GRF Secretion in Man

Abstract

The isolation and characterization of the growth hormone (GH) releasing peptides 1–37 (GRF 37), 1–40 (GRF 40) and 1–44 (GRF 44) have led to the generation of antibodies which have been used for immunocytochemistry techniques and the development of assays based on standard competitive protein binding principles. These procedures are now being used to measure circulating levels of GRF in man in both normal and disease states and to investigate abnormalities associated with the release of this peptide. Recently, GRF 40 and GRF 44, which are immunologically and biochemically identical to GRF of pancreatic origin, have been demonstrated in human hypothalamic extracts (1,2). Immunohistochemical studies in both rats and primates have demonstrated the presence of GRF-positive neurons in the hypothalamus and median eminence (3). Further immunohistochemical studies have also demonstrated the presence of immunoreactive GRF in several pancreatic endocrine tumors (4-6). In a large retrospective study, GRF immunoreactivity was detected in 4/24 pancreatic carcinoids, 1/5 bronchial carcinoids, 2/15 gut carcinoids, 1/2 thymic carcinoids, 2/20 medullary carcinomas of thyroid, 1/12 pheochromocytomas and 5/20 small cell carcinomas of lung (7). In this series, clinical features of acromegaly were present in only 2 of the 4 pancreatic carcinoids and in the single patient with a bronchial carcinoid tumor. These data are concordant with earlier case reports of acromegaly associated with bronchial and foregut carcinoids (8–11).