There are many reasons not to use it for PCT. I posted this in another thread pertaining to the smae type of sitaution.
(1) Acta Endocrinol (Copenh) 1974 Oct;77(2):380-6
The effect of mesterolone administration to normal men on the pituitary-testicular function.
Aakvaag A, Stromme SB.
"The reduction in total plasma testosterone and the unchanged free testosterone is probably due to reduced testosterone binding to SHBG."
So even though mesterolone competes with test for SHBG binding, the diplaced test is cleared from the system faster, resulting in no net change of free test, since as the authors point out:
"the MCR [metabolic clearance rate] is inversely related to the degree of protein binding."
Winstrol does the same thing. When 10mg/day was administered to normal men for 14 days, total testosterone, shbg and free test were all essentially cut in half. (1) Total test went from 22 to 10 nmol/L; SHBG from 21 to 10 nmol/L; and free test from 398 to 231 pmol/L. So again, even though total test and SHBG are dropping, so is free test.
That is kind of the point of having bound and loosely bound test. Up to a point anyway. An excess of SHBG can be bad. Free test is just metabolized too quickly, with the rate of metabolization increasing in proportion to the concentration of free test.
SHBG is interesting in itself. It appears to be much more than just a passive transporter for sex steroids in the blood. It has been shown for instance to both block the proliferative action of estrogen in mammary tissue in vitro, and prevent the normal upregulation of the progesterone receptor caused by estradiol (2). There evidently just hasn't been enough research done to know if there is any clinical significance to these actions
(1) Clin Endocrinol (Oxf) 1984 Jul;21(1):49-55
Alteration of hormone levels in normal males given the anabolic steroid stanozolol.
Small M, Beastall GH, Semple CG, Cowan RA, Forbes CD.
(2) Mol Cell Endocrinol 2001 Feb 14;172(1-2):31-6
The control of progesterone receptor expression in MCF-7 breast cancer cells: effects of estradiol and sex hormone-binding globulin (SHBG).
Fazzari A, Catalano MG, Comba A, Becchis M, Raineri M, Frairia R, Fortunati N.
Thank Nandi for that.