Human parathyroid hormone: Glandular and secreted molecular species

Purified human parathyroid hormone (hPTH) from urea extracts of parathyroid adenomata (gland-extracted PTH) is immunochemically different from the hPTH in hyperparathyroid serum (serum PTH) and from the hPTH secreted into the medium of cultures of parathyroid adenoma slices (culture medium PTH). However, serum PTH is immunologically indistinguishable from culture medium PTH. Crude urea extracts of parathyroid adenomas are immunologically heterogeneous, and gel filtration studies of medium from scaled-up parathyroid adenoma cultures show that the medium contains at least two and probably three immunologic species of PTH, indicating that it also is immunochemically heterogeneous. The major fraction of culture medium PTH is immunologically similar to serum PTH, with a molecular weight (gel filtration) in the range of 5,000 to 7,000 and an amino acid composition similar to Rasmussen's bovine parathyroid hormone B. The other immunologic species in culture medium have molecular weights in the ranges of 9,000 and 14,000 and are immunologically distinct but more closely resemble gland-extracted hormone. These observations have important bearing on the possible existence of a glandular precursor to secreted PTH and on the great difficulties which have been experienced in the development of useful radioimmunoassays for human parathyroid hormone in serum.