chapter 2 companion site for basic medical endocrinology, 4th edition author: dr. goodman

Chapter 2Companion site for Basic Medical Endocrinology, 4th Edition

Author: Dr. Goodman

Companion site for Basic Medical Endocrinology, 4th Edition. by Dr. Goodman Copyright © 2009 by Academic Press. All rights reserved.

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Mid-sagittal section of the human pituitary gland and adjacent hypothalamic structures. (From Netter, F.H. (1989) Atlas of Human Anatomy, 2nd Ed. Novartis Summit New Jersey, Icon Learning Systems, LLC, a subsidiary of MediMedia, Inc. Reprinted with permission from Icon Learning Systems, LLC, illustrated by Frank H. Netter, MD. All rights reserved.)

FIGURE 2.1


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Vascular supply of the human pituitary gland. Note the origin of long portal vessels from the primary capillary bed and the origin of short portal vessels from the capillary bed in the lower part of the stalk. Both sets of portal vessels break up into sinusoidal capillaries in the anterior lobe. (From Netter, F.H. (1989) Atlas of Human Anatomy, 2nd Ed. Novartis Summit New Jersey, Icon Learning Systems, LLC, a subsidiary of MediMedia, Inc. Reprinted with permission from Icon Learning Systems, LLC, illustrated by Frank H. Netter, MD. All rights reserved.)

FIGURE 2.2


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The glycoproteins. The three glycoproteins of pituitary origin and the placental HCG all share a common alpha subunit.

FIGURE 2.3


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The growth hormone/prolactin family.

FIGURE 2.4


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Proteolytic processing of pro-opiomelanocortin (POMC). Sections of the intact POMC molecule representing the different final products are shown in the various colors. Sites of cleavage by proconvertase (PC) 1 are indicated by the green arrows, and by PC2 by the red arrows. Some cleavage of -lipotropin in the corticotropes is catalyzed by PC2. Corticotropes express only PC1, but melanotropes in the rudimentary intermediate lobe, neurons, and melanocytes and keratinocytes in the skin express both PC1 and PC2. JP = joining peptide: CLIP = corticotropin-like intermediate lobe peptide. Additional post-translational processing (not shown) includes removal of the carboxyl-terminal amino acid from each of the peptides, glycosylation and phosphorylation of some of the peptide fragments.

FIGURE 2.5


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Development of the principal cell types of the anterior pituitary gland showing some of the critical transcription factors that give rise to each lineage. Corticotropes branch off early and form a separate lineage. Development of each of the other cell types depends on Prop-1. The lactotropes, somatotropes, and thyrotropes are derived from a common precursor until thyrotropes diverge and share a common dependence on GATA-2 with the gonadotropes.

FIGURE 2.6


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Mid-sagittal section of the human hypothalamus and pituitary. The principal nuclei of the hypothalamus are listed within the bracket. (From Netter, F.H. (1989) Atlas of Human Anatomy, 2nd ed. Novartis Summit New Jersey, Icon Learning Systems, LLC, a subsidiary of MediMedia, Inc. Reprinted with permission from Icon Learning Systems, LLC, illustrated by Frank H. Netter, MD. All rights reserved.)

FIGURE 2.7


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Regulation of anterior pituitary hormone secretion. Environmental factors may increase or decrease pituitary activity by increasing or decreasing hypophysiotropic hormone secretion. Pituitary secretions increase the secretion of target gland hormones, which may inhibit further secretion by acting at either the hypothalamus or the pituitary. Pituitary hormones may also inhibit their own secretion by a short feedback loop.

FIGURE 2.8


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Structures of the hormones of the neurohypophysis and their prohormone precursors. Because final processing of the prohormones takes place in the secretory granules, the neurophysins and the glycopeptide fragment are cosecreted with oxytocin or vasopressin, but have no known physiological actions. Amino acid sequences of oxytocin and vasopressin are shown in the single letter code: C = cysteine, Y = tyrosine, F = phenylalanine, I = isoleucine, Q = glutamine, N = asparagine. P = proline, R = arginine, L = leucine, G = glycine.

FIGURE 2.9


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Regulation of oxytocin secretion showing a positive feedback arrangement. Oxytocin stimulates the uterus to contract and causes the cervix to stretch. Increased cervical stretch is sensed by neurons in the cervix and transmitted to the hypothalamus, which signals more oxytocin secretion. Oxytocin secreted in response to suckling forms an open loop feedback system in which positive input is interrupted when the infant is satisfied and stops suckling. Further details are given in Chapter 14.

FIGURE 2.10


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Regulation of vasopressin secretion. Increased blood osmolality or decreased blood volume are sensed in the brain or thorax, respectively, and increase vasopressin secretion. Vasopressin, acting principally on the kidney, produces changes that restore osmolality and volume, thereby shutting down further secretion in a negative feedback arrangement. Further details are given in Chapter 9.

FIGURE 2.11

chapter 2 companion site for basic medical endocrinology, 4th edition author: dr. goodman

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