Addison's disease and the regulation of potassium: the role of insulin and aldosterone.

It is proposed that insulin has a cardinal role in the regulation of serum potassium levels in man, which may be of greater importance than the effect of insulin on glucose metabolism. Although the first described action of insulin was on glucose transport, it is a hormone with many functions some of which may operate in a metabolic hierarchy depending on the relative importance of the action required. Insulin also promotes the transport of potassium ions from the extracellular space to the intracellular space and it is suggested that there are occasions where this action may take place at the expense of glucose regulation. In metabolic terms, tight control of serum potassium is of greater importance than precise control of serum glucose, because quite small variations in serum potassium may cause death whereas wide variations in serum glucose may be tolerated. Serum potassium levels generally remain very stable despite large daily variations in potassium intake. It follows that potassium control mechanisms must be of outstanding efficiency as serious disturbances of potassium balance are relatively uncommon. 'Nature makes experiments on Man': shadowy but important physiological mechanisms that may almost be taken for granted in normal health are often brightly illuminated by unusual pathological conditions. This paper describes two remarkable patients who presented with extreme hyperkalaemia. This condition was the result of simultaneous insulin and aldosterone deficiency occurring because of concomitant diabetes and Addison's disease. Other medical conditions with disturbances in aldosterone, insulin and potassium control will be referred to in support of the hypothesis that insulin secretion is central to potassium regulation. This hypothesis explains the secondary disturbances in glucose metabolism that occurs in clinical situations where the primary problem is perturbation of potassium regulation.

The sharpened Romberg test for assessing ataxia in mild acute mountain sickness.

OBJECTIVE: To evaluate the Sharpened Romberg Test (SRT) as a measure of ataxia in subjects with mild acute mountain sickness in order to determine its sensitivity and specificity. METHODS: The SRT was performed in 23 subjects during ascent to 5260 m. RESULTS: The SRT was more often abnormal than the traditional heel-to-toe test, and at the highest altitude it was related to higher median Lake Louise symptom scores with predictive values of 60% sensitivity and 89% specificity. Our evaluation of the SRT appears to agree with similar studies on ataxia showing a lack of correlation between ataxia and symptoms of acute mountain sickness at altitudes below 5260 m. CONCLUSION: The SRT was easy to perform and provided a quantitative assessment of truncal ataxia in the field without the need for specialized equipment.

Serum test for assessment of patients with Bence Jones myeloma.

Bence Jones protein in urine (immunoglobulin free-light-chains) is characteristic of light-chain multiple myeloma. We aimed to compare a quantitative immunoassay for serum free-light-chains with urine tests. Of 224 patients with light-chain myeloma tested at entry to clinical trials, all were correctly identified from serum samples. During monitoring of 82 patients, changes in serum and urine free-light-chains corresponded, but urine became negative for free-light-chains in 26 patients, whereas it remained abnormal in serum in 73 patients. Serum assays could replace Bence Jones protein urine tests for patients with light-chain multiple myeloma.