A person with low thyroxine is given TSH. Their blood thyroxine concentration then rises into the normal range.
Which conclusion can be drawn from this response?
The pituitary responds normally, so the original fault is located elsewhere.
The thyroid can respond, but the original fault is not located.
The thyroid cannot respond, so the original fault is located there.
The hypothalamus cannot respond, so the original fault is located there.
42 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.