Hashimoto's Disease is an autoimmune disorder where the body's immune system mistakenly attacks the thyroid gland. This gland, located in the neck, produces hormones that regulate metabolism, energy levels, and overall health. When damaged, it can lead to an underactive thyroid, known as hypothyroidism, causing symptoms like fatigue, weight gain, and depression. People with Hashimoto's may experience fluctuations in their thyroid hormone levels, leading to various health issues. Diagnosis typically involves blood tests to check hormone levels and the presence of antibodies. Treatment often includes thyroid hormone replacement therapy to help manage symptoms and restore normal hormone levels.