Hello dear friend..I have gone through your question.. The issue can be because of the underlying hypothyroidism which is quite common in hilly areas. Dietary iodine deficiency is also a cause for hypothyroidism especially in hilly areas. The causes for thyroid gland enlargement are 1.In an attempt to extract more iodine from blood, the gland enlarges in area and tires to trap iodine from blood. 2. As iodine is the key element in thyroid hormones: tri-iodothyronine (T3) and tetra-iodothyronine, in hypothyroidism the level of T3 and T4 in body will be low. There is a feedback mechanism in our body involving the hypothalamus(structure in brain)-pituatary gland(inside the cranial cavity)-thyroid gland which keeps the hormone levels within normal limits in our body. When the T3-T4 levels are low pituatary tries to stimulate thyroid gland to produce more T3 and T4 by producing another hormone Thyroid stimulating hormone(TSH). TSH also causes the gland to enlarge. My advice for you is a) kindly do a complete thyroid function test and make sure all are within normal limits, if not you have to increase the dose of your medicine as advised by your physician b) Also it will be better if you could have a fine needle aspiration study of the enlarged gland and get a cytology opinion.