A doctor measured the concentrations of TSH and thyroxine in the blood of two patients, X and Y.
The Table shows the results and the normal range for each hormone.
Table
| Hormone | Patient X | Patient Y | Normal range |
|---|---|---|---|
| TSH in arbitrary units | 9.0 | 0.2 | 0.4 to 4.0 |
| thyroxine in arbitrary units | 6 | 30 | 12 to 22 |
Patient X has a thyroid gland that produces too little thyroxine.
Explain why patient X has a high concentration of TSH.
Patient Y has a thyroid gland that produces too much thyroxine.
Explain why patient Y has a low concentration of TSH.
Patient Y has a high metabolic rate.
Suggest why patient Y may lose body mass even when eating a normal diet.
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.