The determination of the primary structure of bovine parathyroid hormone (PTH) has enabled us to carry out the synthesis of the first N-terminal 34 amino acids of the molecule. This synthetic fragment has both phosphaturic and hypercalcemic activity, confirming that the biologic actions of PTH are expressed by a short sequence of the "native" 84 amino acid sequence. Serum immunoreactive PTH of patients with surgically proved parathyroid adenomas decreases with induced hypercalcemia and increases in response to hypocalcemia caused by EDTA infusions. These findings challenge the concept of parathyroid adenoma autonomy. Further studies of selective venous catheterization and immunoassay of serum samples obtained from various sites have not been as successful in the localization of parathyroid lesions as originally reported, but newer technics designed to obtain blood from the thyroid venous effluent show promise. Evidence is presented which confirms the concept of immunochemical heterogeneity of PTH in human serum.
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