The table shows hormone concentrations in three people. The normal ranges are given.
Table
| Person | Thyroxine in arbitrary units | TSH in arbitrary units |
|---|---|---|
| P | 5 | 9 |
| Q | 5 | 1 |
| R | 15 | 3 |
| Normal range | 10–20 | 2–4 |
Which person has results most consistent with a thyroid gland that fails to respond to TSH, while the pituitary functions normally?
P, because low thyroxine is accompanied by high TSH.
Q, because low thyroxine is accompanied by low TSH.
R, because normal thyroxine is accompanied by normal TSH.
P, because high TSH shows that thyroxine is high.
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.