Hypothyroidism (or underactive thyroid)
- When your thyroid gland doesn’t make enough thyroid hormone
- May cause weight gain, constipation, slowed heart rate, dry skin and hair, sensitivity to cold
Hyperthyroidism (or overactive thyroid)
- When your thyroid gland makes too much thyroid hormone
- May cause weight loss, nervousness, frequent bowel movements, sensitivity to cold, and muscle weakness
Both
- More likely to affect women
- Symptoms like fatigue and an enlarged thyroid, also called a goiter, which may make your neck look swollen
- Can be caused by autoimmune diseases, which cause your body to attack itself