A person's thyroid gland secretes thyroxine at an unusually high rate. A doctor plans to give the person a medicine that reduces thyroxine secretion.
Before treatment begins, the concentration of TSH in the person's blood is below normal.
Explain why the person may release and use more energy per unit time than a person whose thyroid secretes thyroxine at a normal rate.
Explain how the unusually high secretion of thyroxine results in the low concentration of TSH.
The medicine lowers thyroxine secretion until the blood thyroxine concentration is normal.
Predict the effect of this treatment on the concentration of TSH.
Give a reason for your answer.
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.