Which of the following disorders is related to the thyroid gland?

Tadpoles of a frog can be made to grow into giant-sized tadpoles if they are:

Read the given statements $:$
$(A)$ Hypothyroidism during pregnancy causes defective development and maturation of the growing baby.
$(B)$ Thyroxine does not require a secondary messenger.
$(C)$ Thyroxine plays a major role in the regulation of Basal Metabolic Rate $(BMR)$.
$(D)$ Hypersecretion of thyroxine could cause immunodeficiency.
How many of the above statements are correct?

The hormone that decreases the level of calcium in the blood is -

Graves' disease is caused by . . . . . . .

$A$ pregnant woman delivers a child who suffers from stunted growth,mental retardation,low intelligence quotient $(IQ)$,and abnormal skin. This condition is likely due to: