What raises TSH?

This is likely such an ABC question, but I figured this is likely the best place to ask it.

I got diagnosed with Hashimoto’s in May and my TSH was around 4.7. I started NP Thyroid, and it dropped down to around 3.0 (in June). I just got blood work done again and my TSH was back at around 4.1. My doctor wants to kick my meds up a notch, which I will totally do, I think I just wanted to understand why TSH rises. Is it just the normal progression of HM? Did I do anything to cause it to rise? Does food play a role? My doc was a little unclear, so I wanted to ask here too.