Turnover of plasma proteins.

Studies of plasma protein turnover have been used extensively over the last 20 years both under ex-perimental conditions and in clinical medicine. They have shown that disturbed plasma protein. metab-olism is a very common phenomenon in disease, probably as common as an elevated erythrocyte sedimentation rate. Abnormal Serum Total Protein Concentration Only turnover studies can reveal the mechanism behind an abnormal serum concentration of a given protein. Albumin, the major fraction of serum protein, is usually low when total serum protein is low and hence basic causes of hypoproteinaemia are much the same as those of hypoalbuminaemia: (1) increased catabolism which occurs in a variety of acute conditions such as acute infections, trauma including major surgery and myocardial infarction; (2) abnormal protein loss, which may be due to burns, severe proteinuria or gastrointestinal protein leakage; (3) decreased synthesis which is most often caused by liver disease or malnutrition and/or mal-absorption; (4) haemodilution, which occurs in pregnancy, in some cases of cirrhosis of the liver and in surgical patients who have been overhydrated, especially when renal insufficiency is also present. The causes of hyperproteinaemia are fewer, be-cause it is never due to decreased catabolism or abnormal retention. They include increased synthesis of immunoglobulins, either by normal clones (in chronic inflammatory conditions such as cirrhosis of the liver) or by abnormal clones (myelomatosis), which may produce a significant increase in total serum protein concentration; and haemoconcentra-tion which is seen in severely dehydrated patients (cholera, pyloric stenosis) and increases haemoglobin as well as serum protein concentration. A normal total serum protein concentration does not necessarily imply normal concentration of individual fractions. It may, for instance, mask hypoalbuminaemia with hypergammaglobulinaemia, 'The work was supported by grants from the Danish Medical Re-