Assertion : Less iodine intake causes goitre. Reason : Less iodine...

(a) : Simple goitre or endemic goitre is the enlargement of thyroid gland accompanied with cretinism or myxoedema. It occurs in case of hyposecretion of thyroxine. To compensate for lower secretion of thyroxine from cells, thyroid gland enlarges to accommodate more secretory cells. It is caused due to dietary deficiency of iodine. To form normal quantities of thyroxine about $1 \mathrm{mg} /$ week of ingested iodine is required in the form of iodides.