The Intermediate Lobe of the Pituitary Gland: Introduction and Background

Abstract

Research from a number of laboratories using a variety of systems has shown that cells from the anterior and intermediate lobes of the pituitary gland, from hypothalamic neurons and from the placenta produce a glycoprotein with the full sequences of corticotropin, β-lipotropin and γ-melanotropin. These peptides in turn contain the sequences of α- and β-melanotropin, CLIP, γ-lipotropin, α-, β- and γ-endorphins and methionine-enkephalin. The precursor molecule, here called protropin, is processed by the four types of cell to give rise to different ratios of corticotropin, CLIP, ß- and γ-lipotropin, α-, β- and γ-endorphins and α-, β- and γ-melanotropins. The physiological roles of these peptides in neurotransmission, pre- and postnatal endocrinology, mental disorders and neoplasia are only now being established.