weather or not there is any proof, halos are harder on your liver.
The reason why Halotestin is so hard on the liver is because it has three chemical bonds to break down before the steroid becomes biologically active. These are: a 17-a methyl group, a 9-a fluorine, and a 11-OH group.
The chemical name for fluoxymesterone is androst-4-en-3-one, 9-fluoro11,17-dihydroxy-1,7-methyl-,(11b,7b)-. We see from the name all of the bonds -- that it has 17A methyl (17 alpha alkylated), which is toxic in and of itself, and usually the only bond ever discussed with regard to oral steroids (injectable winstrol is so alkylated).
But halo also contains 9 - alpha fluorine ( fluorine is used to protect substances from breaking down before they can be utilized by the body; sodium flouride is an example). This bond is also very toxic.
But there is still the11-Hydroxyl group to deal with, which must be enzymatically reduced to the corresponding 11-hydroxy derivative before becoming biologically active. This reaction is carried out by a distinct 11-hydroxysteroid dehydrogenase isozyme in the liver that operates in a reductive mode.
This process alone is very toxic to both the liver and the kidneys.