f Hypothyroidism, or an underactive thyroid, is a condition where the thyroid gland in your neck doesn’t produce enough thyroid hormones. These hormones regulate your body’s metabolism, so when levels are low, many bodily functions, including energy use and heart rate, slow down. Symptoms can include fatigue, weight gain, and sensitivity to cold, while common causes are Hashimoto’s disease (an autoimmune disorder) and iodine deficiency
