Endocrine system diversity

THE DIVERSITY OF THE ENDOCRINE SYSTEM / 437 Table 42-4. General features of hormone classes. 

Much of the material on individual endocrine glands present in the twenty-fifth edition has been replaced with new chapters dealing with the diversity of the endocrine system, with molecular mechanisms of hormone action, and with signal transduction. 

The endocrine system is an anatomically diverse assemblage of organs, united by the common fnnetion of secreting hormones. Organs, with qnite different fnnetions, inclnding the kidney, liver and intestine, also secrete hormones and, in this sense, they too are part of the endocrine system. In a functional sense, the endocrine system also inclndes the blood which transports hormones to their target cells, tissues or organs. 

The most important clinical application of glucocorticoids and their semisynthetic analogs is their anti-inflammatory activity, discovered in 1949 by Hench and co-workers. The profound anti-inflammatory effects of glucocorticoids arise from the combined effects of these steroids on both the cellular and molecular mediators of inflammation these effects are separate from the metabolic effects described above and further indication of the widespread diversity of macromolecules to which steroids can bind. Glucocorticoids suppress inflammation at the cellular level by downregulating the concentration, distribution, and function of leukocytes (white blood cells) that profoundly influence inflammation and response to infection within the body (In this way, steroids help to mediate the overlap between the endocrine systems [chapter 5] and the immune systems [chapter 6]). Glucocorticoids also suppress inflammation at the molecule level by suppressing inflammatory cytokines, chemokines, and other molecular mediators of inflammation. 

There has been considerable concern in recent years over the possible increasing trends for adverse effects on the reproductive capabilities of animals and man. In humans, effects such as decreased sperm count and increased testicular cancer in men and breast cancer in women are of particular concern.71 It has been proposed that a common cause for these diverse observations may be the disruption by certain environmental contaminants of the endocrine system which... 

Granner DK. The diversity of the endocrine system. In Mnrray RK, Graimer DK, Mayes PA, et al. Harper s ninstrated Biochemistry, 26th ed. New York Lange Medical Books/McGraw-HUl, 2003. 

The great diversity and amounts of hormones and regulatory molecules secreted by the GIT influence local and systemic functions. As a consequence, phytochemicals that modulate the endocrine functions of the GIT can alter its characteristics and those of other organ systems. 

In animals, adrenomedullin dilates resistance vessels in the kidney, brain, lung, hind limbs, and mesentery, resulting in a marked, long-lasting hypotension. The hypotension in turn causes reflex increases in heart rate and cardiac output. Adrenomedullin also acts on the kidneys to increase sodium excretion, and exerts several endocrine effects including inhibition of aldosterone and insulin secretion. Finally it acts on the central nervous system to increase sympathetic outflow. These diverse actions of adrenomedullin are mediated both by CGRP receptors and unique adrenomedullin receptors, the properties of which are incompletely defined. The major second messenger for both receptors is cAMP. 

Several lines of evidence indicate that macromolecules of as yet unidentified chemical nature, produced by cancers and released into the systemic circulation, are responsible for the biochemical alterations in the liver and other host organs. In view of the diverse regulatory properties of the many different enzymes that increase or decrease towards their immature level (see Table III), a deficiency or excess in any given endocrine or dietary factor can clearly not explain the phenomenon. Nor has it been possible to implicate reductions in the efficacy of these factors. Subnormal concentration of the nuclear thyroid hormone receptor has been noted in the liver of tumor-bearing animals(24) however, since losses in the T3-inducible catalysts of the same liver occurred at much earlier stages of tumor-bearing,(24) the subnormal receptor concentration could clearly not be the cause of these losses but was probably another, and rather late, reflection of the process of biochemical undifferentiation. 

Walker data set — Walker et al., developed a database that contains a large and diverse collection of known pesticides and industrial chemicals, as well as some food additives and drugs (Walker et al., 2003). The database contains 92,964 Chemical Abstract Service (CAS) Registry numbers of chemicals that will probably have to be evaluated for their potential endocrine disruption. A final data set of 58,391 chemicals was processed by our system after eliminating those chemicals for which structures were not available (Walker et al., 2003) and/or 3D structures could not be generated (Hong et al., 2002). 

Neuropeptides mediate neurotransmission as peptide neurotransmitters and mediate cell-cell communication as peptide hormones for endocrine regulation of target cellular systems. The term neuropeptides refers to this large, diverse class of peptide neurotransmitters and peptide hormones that typically consist of 3 0 residues. More than 100 different neuropeptides exist, and new neuropeptides are yet to be discovered. 

---