Hypothyroidism is a condition where the thyroid gland is underactive, resulting in insufficient thyroid hormones. Common causes are autoimmune diseases, certain medications, iodine deficiency, radiation treatment or surgery. It causes symptoms such as fatigue, weight gain, cold intolerance, dry skin and hair loss, constipation, depression and mood changes, muscle weakness. Diagnosis is establish by blood tests which include TSH (screening test), and T4 and T3 levels (free and total). Depending on the situation your provider may also order thyroid ultrasound or thyroid scan if a goiter or nodule is present. Hypothyroidism can affect many other organ systems in the body so it is important to diagnose and treat the condition. It is treated with thyroid replacement (e.g. Levothyroxine). Once you start thyroid replacement treatment it takes at least 4-6 weeks to see the effects and reflect in your blood tests. Once you are diagnosed with Hypothyroidism you will need to remain on thyroid replacement to maintain your levels and periodic followup with your provider is essential. Women are more likely than men to have this condition. Most cases of Hypothyroidism in this country are a result of Hashimoto's thyroiditis (autoimmune thyroiditis) and to confirm your provider may order thyroid antibodies (Anti-TPO, Anti-Thyroglobulin). Your prognosis is excellent as long as you remain on the thyroid replacement.