Same as the study - 600mg once a day in the AM, of N-acetyl-cysteine. It was clear after a few days that it made a difference, too.

Mind you, I've had a hysterectomy (kept ovaries) and take letrozole daily to manage symptoms along with following a strict gluten-free and isoflavone-free diet. There were other supplements I took pre-surgery that helped a lot for the endo pain (like DIM & Calcium-d-Gluconate), as I'm not able to take exogenous hormones (like progesterone) due to bad side effects.

Perhaps this will encourage the FDA to approve NAC as a supplement after taking it off the US market several years ago. My experience with it (in the EU) for decreasing inflammation (and therefore brain fog) from endometriosis has been fantastic, with virtually no side effects.