Most goiters are caused by an overproduction of thyroid hormones or stimulation by external factors. There are two types of goiter: physiological and pathological. Physiological goiter is common during adolescence, lactation, pregnancy, menopause and other special periods. Due to the rapid metabolism of the body, the need for thyroid hormones increases, resulting in increased secretion of thyroid stimulating hormones, resulting in a large thyroid gland. Pathological thyroid enlargement is commonly caused by hyperthyroidism, hypothyroidism, thyroiditis, thyroid tumors and other diseases. Congenital or acquired defects in certain enzymes in the process of thyroid hormone synthesis can also cause a large thyroid gland. Regular smoking can also sometimes cause a thyroid enlargement due to the presence of thiocyanates in inhaled substances. Some genetic factors and drinking contaminated water can also cause an enlarged thyroid gland; autoimmune diseases can also cause an enlarged thyroid gland; and sometimes viral colds can also cause an enlarged thyroid gland. There are many causes of a large thyroid gland, so you will need to go to the hospital to get a diagnosis of what is going on.