Cardiac and Skeletal Muscle Energy Metabolism in Abnormal Growth Hormone States

Plain-language summary

Growth hormone (GH) is important for growth in childhood, but also has important effects on a number of tissues throughout life. GH deficiency and GH excess (acromegaly, caused by a pituitary tumour) are both cause serious abnormalities of metabolism and long-standing abnormal GH status causes abnormal heart function. In both cases cardiovascular disease is a leading cause of early (premature) death. In the current study we wish to investigate the energy status of the heart in patients with GH excess and deficiency and compare that with age-matched controls. We will perform a blood test to study metabolic parameters. We will perform measurements before treatment, after normalisation of improvement of GH levels and 2 years after start of treatment. Objectives 1. Determine cardiac and skeletal muscle energy metabolism in patients with GH excess (=acromegaly) or GH deficiency and detect changes after normalisation of GH and IGF-1 levels. (IGF-I is a hormone directly influenced by GH) 2. To correlate muscle energy metabolism parameters to GH and IGF-1 status in the control subjects and in both patient groups 3. Determine the prevalence of coronary artery calcifications in patients with GH excess and GH deficiency and correlate this with their metabolic status 4. To correlate coronary artery calcifications to abdominal obesity. Patients will be identified by Endocrinology physicians involved in the study in outpatients clinics or Endocrine wards and they will receive standard care for their disease. Tests related to endocrine hormone abnormalities will be performed as usual clinical practice. The study will involve three 3-hour visits to the Oxford Research Centre and two 1-hour visits to London Scanning Centre. The visits at the Oxford research centre will include Cardiac and skeletal investigations * Standard cardiac MRI will be used to measure right and left ventricular morphology and global function. * 31P Magnetic Resonance Spectroscopy (MRS) to monitor heart muscle energy levels (by measuring intracellular PCr and ATP in heart muscle). * Heart failure severity (so called 'NYHA status') will be determined from the 6 min walk test. * Peak oxygen uptake will be estimated from a metabolic gas exchange analysis performed during maximal treadmill exercise testing. * Skeletal muscle MR imaging and spectroscopy will be performed at rest and during exercise. * Fasting blood test will be performed, see details in protocol. * Electrocardiogram (ECG) * Epworth Sleepiness Scale questionnaire and 5 point test for sleep apnoea The visits at the London Scanning Centre will include * Electron beam coronary CT (EBCT) to assess coronary disease. The number of coronary disease lesions will be measured in several coronary arteries and values will add up to an overall score. In addition a single picture will be taken at the level of the umbilicus (belly button) to measure fat tissue within the abdomen. Patient selection: Patients will be recruited at St. Bartholomew's Hospital (Dr P. Jenkins and Prof. A. Grossman), King's Hospital (Dr S. Aylwin) and St Thomas's Hospital (Dr P. Carroll) in London, Royal Free Hospital (Prof P. Boloux), the John Radcliffe Hospital Oxford (Prof J. Wass), Addenbrooks Hospital Cambridge (Dr H. Simpson), Sheffield (Dr J. Newell-Price), and Stroke-on-Trent (Prof R. Clayton) from the Endocrine Wards and outpatient clinics. This constitutes a large recruitment base. We estimate that 45 new acromegaly patients and 60-80 new GHD patients per year will be screened. Patients will be selected on the basis of clinical diagnosis of acromegaly or GH deficiency (see details of these in the formal protocol). Patients will be managed according to the clinical protocols of the referring centre. The patients will have a report of their investigation results with their treating physicians. Control subjects will be selected from the general population via advertisements. They will undergo all tests in the Oxford centre once. Expected value of results: These studies will increase our knowledge of the metabolic changes associated with GH excess and GH deficiency, which can lead to increased cardiac morbidity and mortality in both cases. Our studies will help to clarify the mechanism of abnormal cardiac function. The study has been powered to have appropriate number of subjects within a two year period, therefore we anticipate that it will last from start to finish 4 years.

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