Nonspecific. The s+s of thyroid disease are nonspecific. Hypothyroidism typically causes fatigue, weight gain, feeling cold, constipation, heavy periods, sleepiness. Hyperthyroidism causes weight loss, anxiety, tremors, fast heart beating, feeling hot, frequent bms, light periods, muscle weakness. However, most people with any one or combination of these symptoms have no thyroid problem at all. Get tested.