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

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

Which of the following is the largest endocrine gland?

What is the effect of $Thyroxine$ on the metabolic rate?

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R)$.
Assertion $(A):$ During pregnancy,the level of thyroxine is increased in the maternal blood.
Reason $(R):$ Pregnancy is characterised by metabolic changes in the mother.
In the light of the above statements,choose the most appropriate answer from the options given below:

Goitrogenic substances present in food,which interfere with the secretion of thyroxine,induce the development of: