To take hormones or not to take them...that, with apologies to Shakespeare, is the question faced by today's athletes. Testosterone magazine is supremely interested in prohormones. I mean, with just a few little tweaks and manipulations, the athletic world could really have something phenomenal on its hands. Trouble is, like a fresh watermelon seed being pinched by a child's hands, the science has squirted away from the industry. In order to try to look at the subject objectively and scientifically, we asked technical writer and scientist-type person Stephanie Porter to look at the prohormone literature; all of the literature, and give us her appraisal. We think she's done a damn good job.
Before we delve into the world of prohormones, it might be a good idea to first talk about sources of information, because all sources aren't equal. It's important to understand the difference between a peer-reviewed publication and everything else, because information that appears in a magazine, advertisement, or newsgroup isn't necessarily correct or accurate (like you needed to be told that).
A peer-reviewed scientific article is one that has been read and critiqued by at least two (often three) scientists that are experts in the field, and then accepted for publication based on those reviewer comments. Almost any medical or scientific journal is peer-reviewed. Of course, this doesn't mean that the interpretation of the data is always correct because even scientific articles have to be read with an inquiring mind, but at least it's a step in the right direction. However, information you see presented outside of this venue isn't necessarily peer-reviewed and consequently, should be looked at with at least a hint of suspicion. Even abstracts and talks presented at a scientific meeting can't be accepted as accurate until the data appears in a scientific or medical journal. The info simply hasn't been peer-reviewed. Furthermore, they might be presenting preliminary data that hasn't been double-checked. The information could quite possibly be inaccurate or just plain wrong. There are also different types of studies and the results of one type can't necessarily be applied to another. For instance, an in vitro study is conducted on either isolated enzymes, cell extracts, or cells that are grown out of the body in a culture dish. These studies are good for following biochemical or molecular pathways, but they don't always reflect what happens in a whole animal. Conversely, there are in vivo studies using animals, and these can give results that can theoretically be applied to humans, but animals can differ dramatically from humans in their response to chemicals. As such, caution is required when applying the results to people. Studies with human subjects can be set up in multiple ways, some better than others. A study involving just a few people, with no control group, may not reflect the true consequences of administering a compound, because the placebo effect may be large (Clarkson and Thompson, 1997). A double-blind placebo controlled study, in which neither the subjects nor the researchers know who got which substance, is much more believable and that's why the method has been a standard in medical research. Of all the methods used, the double-blind crossover is the gold standard in hormone research. This is a double blind study in which the placebo (control) and experimental groups switch halfway through the trial. Take for instance, steroid studies where the participants can often tell which group they're in due to the noticeable side effects of taking steroids. Using a crossover approach helps to minimize that problem. Now that you have a better idea of various type of research methods used, you're in a better position to evaluate any studies.
A little bit of biochemistry
Before we take a look at the prohormone body of research, let's rehash a few basics about steroids in general. If you're an expert in the subject, just skip the following paragraph. Steroid hormones work by interacting with a steroid-specific receptor in the cell. The receptor is a protein to which the steroid binds; the steroid fits into a pocket on the receptor that is designed to accept the hormone like a lock and key. The receptors, in turn, are special proteins called transcription factors. Transcription is the process by which genes are expressed using the DNA "blueprint" as a template for the eventual construction of a specific protein and transcription factors control the process of transcription. Steroid hormone receptors aren't active until the steroid hormone is bound. By activating transcription of specific genes, hormones (through their receptors) can change the milieu of proteins within cells, and this can lead to major changes in the body such as building muscle or building breast tissue. The ideal steroid hormone would have anabolic, or muscle-building, activity without androgenic activity, since the androgenic activity is associated with undesirable side effects such as infertility, hair loss, acne, increased risk of prostate disease, and more toxic effects like cardiovascular or liver disease. Furthermore, the ideal steroid would have no estrogenic effects because, among the side effects, is gynecomastia. Unfortunately this ideal steroid does not exist, probably because anabolic and androgenic effects are both regulated by the androgen receptor. Since prohormones behave much like steroids (and in some cases are technically steroids) they have many of the same problems.
The prohormone meat and potatoes
Listed below are the prohormones that will be discussed in this article. I've also included some their aliases, along with the abbreviations used in the rest of this article (in parenthesis). I'll first summarize the relevant scientific literature on each, and then present non-peer reviewed information. Where, you might ask, are the double-blind crossover studies? There aren't any. There are no published medical studies about the use of prohormones for the purposes of building muscle. If you're the kind of person that doesn't like to take a substance before research studies on safety and effectiveness have been done, you can stop reading right here and forget about prohormones until the medical studies come out.
