Increased basic fibroblast growth factor in plasma from multiple endocrine neoplasia type 1: relation to pituitary tumor.

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant disorder characterized by tumors of the parathyroids, pancreatic islets, and anterior pituitary. We previously reported a basic fibroblast growth factor (bFGF)-like substance in the plasma of subjects with MEN1. In the present study we used a novel sensitive specific 2-site immunoradiometric assay to test for bFGF in plasma. The assay employs immobilized affinity-purified N-terminal-specific anti-bFGF antibodies (antigen capture) and high affinity binding to radioiodinated heparin. bFGF-like immunoreactivity was undetectable (< 0.2 ng/mL) in normal subjects and in most unaffected relatives of MEN1 subjects. We found detectable bFGF ranging from 0.24-1.28 ng/mL in 21 of 50 subjects with MEN1. Seven of 8 MEN1 subjects with untreated pituitary tumors had detectable plasma bFGF-like immunoreactivity. Plasma bFGF-like immunoreactivity decreased after surgery for pituitary tumor in 4 patients and after initiation of bromocryptine therapy in 4 patients. bFGF was increased in the plasma of several subjects with sporadic endocrine disorders, including 3 with untreated or persistent acromegaly. We conclude that pituitary tumor is a possible source of high circulating bFGF immunoreactivity in MEN1 plasma.