Does hyperthyroidism cause low grade fever?

Yes. : The thyroid hormone is a permissive hormone that stimulates metabolic and catabolic cycles in your body. Hyperthyroidism subsequently enhances these cycles causing insomnia, heat intolerance, anxiety, chest palpitation, and possible low grade fever, etc. Now, all these symptoms can be controlled by medication. I recommend that you see an endocrinologist for further evaluation.