Is elevated noradrenaline an aetiological factor in a number of diseases?

1 Here I put forth the hypothesis that noradrenaline (NA), which is a signalling molecule in the brain and sympathetic nervous system (SNS), is an aetiological factor in a number of diseases. 2 In a previous paper (Fitzgerald, Int. J. Cancer, 124, 2009, 257), I examined evidence that elevated NA is a factor in various types of cancer. Here I extend the argument to several other diseases, including diabetes mellitus, open-angle glaucoma, osteoarthritis and rheumatoid arthritis and asthma. 3 The principal hypothesis is that, largely as a result of genetics, elevated noradrenergic tone in the SNS predisposes a large number of individuals to a broad range of diseases. 4 For each of the above five diseases, I briefly examine the following four lines of evidence to assess the hypothesis: i) whether pharmacological studies in rodents that manipulate NA levels or receptors affect these diseases; ii) whether pharmacological manipulation of NA in humans affects these diseases; iii) whether bipolar disorder, excessive body weight, and hypertension, which may all three involve elevated NA, tend to be comorbid with these diseases and iv) whether psychological stressors tend to cause or exacerbate these conditions, since psychological stress is associated with increased release of NA. 5 The four lines of evidence tend to support the hypothesis.