiding side effects such as bloating and water retention, gynecomastia, and other Estrogen-related side effects. DHT derivatives and analogues are therefore preferred among bodybuilders for fat loss and cutting phases of dieting, where a lean and ‘hard’ look to the physique is desired over the soft, puffy, and bloated look that aromatizable androgens will commonly provide.


A positive note here on DHT derivatives is that they do not interact with the 5-alpha reductase enzyme (remember, the enzyme responsible for the conversion of Testosterone to the much more androgenic Dihydrotestosterone). This is because DHT derivatives have already been reduced due to their nature already as DHT derivatives, and so therefore there is no risk involved in these types of steroids converting to any metabolite that exhibits stronger androgenic effects. Therefore, the androgenic strength associated with analogues of DHT should be the androgenic strength that one should experience fairly consistently throughout use.

Nandrolone Analogues (or Dihydrotestosterone Derivatives)

There essentially exists only one Nandrolone derivative that is conventionally and commercially available: Trenbolone. Although other Nandrolone analogues have been developed, they are not commonly known and are not very popular for one reason or another. Nandrolone itself cannot technically be counted, as it is not a derivative – it IS Nandrolone. Therefore, the only Nandrolone analogue of question here is Trenbolone.

Nandrolone and Tren belong to a special unique category of anabolic steroids known as Progestins. Nandrolone itself is quite structurally similar to Testosterone. However, Nandrolone differs from Testosterone due to the lack of the 19th carbon. This is why Nandrolone and Trenbolone are often referred to as 19-nortestosterone compounds, meaning a carbon atom is missing at the 19th position. As such, any compound relating to (or is a derivative of) Nandrolone is also commonly referred to as a ’19-nor’ compound, including Nandrolone itself.

Trenbolone being a Nandrolone derivative is of course missing the aforementioned carbon atom at the 19th position (which is in reality a whole methyl group) and this carbon atom is instead replaced by double-bonds between the two carbon atoms that the 19th carbon was originally bound with (this
differs from Nandrolone where the lacking 19th carbon is simply replaced with a hydrogen atom instead of double-bonds in Trenbolone’s case). This lack of a 19th carbon is what increases the resistance of 19-nor compounds to interaction with the aromatase enzyme and therefore very resistant to any Estrogen conversion – however, this is not the whole story for Trenbolone when it comes to aromatization. Trenbolone also contains modifications at carbons 19 and 11, where one hydrogen atom was removed from each carbon so that carbons 19 and 11 become double-bonded with their neighboring carbon atoms in their respective cycloalkane rings. These additional modifications of double-bonds at carbon 19 and 11 are what provides Trenbolone not just increased resistance to aromatization, but to become completely immune to it and be unable to interact what so ever with the aromatase enzyme. These different modifications are also responsible for granting Trenbolone with the extreme anabolic and androgenic strength ratings it is so well known for.

19-nor Progestational compounds such as Nandrolone and Trenbolone exhibit various effects and side effects in the body that are unique only to 19-nor compounds, and are not seen among any other types of steroids. Studies have demonstrated that 19-nor anabolic steroids tend to exhibit binding affinity for the Progesterone receptors in the body[1]. Trenbolone in particular possesses very strong binding affinity (much stronger than Nandrolone) for the Progesterone receptor[2]  1. As mentioned above, this is one of the factors involved where Trenbolone possesses side effects that are almost never seen in other anabolic steroids that are not Progestins. Progestogenic side effects are almost identical to Estrogenic side effects, and they include: severe endogenous Testosterone production shutdown/suppression, gynecomastia, and water retention. It has been determined that the activity of Progestins is closely correlated with the activity of Estrogen in the body. This is why care must be taken to understand the Progestogenic properties of Nandrolone and its derivatives before using them, as well as how to properly deal with the associated Progestogenic effects.

19-nor compounds (Nandrolone derivatives) are preferred by athletes and bodybuilders for many of the same reasons that they would prefer DHT derivatives. 19-nor compounds are either highly resistant to aromatization, or do not aromatize into Estrogen at all (in Trenbolone’s case), and therefore eliminate the potential for Estrogen-related side effects such as water retention/bloating and gynecomastia. These types of steroids also do not interact with the 5AR enzyme, or they interact with it in very miniscule amounts (in Nandrolone’s case). However, Progestogenic effects are a concern that must be fully understood. For a further in-depth description of what these Progestin effects are, please refer to the specific profiles for both Nandrolone as well as Trenbolone where this is delved into greater detail.

The Myth of Anabolic Steroids for Bulking and/or Cutting

Finally, the myth that there are various anabolic steroids specifically for ‘bulking’ and/or specifically for ‘cutting’ must be addressed. It first must be made perfectly clear that Anabolic steroids do not directly burn fat, as they instead simply increase nutrient partitioning. Nutrient partitioning is defined as the effect of directing/shuttling ingested nutrients, vitamins, and minerals towards muscle repair and muscle growth to a large degree – so much so that fat storage is either completely avoided or dramatically reduced. Anabolic steroids do not possess any direct effects on fat metabolism that would result in dramatic changes. It is understood that anabolic steroids do interact with androgen receptors on fat tissue to initiate lipolysis (fat breakdown), but this does not occur to any significant degree.

The ‘fat burning’ properties commonly associated with anabolic steroids stem from the aforementioned extreme level of nutrient partitioning they exhibit. Some types of steroids exhibit this at a far greater degree than any other anabolic steroid, especially anabolic steroids such as Trenbolone. Even Testosterone does this, where cases have been observed whereby an individual engaging in their first-ever cycle of Testosterone results in the gaining of lean mass, and a reduction of varying degrees of body fat percentage.

Of course, the most prominent detail to be reminded of is the fact that results are 100% dependent on the individual’s nutrition and training. Different types of steroids merely serve to amplify the efforts and hard work that the nutrition and training aspects have properly established. For example, if an individual’s primary goal of fat loss is desired, then the individual’s nutrition must reflect that by either engaging in a caloric deficit or some sort of nutritional plan that favors fat loss. Although various anabolic steroids might also exhibit effects and properties that favor bulking or mass gaining cycles, such as Dianabol or Anadrol for example, it does not mean that they cannot be utilized for the purpose of fat loss or cutting as well. It is the individual’s diet that will determine whether he or she experiences fat loss or muscle gain. The decision for most athletes to refrain from the use of compounds such as Dianabol for fat loss rests solely on the fact that Dianabol exhibits Estrogenic activity that results in water retention and bloating, resulting in the puffy, bloated, and soft look to the physique that is not desired during fat loss phases. With that being said, one could easily work around this limitation with the inclusion of an aromatase inhibitor, but the general rule remains: nutrition and training determine results, not the types of steroids used.



Medical References:


[1] Endogenous nandrolone production: studies in granulosa cells from patients with polycystic ovary syndrome (PCOS). W. Schanzer, H. Geyer, A. Gotzmann, U. Mareck (eds.). Sport und Buch Strauss. Koln (2005) 483-486.

[2] Studies of biological activity of certain 19-nor steroids in female animals. Pincus G, Chang M, Zarrow M, Hafez E, Merril A. December 1956

[3] Characterisation of the affinity of different anabolics and synthetic hormones to the human androgen receptor, human sex hormone binding globulin and to the bovine progestin receptor. Bauer, Meyer et al. Acta Pathol Microbiol Imunol Scand Suppl 108 (2000):838-46.