An organ $X$ has a large blood supply. It produces a hormone,the lack of which causes a disease known as cretinism. The organ is

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:

Cretinism,mental retardation,low intelligence quotient,abnormal skin,deaf-mutism,etc.,are the results of:

The two lobes of the thyroid gland are connected by a thin flap of connective tissue called the.....

The hormone responsible for metamorphosis in tadpoles is .....

What is Isthmus?