i found this study rather intriguing for the fact that 2 men given melatonin had an increase in testosterone and decrease in e2. So this might be something that may need to be further explored as possible increase in e2 and possible esterone levels. It may also show how we get older melatonin levels decline and e2 could possible be a residual effect from this as well as protecting from testosterone depeltion as well..
Melatonin Administration Alters Semen Quality in Healthy Men -- Lubo****zky et al. 23 (4): 572 -- Journal of Andrology