Thyroxin was isolated by

$A$ toxic substance present in food prevents the synthesis of thyroxine. As a result,which of the following will occur?

Metamorphosis in frogs is accelerated by $.....$.

Which of the following glands is associated with the consumption of iodized salt?

$I.$ Regulation of $BMR$
$II.$ Supports the process of $RBC$ formation
$III.$ Controls the metabolism of carbohydrates,proteins and fat
$IV.$ Maintenance of water and electrolyte balance
$V.$ Secretion of $TCT$ hormone
Functions written above belong to which of the following glands?

Assertion: The thyroid gland is composed of follicles and stromal tissue.
Reason: Iodine is essential for the normal rate of hormone synthesis in the thyroid.