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MRI and histology of lymphocytic hypophysitis. The MRI appearances may be mistaken for a non-functioning adenoma; however, there are distinctive features, including homogeneous enhancement with extension posteriorly and rostrally via the infundibulum (‘infundibulohypophysitis’). There is a dense, destructive lymphocytic infiltrate, leaving islands of residual anterior gland (eosinophilic cells, top right) that in this instance are lactotrophs (bottom left; serial section to top right). The lymphocytes are predominantly T-cells (CD3-positive, bottom left).

Signaling molecules and transcription factors involved in the development of the mouse anterior pituitary from Rathke’s pouch. In the anterior lobe somatotrophs, lactotrophs and caudally-placed thyrotrophs derive from a common lineage, determined by Prop-1 and Pit-1. Independent lineages are observed for a rostrally-placed group of thyrotrophs, corticotrophs, gonadotrophs and intermediate lobe melanotrophs. All cell types are committed to a specific lineage through activation of Notch signalling at the placodal stage. (Adapted from Cohen and Radovick, Endocrine Reviews 23: 431-442, 2002; Zhu X, Gleiberman AS, Rosenfeld MG, Physiol Rev 87: 933-963, 2007; Zhu X, Wang J, Ju B-G, Rosenfeld MG, Curr Op Cell Biol 19: 605-611, 2007).

Development and function of the murine pituitary-hypothalamic axis. Rostral to the presumptive hypothalamus, pituitary development is initiated with the appearance of the hypophyseal placode at 8.5 dpc in the mouse. At 9.5 dpc, the placode invaginates to become the Rathke’s pouch (RP). Within the diencephalon, the infundibulum evaginates towards RP by 10.5 dpc. It will give rise to the median eminence (ME), the pituitary stalk and the posterior lobe, whereas the anterior and intermediate lobes originate from RP. Gradually, hypothalamic neurons forming the different nuclei differentiate. Postnatally, the hypothalamus centralizes peripheral information and controls, through release of hypophysiotropic hormones, pituitary endocrine secretions. Hypothalamic peptide hormones can reach the gland directly, such as oxytocin and vasopressin secreted directly in the posterior lobe, or via the hypophyseal portal system. Hypothalamic neuropeptides (GnRH, gonadotrophin releasing hormone, GHRH GH releasing hormone, TRH TSH releasing hormone, CRH corticotropin releasing hormone and the inhibitory SST, somatostatin) are secreted at the ME and collected by capillaries. Anterior pituitary endocrine cells comprise lactotrophs (producing prolactin, Prl), gonadotrophs (producing luteinizing hormone, LH, and follicle stimulating hormone, FSH), thyrotrophs (producing thyroid stimulating hormone, TSH), corticotrophs (producing adenocorticotropic hormone, ACTH, proteolytically cleaved from proopiomelanocortin, POMC) and somatotrophs (producing growth hormone, GH). Adapted from Rizzoti (2015)