The symptoms may vary depending on the thyroid function, i.e. hyperthyroidism or hypothyroidism. Hyperthyroidism can cause sweating, rapid heart rate, anxiety, tremors, fatigue, difficulty sleeping, sudden weight loss, and protruding eyes.[2] Hypothyroidism can cause weight gain, fatigue, dry skin, hair loss, intolerance to cold, and constipation.[2] The effects of this disease may be permanent but can sometimes be transient. Symptoms may come and go depending on whether the person receives treatment, and whether the treatment takes effect.