Grave's disease is related to which gland?

Graves' disease is caused by . . . . . . .

Exophthalmic goiter is caused by the hypersecretion of ..........

What happens if iodine or thyroxine is added to water containing tadpoles?

The thyroid gland is composed of $2$ lobes which are located on either side of the $trachea$.

$I.$ Hypothyroidism causes irregularity of the menstrual cycle.
$II.$ Hyperthyroidism adversely affects body physiology.
$III.$ Hypothyroidism causes cretinism.
$IV.$ Hypothyroidism causes goitre.
Which of the above statements are correct?