Androgenic and Anabolic Ratios Explained

In today’s Master Class we look at the “myotrophic–androgenic index” or what we bodybuilders and other recreational users of AAS call the “anabolic-androgenic ratio”and explain where the model describing them came from and the potential flaws in the model.

The model for these ratios were first defined by scientists Eisenberg and Gordan in 1950 and the measured ratio of growth in rats of the levator ani muscle and growth in the seminal vesicles following castration and the administration of various Compounds.

The problem with these early studies is that the levator ani muscle is not a skeletal muscle its a muscle, found in both sexes, that stretches from the pubic bone to the tail bone and in humans and envelopes the rectum.
additionally the levator ani muscle may actually reflect androgenic efficacy of AAS because it can be viewed as part of the reproductive system. Its use as a bioassay for “anabolic” activity has been questioned.

Other scientists  such as Hershberger have set out to define anabolic androgenic ratios of other compounds but utilized the ventral part of the prostate as a gauge for androgenic activity.

And now even 20 years later and scientists still debate whether or not the levator ani muscle is a good indicator of skeletal muscle tissue or which part of the prostate should be used to infer androgenic activity.

Similar issue exist with using  the seminal vesicles as a measure of Androgens as seminal vesicles react much slower to certain androgens, so for tests over short periods of time, data might be skewed towards a higher myotrophic (anabolic) effect vs the androgenic effects.

Some later studies proposed using nitrogen-retention assay but even that provides an extremely indirect measure of muscle deposition.

There has been virtually no investigation of the relative anabolic and androgenic properties of AAS since the mid-1970s and none using more modern tools to assess androgen receptor activity. One major goal of this chapter is to summarize recent developments in the molecular pharmacology of androgen receptors that are opening this area up for pharmaceutical development.

The takeaway from all this for Master Class Members is that many of the “anabolic androgenic ratios” we see quoted on bodybuilding websites are the result of numerous rat studies, that differ in the tissues types used to define anabolic vs androgenic activity – so there is variability in the testing models.

In addition, the concentration of androgen receptors may differ in rats vs humans within specific tissue types so although this is the best and most peer-reviewed information we have, we should not place too much weight in these ratings.

If you have any follow on questions be sure to ask !


Victor Black