# Explain how thyroxine and negative feedback work together to maintain a stable metabolic rate in the body.

> AQA GCSE Biology (8461) — 4.5.3 Hormonal coordination in humans · Explain · 4 marks

## Mark scheme (4 marks)

1. Thyroxine is produced by the thyroid gland and increases the metabolic rate
2. When thyroxine levels in the blood are too high, this is detected and the thyroid gland is signalled to reduce thyroxine production
3. When thyroxine levels fall too low, the thyroid gland is stimulated to produce more thyroxine
4. This is negative feedback because the change is reversed / the system returns to the optimum / stable level

## Key terms

- [thyroxine](https://www.gradenine.co.uk/glossary/thyroxine)
- [metabolic rate](https://www.gradenine.co.uk/glossary/metabolic-rate)

## Related

- [Revision notes for AQA GCSE Biology (8461)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-thyroxine-and-negative-feedback-01bd0a99) · Published by Druglandscape Ltd.