Women & Thyroid Disorders

Does anyone know whether your time of the month affects thyroid? It seems like the couple of days before that the Synthroid works only half as well as the weeks prior, then a few days after the start of my monthly friend it feels like I've taken a dose & a half (I haven't, I double checked).

Is this totally unrelated or has anyone else experienced something similar?
This is all still new to me & I'm still trying to figure it all out.

Thanks!
Frances