The major prohormones Androstenedione (Adione)
Also called:
• 4-androstenedione,
• 4-androstene-3,17-dione 4-Androstenediol (4-AD)
Also called:
• 4-androstene-3beta,17beta-diol
• 4-androstene-3alpha,17beta-diol
• androst-4-ene-3beta,17beta-diol
• androst-4-ene-3alpha,17beta-diol
• D4-androstenediol 5-Androstenediol (5-AD)
Also called:
• 5-androstene-3beta,17beta-diol
• 5-androstene-3alpha,17beta-diol
• androst-5-ene-3beta,17beta-diol
• androst-5-ene-3alpha,17beta-diol
• D5-androstenediol 19-Norandrostenedione (19-Nordione)
Also called:
• 4-oestren-3,17-dione
• 19-nor-4-androstenedione 19-Nor-androstenediol (19-Nordiol)
Also called:
• 19-Nor-4-androstene-3beta,17beta-diol
• 19-Nor-5-androstene-3beta,17beta-diol
A note on the alpha and beta nomenclature: Steroids are chemical structures composed of four rings made of carbon atoms. The rings, for simplicity, can be thought of as lying sideways on a plane, as if they were flat on a table. There are functional groups that can be made of different combinations of atoms (i.e. carbon or oxygen), that attach to the rings. These functional groups can either protrude above the plane of the rings (beta side) or below the plane of the rings (alpha side). The alpha and beta isomers can have very different behaviors, as will be discussed later.
Androstenedione
There's almost nothing in the medical literature about the safety or effectiveness of administering androstenedione to human subjects. Androstenedione is a precursor of testosterone and estrone, so it's possible that it's converted to both in humans (Abramowicz, 1999). One study found that taking a 100-mg dose resulted in a four- to six-fold increase in testosterone blood levels after one hour, but this study only involved two women. Data from a German patent showed oral Androstenedione increased blood testosterone levels by 111-237% using a 100-mg dose (Abramowicz, 1999). Both of these, however, are preliminary studies that don't determine if Androstenedione has an effect on muscle mass during weight training. Side effects such (such as gynecomastia) or safety issues weren't addressed, either. Truth be told, Androstenedione has been shown to convert to testosterone in vitro. An early experiment measured the conversion of various steroid derivatives after incubation with isolated human blood (Blaquier et al., 1967). In this study, Androstenedione was incubated with the blood and 5.61% was converted to testosterone in men, while 8.8% was converted to testosterone in women. This study shows blood can convert Androstenedione to testosterone, but again, it doesn't say anything about what would happen to organs such as the liver, which are involved in metabolic conversions. As mentioned above, Androstenedione can also convert to estradiol, so it's possible it will have estrogenic effects. In an in vitro cell culture system, using pig granulosa cells, Androstenedione was shown to convert readily to estradiol. This conversion probably occurred through an aromatization reaction (Rodway et al. 1999). Additional research on androstenedione had been reported on some of the newsgroups, but none of this research is yet published in peer-reviewed journals. I only report it here so you can look for the references to be published in the future and then make informed judgments about them. There was, for instance, a recent talk presented at a FASEB meeting (April 17-21 1999) from the laboratory of Robert Wolfe at the University of Texas, Galveston Medical Branch. The abstract was titled "Androstenedione does not stimulate muscle protein synthesis" and it reportedly demonstrated that androstenedione — given to male subjects — resulted in protein breakdown, not buildup, along with an increase in estradiol. This paper has been submitted for review and it's scheduled to come out within the next year, if it's accepted (Dr. R. Wolfe, personal communication). Another study is supposed to come out in Journal of the American Medical Association in June 1999, and it also reports an increase in estradiol levels in male college athletes, but not testosterone levels. In summary, it seems that there's very little known about the safety of androstenedione in humans, and there's nothing in the literature that shows Androstenedione can promote muscle growth. Androstenedione can be converted to both testosterone and estradiol in vitro, which could mean it'll have estrogen-like side effects when taken regularly. While there are rumors of recent human studies, these haven't been published yet, so they shouldn't necessarily be used as a basis for decisions about the drug.
