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Hypothalamic Neuroendocrine Regulation
Published in George H. Gass, Harold M. Kaplan, Handbook of Endocrinology, 2020
The hypophysiotropic system is less concisely organized. Only recently has its complexity been revealed by immunocytochemical techniques. The term describes the disparate system of neurons in the hypophysiotropic area projecting to the external layer of the median eminence where their terminals release their peptidergic, aminergic, and, probably, amino acid contents into the portal vessels to be transported to the adenohypophysis.43 Many of these systems converge on the retrochiasmatic area during their projection to the median eminence and neurohypophysis. The hypothalamic hormones identified and visualized in these neurons are the following: gonadotropin-releasing hormone (GnRH), CRH, TRH, somatostatin (growth hormone release inhibiting factor), GHRH, neurotensin, Met and Leu enkephalin, dynorphin, (β-endorphin, adrenocorticotropic hormone (ACTH), galanin, vasoactive intestinal peptide (VIP), GABA, and dopamine.
Physiology of the Pituitary Gland
Published in John C Watkinson, Raymond W Clarke, Louise Jayne Clark, Adam J Donne, R James A England, Hisham M Mehanna, Gerald William McGarry, Sean Carrie, Basic Sciences Endocrine Surgery Rhinology, 2018
Mária Hérincs, Karen Young, Márta Korbonits
The anterior lobe of the pituitary, the adenohypophysis, comprises approximately 75% of the total pituitary volume. It is functionally linked to the hypothalamus by blood vessels in the pituitary stalk which transmit regulatory hypothalamic hormones to the pituitary. These stimulate or inhibit the synthesis and release of pituitary hormones. The anterior pituitary consists of five major cell types (each secreting specific hormones), organized into cords of cells located around venous sinusoids. The six major hormone products of the anterior pituitary (Table 56.1) are secreted into the sinusoids from which they enter the circulation.
Portal Circulations
Published in Lara Wijayasiri, Kate McCombe, Paul Hatton, David Bogod, The Primary FRCA Structured Oral Examination Study Guide 1, 2017
Lara Wijayasiri, Kate McCombe, Paul Hatton, David Bogod
The anterior pituitary: Synthesis and release of hormones is under the control of the hypothalamus.Hypothalamic hormones either stimulate or inhibit the release of hormones from the anterior pituitary.Hypothalamic hormones form an integral link between the nervous system and the endocrine systems.These hypothalamic hormones reach the anterior pituitary via portal blood vessels – the hypothalamo-hypophyseal portal circulation, which directly connect the two regions.This allows hormones synthesised by the hypothalamic neurones to be transported rapidly and directly to the anterior pituitary, avoiding dilution or destruction in the systemic circulation.These hormones diffuse into capillaries of the primary plexus (a capillary network located at the base of the hypothalamus) and are carried by hypophyseal portal veins (which run on the outside of the infundibulum) into the secondary capillary plexus of the anterior pituitary gland.
A patent review of glutaminyl cyclase inhibitors (2004–present)
Published in Expert Opinion on Therapeutic Patents, 2021
Judite R.M. Coimbra, Jorge A.R. Salvador
QC enzymes process substrates under physiological and pathophysiological conditions (Figure 1). QC activity has been shown to mediate the pE-peptide maturation of neuropeptides and hormones within the secretory pathway before secretion, such as thyrotropin-releasing hormone (TRH), gonadotropin-releasing hormone (GnRH), neurotensin and gastrin, as well as the N-terminal pE formation of chemokine CCL2 (monocyte chemoattractant protein-1, MCP-1), CX3CL1 (fractalkine), collagen and fibronectin [6,11,12]. The hypothalamic hormones GnRH and TRH are essential for the regulation of metabolism and fertility in the hypothalamic-pituitary-thyroid and gonadal axes, respectively. Once GnRH and TRH pro-proteins are cleaved, the N-terminal Gln of the mature proteins become pE under physiological conditions. It has been demonstrated that the activity and stability of these peptides depend on the N-terminal pE residue. In particular, the function of TRH and MCP-1 is strictly dependent on this modification because loss or change of this residue leads to a decrease in receptor interaction and hence biological activity [13,14].
Non-adenomatous pituitary tumours mimicking functioning pituitary adenomas
Published in British Journal of Neurosurgery, 2020
Zize Feng, Zhigang Mao, Zongming Wang, Bing Liao, Yonghong Zhu, Haijun Wang
Pituitary hormone secretion is well known to be regulated by hypothalamic hormones and peripheral factors. As mentioned above, the tumours presumably originated from FSCs of the adenohypophysis, which can regulate the secretion of cytokines and growth factors by some endocrine cells.21 However, the question remains if they can also regulate hypothalamic-releasing hormones when they turn into tumour cells following exposure to some hypophysiotropic hormone-releasing substances. The lack of a general understanding of these substances prevented us from examining them more thoroughly, which may have led to some important information being overlooked in the cases presented here.
Combined acute myeloid leukemia and panhypopituitarism
Published in Baylor University Medical Center Proceedings, 2022
Busara Songtanin, Tsuzumi Kanaoka, Joan Chandra, Sushela Chaidarun
Another explanation is an ischemic or thrombotic effect related to hyperleukocytosis. The resulting hyperviscosity and subsequent disruption of hypophyseal portal capillary flow can impede release of hypothalamic hormones destined for the pituitary. Our patient had MRI findings of an abnormally thickened stalk and lack of “bright spot,” which support the hypothesis of leukemic infiltration. However, as noted in reported cases (Table 1) and according to Muller’s report, brain MRI does not always show changes in the pituitary gland.7