ESTROGEN | Phase 1
The CYP17A1 enzyme initiates the first step in estrogen production by converting pregnenolone and progesterone into estrogen precursors, including DHEA. The CYP19A1 enzyme is responsible for controlling the rate at which androstenedione and testosterone are converted to estrogen.
Once produced, circulating estrogen is converted via phase I detoxification enzymes:
CYP1A1: produces 2OH estrogen which is ‘weak’ in action and thought to be neutral or even beneficial to the body. This is the most favourable pathway in terms of estrogen metabolism.
CYP1B1: produces 4OH estrogen and generates harmful free radicals in the process. 4OH estrogen has stronger oestrogenic properties than 2OH estrogen and has been associated with undesirable estrogen-linked conditions and to DNA damage. As a result, this is the least favourable pathway of estrogen metabolism.
CYP3A4: produces 16OH estrogen, thought to be stronger than 2OH and potentially harmful, although further research needs to be done. As a result, this is thought to be a less favourable pathway.
Knowing which phase I pathway/s your body favours is useful since it gives a clue as to which forms of estrogen might be dominant in circulation and the diet and lifestyle measures you should take care to implement or avoid in order to maintain a healthy balance. This is truly empowering.