Hormones present in the blood

The level of SHBG present in the body is also variable and can be altered by a number of factors. The most prominent seems to be the concentration of estrogen and thyroid hormones present in the blood. We generally see a reduction in the amount of this plasma binding protein as estrogen and thyroid content decreases, and a rise in SHBG as they increase. A heightened androgen level due to the administration of anabolic/androgenic steroids has also been shown to lower levels of this protein considerably. This is clearly supported by a 1989 German study, which noted a strong tendency for SHBG reduction with the oral anabolic steroid stanozolol (Winstrol).
After only 3 days of administering a daily dose of 2mg/kg body-weight (about 18mg for a 200lb man), SHBG was lowered nearly 50% in normal subjects. Similar results have been obtained with the use of injectable testosterone enanthate; however, milligram for milligram, the effect of stanozolol was much greater in comparison.
The form of administration may have been important in reaching this level of response. Although the injectable was not tried in the German study, we can refer to others comparing the effect of oral vs. transdermal estrogen. These show a much greater response in SHBG levels when the drug is given orally. This is perhaps explained by the fact that SHBG is produced in the liver. Therefore, we cannot assume that injectable Winstrol (or injectable steroids in general) will display the same level of potency in this regard.