Thyroid disease is said to occur when the thyroid gland, located in the neck below the thyroid cartilage or Adam`s Apple, produces either a more or lesser amount of hormone required by the body. The thyroid hormone is responsible for regulating various body functions such as growth, metabolism, etc. In case the thyroid gland becomes hyperactive, it releases an excess amount of thyroid hormone into the bloodstream, resulting in Hyperthyroidism and in another case it may release a fewer amount of thyroid hormone in the bloodstream resulting in Hypothyroidism. Both the conditions affect the normal chemical activity of the cells and result in disturbed body functions such as metabolism. Whether a person has hyperthyroidism or hypothyroidism, the thyroid gland becomes enlarged in both cases. An enlarged thyroid gland can be felt in the neck as lumps under the skin. Other than hyperthyroidism and hypothyroidism, some other thyroid diseases are thyroid cancer, non-cancerous thyroid nodule, congenital anomalies, etc. Hyperthyroidism: Hyperthyroidism or overactive thyroid disease is caused by overproduction of T?3 and T4 hormone, and it is generally caused by the development of Grave`s disease, an autoimmune disease. Under the condition of Grave`s disease, the immune system produces abnormal antibodies that make the thyroid gland produce more thyroid hormone than usual. Hyperthyroidism is more likely to occur in women than in men, teens and middle-aged adults. People with hyperthyroidism may experience weight loss, even if they eat more than normal. Some other symptoms of the disease are fatigue, difficulty in sleeping, protruding eyes, thyroid goiter, sweating, muscle weakness, intolerance to heat, abnormal menses in girls, etc. Hypothyroidism: Hypothyroidism is a thyroid disease that results due to the underproduction of T3 and T4 thyroid hormones. It generally results due to an autoimmune disease called Hashimoto`s thyroiditis, congenital thyroid abnormalities or the removal of the thyroid gland in surgery, etc. Initially, the condition presents no symptoms at all but at advanced stages, it may present some common symptoms such as feeling depressed or sluggish, weight gain, baldness, cold intolerance, muscle weakness, dry hair, etc. It also affects the normal growth rate of an individual. Thyroid Cancer: Thyroid cancer is more commonly found in women than in men and there is no known cause of the disease. However, it may occur due to a family history of goiter, exposure to radiation, or other hereditary conditions. It is generally diagnosed with needle biopsy or through other radiology techniques. Thyroid Nodule: Thyroid Nodules are identified by the presence of a lump or enlarged areas in the thyroid gland. Most of the thyroid nodules are non-cancerous. Thyroid diseases are really very common these days due to a modified lifestyle and if the disease is not diagnosed at initial stages, they can result in severe ones. If you experience frequent weight loss or weight gain or any other above specified symptom, consult your physician. It might be possible that you have developed any of the thyroid diseases stated above. Women are more prone to thyroid abnormalities as compared to men, so they should pay special attention.