[The circulating forms of human calcitonin].

It is demonstrated for the first time that there are at least two forms of immunoreactive CT in serum: the first has the same physico-chemical properties as synthetic CT whereas the second one has a higher molecular weight than synthetic CT, close to the molecular weight of serum albumin. Such heterogeneity was found in the sera of normal subjects and in the sera of patients suffering from several diseases. Results suggest that the percentages of these two forms vary from one serum to another.