Grapefruit juice is a cyp450 and cyp19a inhibitor. I believe grapefruit juice interacts with metabolism of steroids metabolized through p-450nf so it could potentially peak estrone, estradiol, estriol or other certain hormone levels significantly depending on substance taken. One would have to research the substance to be certain. Grapefruit alone can also increase estrogen when on nothing I believe to to cyp450 and 19a.