Prospective Observational Study of Metabolic Myopathy in Cushing's Syndrome or Pheochromocytoma Patients Undergoing Adrenalectomy

Muscle wasting and weakness is important because it accounts for a large proportion of the disability associated with disease and normal aging. The annual economic cost in the USA alone has been estimated at $1.8 billion.

The investigators have studied muscle wasting associated with chronic and acute illness, finding a marked dissociation between wasting and disease severity. This indicated that epigenetic and genetic factors may contribute to individual susceptibility to wasting. To analyse factors controlling muscle mass, the investigators have developed a novel clinical model of muscle loss. Hence, in patients undergoing aortic surgery, a large insult is imposed on patients with a background of a disease that leads to muscle wasting (reduced cardiac function). As the timing of the insult is known, the investigators can follow muscle wasting longitudinally. Our recent work using this model has characterised novel muscle signalling pathways that mediate muscle breakdown. Specifically, the investigators found that 50% of patients undergoing cardiac surgery lose significant muscle mass (>10% in the "wasters" group) in the 7 days after uncomplicated surgery, which correlated with loss of strength 7-9 Expression of microRNAs (miRNAs) from imprinted loci (C19MC miRNAs and miR-675) in muscle biopsy samples was strongly associated with subsequent muscle wasting and weakness. Furthermore, expression of these miRNA in myoblasts and animal models confirms their effects on muscle and suggests modes of action through transforming growth factor signalling pathways, ribosome assembly and mitochondrial function. Finally, metabolomic analysis of plasma samples from these patients suggested that exposure to higher levels of active intrinsic corticosteroid, a known cause of sarcopenia, was correlated with muscle loss. Acute muscle wasting (ICU acquired weakness) is associated with high levels of corticosteroids, owing to a defect in deactivation, and shock which is countered with high doses of catecholamines. The investigators will measure miR expression, and longitudinal muscle bulk and strength in patients undergoing adrenalectomy at SBH.

Group 1: Cushing's syndrome caused by very elevated levels of corticosteroids, associated with severe wasting.

Group 2: Phaeochromocytoma and paraganglioma (PPGL) caused by very elevated levels of catecholamines, associated with moderate wasting.

Group 3: Conn's syndrome caused by elevated mineralocorticoid, not associated with muscle wasting (Control group) All patients will be assessed at diagnosis, after medical treatment and after completed reversal of the defect after surgery. Various measures of focal and global strength and function will be recorded alongside measures of muscle bulk. A muscle biopsy from the wound site will be taken at surgery.