S4 Andarine, binds to the androgen receptor which creates an increase in the expression of genes associated in protein synthesis which would in turn increase lean muscle mass. Studies have shown S-4 preserves lean muscle mass as well as increasing it making it a great benefit to fighting osteoporosis and muscle degeneration. S-4 is known to be one of the strongest SARMS because of the huge amounts of strength, stamina, lean muscle mass, and vascularity that it produces. Research shows, S-4 is comparable to Winstrol but has been shown to provide better muscle gains and has very little side effects on joints. Research also shows there is no estrogen conversion. The one negative side effect research has shown is blurred vision although temporary happens due to the s-4 molecule binding to the eye receptor.