Why is thyroxine considered a hormone and not an enzyme?

On an educational trip to Uttaranchal,Ketki and her friends observe that many local people have swollen necks. Please help Ketki and her friends to find out the solutions to the following questions.
$(a)$ Which probable disease are these people suffering from?
$(b)$ How is it caused?
$(c)$ What effect does this condition have on pregnancy?

Which of the following endocrine glands stores its secretion in the extracellular space before releasing it into the blood?

Iodine is stored in which of the following glands in the body?

If the thyroid gland is completely removed from a tadpole,it will

$A$ pregnant female delivers a baby who suffers from stunted growth,mental retardation,low intelligence quotient,and abnormal skin. This is the result of: