Hypothydroidism, or underactive thyroid, is a condition in which thyroid gland produces less or no thyroid hormones. The causes of Hypothyroidism are - Autoimmune diseases - Partial or complete surgical ablation of thyroid gland - Use of radioactive iodine for treatment of head and neck diseases - Thyroiditis i.e. inflammation of thyroid gland - Medicines e.g. Amiodarone, Interferon Alpha, Lithium - Extreme increase or decrease in dietary iodine - Pathology or trauma to pituitary gland - Rare diseases e.g. Sarcoidosis, Amyloidosis The symptoms of Hypothyroidism are - Exhaustion and fatigue - Cold and clammy hands - Anxiety and depression - Constipation - Low metabolic rate causing weight gain - Muscle cramps - Muscle weakness - Confusion and loss of mental clarity