Hypothyroidism is a condition where the thyroid gland fails to produce enough thyroid hormones, which are vital for regulating metabolism, energy, and overall body function. Common causes include autoimmune disorders like Hashimoto's thyroiditis, iodine deficiency, or thyroid surgery. Symptoms often develop gradually and may include fatigue, weight gain, cold intolerance, dry skin, hair thinning, depression, and a slow heart rate. It is diagnosed through blood tests measuring thyroid-stimulating hormone (TSH) and free T4 levels. Treatment typically involves daily thyroid hormone replacement therapy with levothyroxine, which helps restore normal hormone levels and alleviates symptoms. Proper management, including regular monitoring and a healthy lifestyle, is essential to prevent complications and maintain well-being.