Adrenomedullin expression in pituitary adenomas and nontumoral adenohypophyses

Abstract

Summary. Adrenomedullin (ADM) is a novel peptide originally identified in extracts of human pheochromocytoma. It is produced by several tissues, including the pituitary gland. The presence of ADM has been immunohistochemically demonstrated in pathologic pituitary glands, but no systematic study of ADM expression in human pituitary adenomas has been reported. Thus, we investigated ADM immunoexpression in 88 various hormone-secreting and clinically nonfunctioning pituitary adenoma types as well as 30 nontumoral adenohypophyses. Furthermore, ADM immunoreactivity was assessed on a 0 to +3 scale in all samples. We found strong immunoreativity for ADM in normal gonadotrophs also expressing FSH and LH whereas in the other adenohypophysial cell types expression of ADM was mild. Results showed that normal adenohypophyses were strongly immunopositive for ADM (2.18±0.11). Our findings demonstrate that ADM expression in the anterior pituitary is diminished in tumors as compared to the normal gland. The physiologic function of ADM is unknown, but it could act as a paracrine or autocrine factor in the adenohypophysis.