anyone have any problems with low thyroid levels or not taking thyroid pills before?

.. my girlfriend has went at least a month or two without taking her levithyroxin for her hypothyroiditis more than a few times in the past year, will this have a lasting effect on her if she doesnt take it regurally and anyone have experiences with thyroid problems or autoimmunehypothyroiditis before???

2 days ago
also, anyone know if low thyroid levels can impair the mind’s thinking abillities or cause someone to be moody???