5-Androstenediol
5-AD can be produced from DHEA and can be converted into testosterone. It's probably the prohormone that appears most often in the literature. Some early studies showed that 5-AD can indeed be converted into testosterone. In isolated rat testis tissue, 5-AD was converted into testosterone (Inaba et al., 1966). The same thing was seen in rat brain and pituitary tissue (Perez, et al., 1977). Although there is evidence that 5-AD can convert to testosterone and even activate the androgen receptor (Miyamoto et al., 1998), there's accumulating evidence that it also has estrogenic effects. For instance, 5-AD can induce synthesis of a fetal enzyme, called thymidine kinase (TK), in the rat uterus and this synthesis is also induced by estradiol (Leroy, et al., 1988). In fact, 5-AD produces its effects through binding to the estrogen receptor. This means 5-AD can act like estrogen without being converted into an estrogen-related product. 5-AD was however, less effective at inducing TK production than estradiol in these experiments, requiring more time at a higher concentration (meaning that its binding to the estrogen receptor is probably less efficient than the binding of estrogen is). Another study in rats revealed 5-AD also showed classic estrogen effects by increasing uterine weight when given as an implanted pellet (Seymour-Munn and Adams, 1983). 5-AD also stimulates the proliferation of MCF-7 cells, a human breast cancer line that divides in the presence of estrogens (Hackenberg et al., 1993). Interestingly, in the same study, 5-AD also inhibited the growth of a cell line that is normally inhibited by androgens, further demonstrating its ability to work as an androgen or estrogen, depending on the context. Finally, it's been shown in a recent epidemiological study that the presence of 5-AD correlates with the risk of beast cancer in post-menopausal women, i.e., woman with higher levels of 5-AD in their blood are more likely to develop breast cancer than women with low levels (Dorgan, et al., 1997). To summarize these results, although there are no published studies that look at the use of 5-AD for the purposes of building muscle, a number of studies show 5-AD to have a dual estrogenic/androgenic nature, which might be detrimental to any intended anabolic uses. Furthermore, its correlation with breast cancer risk in post-menopausal women and the fact that it stimulates growth of breast cancer cell lines is a note of caution to prospective users.
4-Androstenediol
It's clear that 4-AD can be converted to testosterone in vitro. As proof, Blaquier et al. looked at conversion of various steroids into testosterone by human blood (Blaquier et al., 1967). Here's a summary of their results for male blood donors: 4-AD-beta/beta
Testosterone: 15.76%
Androstene-dione: 0.18% Androstene-dione
Testosterone: 5.61%
Androstene-diol: 0.29% 5-AD
Testosterone: 0.19%
Androstene-diol: 0.14%
DHEA: 2.03%
These results demonstrate that 4-AD is converted more efficiently to testosterone by human blood than any of the other compounds, but it also shows that it also produces Androstenedione (as does testosterone), which, as discussed above, may show estrogenic effects. Another in vitro study using chick liver extracts looked at the conversion of 4-AD-beta/beta and 4-AD-alpha/beta into various products when incubated with the liver extracts (Ungar et al., 1956). Interestingly, both isomers of 4-AD formed testosterone but the testosterone production peaked and began to decline at the same time as the Androstenedione levels began to rise. It appears from these experiments that the 4-AD isomers did produce testosterone, but the testosterone was subsequently converted into Androstenedione. There wasn't much difference between the two isomers, except that 4-AD-alpha/beta produced an earlier testosterone peak (about 7 minutes) than did 4-AD beta/beta (30 minutes). However, there was a difference between the two isomers in one study (Dorfman et al., 1962). 4-AD-beta/beta and 4-AD-alpha/beta were used in the chick's comb test, where subsequent growth of the comb is a measure of androgen activity. When these isomers were injected or given orally, they both had an effect similar to that of testosterone. But when the compounds were applied directly to the comb, the 4-AD-alpha/beta isomer was much less active than either the 4-AD-beta/beta or testosterone. This suggests that there could be biological differences between 4-ADbetra/beta and 4-AD-alpha/beta, so any human studies will need to take this potential difference into account. Another recent paper examined the growth effects of an alpha/beta pair of 5-AD isomers (Huynh and Loria. 1997). The study found that 5-androstene-3beta,17alpha-diol inhibited the growth of mouse cancer cell lines while its isomer, 5-androstene-3beta,17beta-diol did not. These results emphasize that the position of functional groups (above or below the plane of the rings) can have a profound effect on the activity of a compound. Finally, there was a study that compared the binding of various steroid compounds to the estradiol receptor (ER) in human mammary cancer tissue (Poortman et al., 1977). Binding to ER is an indication of the possible estrogenic effects of a steroid. Here is a summary of the results: 19-Nor-diol
