The mineral element whose deficiency causes goiter in humans 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:

$A$ toxic agent present in food which interferes with thyroxine synthesis leads to the development of:

What is caused by prolonged disturbance in the secretion of hormones from the thyroid gland?

Grave's disease is caused by the hypersecretion of thyroid hormone and is associated with the

Hyperthyroidism causes which of the following diseases?