Identification and Characterization of Calcitonin Forms in Plasma and Urine of Normal Subjects and Medullary Carcinoma Patients*

Different immunoreactive calcitonin (CT) forms were identified by a reversed phase high performance liquid chromatography gradient system in plasma and urine of normal subjects. The separated CT components were characterized by chemical and enzymatic methods and found to be identical in normal subjects and medullary thyroid carcinoma patients. Of seven major CT forms we identified monomeric human CT-(1-32), its sulfoxide form, and dimeric CT in plasma. The monomeric, but not the dimeric form, was also detected in urine. A predominant CT component in plasma with a molecular weight of about 12,000 may correspond to a biosynthetic precursor of the hormone.