Extrapituitary production of anterior pituitary hormones: an overview

Abstract

Protein hormones from the anterior pituitary gland have well-established endocrine roles in their peripheral target glands. It is, however, now known that these proteins are also produced within many of their target tissues, in which they act as local autocrine or paracrine factors, with physiological and/or pathophysiological significance. This emerging concept is the focus of this brief review.

Autocrine/paracrine roles of extrapituitary growth hormone and prolactin in health and disease: An overview

“…The concentration of prolactin in CSF is similarly independent of hypophysectomy (Barbanel et al, 1986). Since then, prolactin has now been found in many extrapituitary tissues, as first reviewed by Ben Jonathan et al (1996) and more recently by Harvey at al. (2012) and by Marano and Ben-Jonathan (2014).…”

“…The anterior pituitary gland is the main source of GH, prolactin, luteinizing hormone (LH), follicle-stimulating hormone (FSH), thyrotropin (TSH) and adrenocorticotropin (ACTH) found in peripheral circulation, since the concentrations of these hormones decline or are abolished following hypophysectomy (Harvey et al, 2012). The anterior pituitary is not, however, the only site in which the genes for these hormones are expressed.…”

“…The anterior pituitary is not, however, the only site in which the genes for these hormones are expressed. Indeed, the extrapituitary production of all of these hormones has been demonstrated in neural, immune, reproductive and alimentary tissues (Harvey et al, 2012). In most cases the contribution of the extrapituitary sources to the hormone concentrations in plasma is low, although their hypersecretion can mimic pituitary pathologies, such as acromegaly, hyperprolactinemia, hyperthyroidism, hypergonadism and Cushing's syndrome (Harvey et al, 2012).…”

“…These local roles may be of particular importance in early embryonic or fetal development, before the acquisition of their classical endocrine roles, since extrapituitary hormones are produced in early development prior to the ontogeny of the pituitary gland (Harvey et al, 2012). Extrapituitary production of pituitary hormones may also be a cause or consequence of abnormal (tumorous) development and has often been associated with tumor progression.…”

“…GH and prolactin are also produced within many of these target sites, in which they have autocrine or paracrine actions locally (Ben-Jonathan et al, 1996Harvey, 2010;Harvey et al, 2012). These local roles are of both physiological and pathophysiological significance, as demonstrated by blocking their extrapituitary production or local action.…”