One of the following is $NOT$ a thyroid hormone. It is . . . . . . .

Which disease in adults is characterized by the following symptoms: $1.$ Low metabolic rate,$2.$ Increase in body weight,$3.$ Water retention in tissues?

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

Which of the following radioactive isotopes is used to detect thyroid cancer?

Graves' disease is caused due to

$A$ gland $X$ is present over the surface of another gland $Y$. The latter secretes a hormone that controls the metabolism of proteins,fats,and carbohydrates. The $X$ and $Y$ are: