A patient has a condition that causes the pituitary gland to release TSH at a fixed rate. The rate of TSH release cannot increase or decrease. The patient's thyroid gland functions normally.
The table shows the results of a blood test.
| Measurement | Patient's result | Normal range |
|---|---|---|
| TSH concentration | 8.0 mU/L | 0.4–4.0 mU/L |
| Thyroxine concentration | 27 pmol/L | 9–23 pmol/L |
Explain why the thyroxine concentration remains above the normal range.
Suggest how the patient's basal metabolic rate is likely to compare with normal.
85 exam-style questions on AQA GCSE Biology 5.3 Hormonal coordination in humans, covering 5.3.1 Human endocrine system, 5.3.2 Control of blood glucose concentration, 5.3.3 Maintaining water and nitrogen balance in the body, 5.3.4 Hormones in human reproduction, 5.3.5 Contraception, 5.3.6 The use of hormones to treat infertility (HT only), and 5.3.7 Negative feedback (HT only). Each one has a worked solution and a mark scheme showing where the marks go.