Patients will be recruited through the outpatient clinics at the University Hospitals Bristol, NHS Foundation Trust, Rheumatology Centre. Each patient will give fully informed consent after being given details of the study and a patient information sheet. The research doctor will take the consent 2−5 days after this information has been provided and with the presence of a witness. The study will consist of the collection and analysis of sequential blood samples over a 24 hour period on 2 occasions 2 weeks apart, taking TRT prednisone 7 mg / standard release prednisolone 7 mg for the intervening period. The investigators will aim to recruit 12 patients in each arm. A single blood sample will be taken when the patient comes for a routine review 2 weeks later.