There is conflicting info on the internet, e.g. "Melatonin inhibits the enzymes involved in the synthesis of estrogen, thus leads to lower levels of estrogens. It is thus considered to be a selective estrogen enzyme modulator. In a study on 3,699 post-menopausal women, the results show that...
In a 2022 interview Dr R said he was 87 and took 80 mg. 3 doses;- 45 mins before bedtime, then 15 mins before, and final dose at bedtime. Start taking it after 40 years at 10 mg.