Question

Question 16 In people with Grave’s disease, the immune system produces a large amount of a protein that is so much like TSH (Thyroid stimulating hormone) that it binds to cells of the thyroid gland and acts like TSH. Unlike TSH, the secretion of this protein does not respond to negative feedback.

a) What effect will this abnormal protein have on the function of the thyroid gland?

b) What effect will this abnormal protein have on the release on hormones from the hypothalamus and anterior pituitary gland?

c) If TSH binds to membrane-bound receptors on cells of the thyroid gland will a second messenger system be needed for hormonal action? Explain.

Answer 1

Answer -

a) In Grave’s disease, the immune system produces a large amount of a protein that is so much like TSH (Thyroid-stimulating hormone) that it binds to cells of the thyroid gland and acts like TSH and does not respond to negative feedback. This lead to hyperthyroidism, or overactive thyroid due to lack of negative feedback .

b) The hypothalamus releases thyroid-releasing hormone (TRH), which stimulates the anterior pituitary gland to secrete TSH. Now this TSH stimulates the thyroid gland to release thyroxine. Thyroxine can then exert negative feedback on TSH levels with high levels of thyroxine decreasing TSH and low levels of thyroxine increasing TSH levels from the anterior pituitary. Now due to lack of negative feedback, thyroxine can not suppress the production.

c) When a hormone binds with membrane-bound receptors it itiates a series of events. If normal TSH binds to membrane-bound receptors on cells of the thyroid gland then second messenger system willbe  needed for hormonal action.