Clinical science
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1. The distribution of intact parathyroid hormone-(1-84) [PTH-(1-84)] and of its COOH-terminal fragments was determined in human serum by column chromatography. In addition to PTH-(1-84) (peak I), COOH-terminal fragments having molecular weights of approximately 4000-7000 (peak II) and immunoreactive components co-eluting with human PTH-(1-12) (peak III) were observed. 2. ⋯ In chronic renal failure as well as in a group of patients with vitamin D deficiency, pseudohypoparathyroidism and primary hyperparathyroidism and in controls, significant linear relations were found between the serum concentrations of calcium and log (peak II/peak I). Our findings suggest that the conversion of intact PTH-(1-84) into COOH-terminal fragments by the parathyroid glands (resulting in a raised secretion of fragments) and/or in peripheral organs may be directly related to the serum concentration of calcium. However, the degradation of the fragments may also be suppressed in a calcium-dependent manner.