Question

The thyroid gland secretes thyroxine (T₄) and triiodothyronine (T₃), together known as thyroid hormone. The secretion of thyroid hormone is regulated by thyrotropin – releasing hormone (TRH) and thyroid – stimulating hormone (TSH) as schematically represented below:

One of the actions of thyroid hormone is to increase the basal metabolic rate (BMR) of a person. A person who has suddenly gained weight and has a swollen neck goes to a doctor. The person also feels tired and mentally dull. Clinical analysis shows that the person has low levels of T₄. The doctor feels that either the pituitary or the thyroid is non-functional. In order to identify the impaired organ the person is given TSH simulation. Which one of the following observations and the conclusions made is correct? 

(A) If there is no change in the T₄ levels, it indicates problem of the pituitary. 

(B) If it leads to increase in the T₄ levels, it indicates problems of the pituitary. 

(C) If it leads to increase in the T₄ levels, it indicates problem of the thyroid. 

(D) If it leads further decrease in the T₄ levels, it indicates problems of the thyroid.

Answer 1

Correct option: (B) If it leads to increase in the T₄ levels, it indicates problems of the pituitary.

Explanation:

The correct conclusion is [B] i.e., problem in pituitary is indicated if there is increase in the T₄ level.