Before a temporary compound is given, the concentrations of TRH, TSH and thyroxine in a person’s blood are normal.
The compound prevents the hypothalamus and pituitary gland from responding to thyroxine. The thyroid gland continues to respond normally to TSH.
Which change is expected while the compound is active?
The concentrations of both TRH and TSH increase above their starting values.
The concentrations of both TRH and TSH stay at their starting values.
The concentration of TSH increases, but TRH stays at its starting value.
The concentration of TRH increases, but TSH stays at its starting value.
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.