Diindolylmethane has potent effects on estrogen metabolism and is able to prevent a huge increase or decrease of estrogen levels (1). In small amounts, it can both inhibit the enzyme that converts testosterone into estrogen and it can act on more potent forms of estrogen and convert them into less potent forms (2). This conversion lowers the effects of estrogen on the body. However, taking too much at once can actually induce the aromatase enzyme and act in the opposite manner and increase estrogen synthesis.
1 – Riby, J. E., Chang, G. H., Firestone, G. L., & Bjeldanes, L. F. (2000). Ligand-independent activation of estrogen receptor function by 3, 3′-diindolylmethane in human breast cancer cells. Biochemical pharmacology, 60(2), 167-177.
2 – Leong, H., Riby, J. E., Firestone, G. L., & Bjeldanes, L. F. (2004). Potent ligand-independent estrogen receptor activation by 3, 3′-diindolylmethane is mediated by cross talk between the protein kinase A and mitogen-activated protein kinase signaling pathways. Molecular Endocrinology, 18(2), 291-302.