Blood samples are collected from a person on four different days. The mean concentration of each hormone is expressed as a percentage of the mean concentration in healthy people.
| Hormone | Mean concentration / % of healthy mean |
|---|---|
| TRH | 185 |
| TSH | 28 |
| thyroxine | 42 |
Explain which gland is most likely failing to respond normally and predict how the person's metabolic rate would compare with the healthy mean.
89 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.