Here's an excerpt from one of the few papers(Endocrinology Vol. 145, No. 12 5417-5419)
The current report by Gao et al. (9) describes the tissue selectivity in intact male rats of two SARMs, designated S1 and S4, that behave as partial agonists in androgen-responsive tissues, such as prostate and seminal vesicles, but full agonists in anabolic tissues such as the levator ani muscle (12). Both S1 and S4 bind with high affinity to AR, with dissociation constant of the ligand inhibitor-receptor complex (Ki) values of 6.1 and 4.0 nM, respectively; which is similar to T, much higher than hydroxyflutamide (Ki = 25 nM), but lower than DHT (Ki = 0.2 nM). In immature castrated rats, S1 and S4 exhibited full AR agonist activity in levator ani muscle but only partial agonist activity in prostate and seminal vesicles. The relative rates of efficacy of S1 and S4 in prostate were 12 and 29%, respectively, compared with T propionate. As reported by Gao et al. (9) for intact male rats, S1 selectively decreased prostate weight with efficacy similar to that of the 5{alpha}-reductase inhibitor finasteride without affecting the levator ani muscle or altering the plasma levels of T, LH, or FSH. By contrast, hydroxyflutamide decreased both the prostate and levator ani muscle weights without selectivity and increased plasma hormone levels in a dose-dependent fashion. Neither S1 nor S4 affected 5{alpha}-reductase type I or II isozyme activities. These results show that S1 and S4 act as partial AR agonists with tissue-selective activity that suppresses androgen-dependent prostate growth without influencing the anabolic effects of T on weight of the levator ani muscle. Moreover, the maintenance of normal serum T levels and lack of effect of S1 and S4 on pituitary gonadotropin secretion further exemplify the tissue selectivity of their action.
So what we learn from this is that sarm activity has high anabolic affinity, did NOT affect T levels and had adrogenic activity only in the positive respect of preventing prostate enlargement etc which occurs with highly androgenic AAS compound use....