Peptide hormone precursors, subunits, and fragments as human tumor markers

Hormone-related peptides (HRPs) are more frequently and abundantly produced in ectopic hormone-secreting tumors than in tumors of the respective endocrine glands. Most HRPs may have little functional activity. Therefore, tumors producing even high amounts of HRPs are either clinically silent or produce minor endocrine symptoms. The potential use of HRPs as tumor markers has several limitations. The difference in production and secretion between the tumor tissues and the respective normal endocrine glands is usually only a quantitative one. In cancer patients, different patterns of structural heterogeneity for different forms of hormone precursors and fragments may occur. Marked variation in the production and secretion of HRPs may occur depending on the physiological conditions; in some patients the amounts of HRPs may be about the same as in normal persons. Furthermore, the relative amounts of these substances, either in blood or in tumor tissues, may not be useful for prognosis.