Before treatment, a person has normal concentrations of TRH, TSH and thyroxine in the blood and a normal metabolic rate. A drug then prevents most body cells from responding to thyroxine. The drug does not affect hormone transport or the responses of the hypothalamus, pituitary gland and thyroid gland.
Which set of changes is most likely after treatment begins?
Metabolic rate remains normal; secretion of TRH and TSH increases; secretion of thyroxine increases.
Metabolic rate remains normal; secretion of TRH and TSH remains near normal; secretion of thyroxine remains near normal.
Metabolic rate decreases; secretion of TRH and TSH remains near normal; secretion of thyroxine remains near normal.
Metabolic rate decreases; secretion of TRH and TSH increases; secretion of thyroxine increases.
89 exam-style questions on Edexcel GCSE Biology 7.1 Hormones and coordination, covering 7.1.1 Endocrine glands and hormone transport, 7.1.2 Adrenalin and fight or flight, and 7.1.3 Thyroxine and negative feedback. Each one has a worked solution and a mark scheme showing where the marks go.