I am trying to remember, but It should not matter if you take it at night or not. It takes synthroid 21 days to get to full strength in our bodies so I cannot imagine why it would be be harmful to take it at night verses morning.
I take mine in the morning. I have a little ritual to take my pills so I always know if I took them or not. If my morning routine gets changed I have to look to see if I took my pills. More often than not, I missed taking them.
So plan on a time, take them then and keep to that schedule.