Can hyperthyroidism cause chronic low grade fevers of about 98.7-99.6? and what else could it cause?

Not usually: Fever is not a usual symptom. Most often hyperthyroidism causes increased sweating, rapid heartbeat or palpitations, a tremor, the appearance of staring, loose stools, fatigue or shortness of breath with exercise, weight loss, and feelings of anxiety.

Likely U R right..: Excess thyroid hormone causing thyrotoxic crisis, aka thyroid storm, can cause elevation of body temperature in excess of 104, so chronic hyperthyroidism is likely to elevate your body temperature a bit. Your body is basically revved up 24/7 thus producing extra heat, hence the temperature. Please consult doc to get treatment as untreated can cause problems for you. Good luck.