SERM's (Selective Estrogen Receptor Modulator) : These block certain estrogen receptors, ***ending on the drug, and dont actually lower estrogen in the blood. Estrogen is left to circulate with nowhere to go. Because of this, SERMS have a positive effect on cholesterol levels. They have a negative effect on IGF-1, so if bulking, only take them if totally necessary. They are good at blocking gyno. Commonly used during PCT, and less often used while cycling.