Relative binding to ER: 4.0% 5-AD-beta/beta
Relative binding to ER: 2.4% 4-AD-beta/beta
Relative binding to ER: 1.9% Testosterone
Relative binding to ER: 0.02% Androstene-dione
Relative binding to ER: <0.001%
Two interesting conclusions can be derived from this table. First, 5-AD has an only slightly higher affinity for the ER than does 4-AD (by about 20%). This is interesting in light of the demonstrated estrogenic effects of 5-AD. Also, 19-Nordiol has an even higher affinity for the ER, in fact, 60% higher than 5-AD (see below). In a recent issue of Testosterone, Pat Arnold promoted 4-AD as the prohormone of choice (see issue 27, Nov. 13, 1998). Unfortunately, there's nothing in the scientific literature regarding administration of 4-AD to human. What about unpublished results that have been reported to the public? Pat Arnold reported that in studies done by Tim Ziegenfuss at Eastern Michigan University, 4-AD caused a 310% greater increase in total testosterone than did Androstenedione, at 90 minutes after administration. They used 100 mg each 4-AD, Androstenedione, and placebo. The actual data wasn't presented and this study hasn't yet been published. Somewhat conflicting results appeared in a study by Earnest et al., Journal of Parenteral and Enteral Nutrition, 1999 vol. 23(1):S16. This group used a double-blind crossover study and reported that Androstenedione produces more free testosterone in serum than does 4-AD, and about the same level of total testosterone. Again, this information is in abstract form only, so it should be considered as preliminary. In summary, 4-AD can convert to testosterone more efficiently than 5-AD or Androstenedione in vitro. Whether this has any relevance to testosterone production in human subjects remains to be seen. Also, the potential estrogenic effects of 4-AD need to be carefully studied, since 4-AD can convert to Androstenedione in vitro and bind to the estrogen receptor. In addition, there's some evidence that the 4-AD-beta/beta and 4-AD-alpha/beta isomers have somewhat different biological effects. Obviously more studies need to be done to determine the anabolic effectiveness of 4-AD, along with its safety.
19-Nordione and 19-Nor-5-androstenediol
There's really nothing in the medical literature about the Nor compounds, 19-Nordione and 19-Nordiol. 19-Nordione is related to Androstenedione because it's similar in structure but missing a functional group as compared to Androstenedione (the methyl group at position 19 in the ring). 19-Nordiol is related to 5-AD in the same way. The Nor compounds are metabolized into nortestosterone (nandrolone) rather than testosterone. There's evidence that nortestosterone has a higher anabolic activity in relation to its androgenic activity than does testosterone (Engel et al., 1957, Sunduram et al., 1995). This, as Pat Arnold suggested in the aforementioned article, is not necessarily good as the Nor compounds can result in significantly decreased libido. One study looked at the effect of 19-Nordione on the conversion of Androstenedione to estrogen in human breast cancer cell lines. They found that both 19-Nordione and 19-nortestosterone inhibited conversion of Androstenedione to estrogen in a dose dependent manner by inhibiting the aromatase enzyme that performs the conversion (Perel et al., 1988). It's possible that 19-Nordione will have less estrogenic effects than other prohormones when administered to people because it inhibits aromatase in vitro. In opposition to this possibility, Poortman et al., (1977) found that 19-Nordiol binds to the ER with a higher affinity than any of the prohormones, including 5-AD. This suggests that although the Nor compounds might have lower androgenic activity than their corresponding Andro compounds, they might also have a greater tendency to produce estrogen effects by directly activating the estrogen receptor, and that research on the use of these compounds should consider this possibility. In summary, there is nothing published in the scientific literature about administering the Nor compounds to human subjects, and their anabolic and health effects are not known.
Conclusion
Very little is known about the effects prohormones ultimately have in people. Although they might have anabolic effects, prohormones still haven't been shown to increase muscle mass in weight-training adults. Furthermore, their safety hasn't yet been evaluated, particularly their long-term safety. Most of the prohormones can either be metabolized into estradiol or used in a pathway that leads to the production of estrogens. Some of these compounds are even able to activate the estrogen receptor directly, possibly leading to estrogenic effects without the need for metabolism. There needs to be further investigation on prohormones — well controlled, scientific studies — to determine their efficacy for building muscle mass and their potential negative side effects. Remember that there's currently no scientific proof that taking any prohormone would help build muscle mass or increase athletic performance. In fact, there's evidence to the contrary; prohormones might actually hinder muscle-building progress. And in some cases, prohormones could even be the growth stimulus for certain kinds of cancer.
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