Hormones/hormone system

Develop biomarkers of endocrine disruption. F iirther evidence of endocrine disruption is required in addition to population parameters. Biochemical and histopathological biomarkers are required to identify which hormone systems are affected. 

Mechanistic studies to identify how endocrine disrupting chemicals interact with hormone systems are required. Although population effects coupled with biomarkers of exposure are strongly suggestive of endocrine disruption, the effect could be secondary to metabolic toxicity. Establishing mechanisms may avoid the need to make decisions on a weight of evidence approach alone. 

CRH (Corticotropin releasing hormone) is expressed in the nucleus paraventricularis of the hypothalamus and drives the stress hormone system by activating synthesis and release of corticotropin at the pituitary and in turn corticosteroid from the adrenal cortex. CRH is also expressed at many other brain locations not involved in neuroendocrine regulation, e.g. the prefrontal cortex and the amygdala. Preclinical studies have shown that CRH also coordinates the behavioral adaptation to stress (e.g. anxiety, loss of appetite, decreased sleepiness, autonomic changes, loss of libido). 

Brouwer, A., Morse, D.C., and Lans, M.C. et al. (1998). Interactions of persistent enviromnen-tal organohalogens with the thyroid hormone system Mechanisms and possible conse-qnences for animal and hnman health. Toxicology and Industrial Health 14, 59-84. 

The objective of these studies is to find a neurochemical marker for depression. For obvious reasons, the majority has looked for changes that might affect monoamine function and so the following sections concentrate on these neurotransmitters. (Evidence suggesting that a dysfunction of the gluocorticoid hormonal system could be involved is discussed later.) Most techniques compare depressed and non-depressed (control) subjects and measure ... 

Separate lines of research have implicated either the noradrenergic, serotonergic or the FIFA axis in depression, and there is more evidence, not covered here, that other neuroendocrine systems are involved as well. Yet, all this effort has so far failed to identify disruption of any single transmitter or hormone system as the sole culprit. This points to disruption of the interactions between these different systems as the cause of the problem. 

Renin-angiotensin-aldosterone system (RAAS) The hormonal system controlled mainly by the kidneys and adrenal glands that regulates blood pressure, blood volume, and electrolyte balance. 

So far, we have reviewed the various ways in which complex dose-response curves in intact-tissue bioassays can be the result, the pharmacological resultant, of two or more interacting activities. Now, if all that these bioassays achieved was to blur and obscure the underlying activities, they would have to give way to the newer, analytically simpler assays based on chemistry and biochemistry. However, the beauty of intact-tissue bioassays is that they are analytically tractable by using families of dose-response curves and appropriate mathematical models, the complexity of intact hormone-receptor systems can, indeed, be interpreted. Bioassay allows them to be studied as systems in ways denied to simple biochemical assays. 

HCH also penetrates the placenta barrier [A96, A101]. Complications during pregnancy occurred 1.5 times more frequently in the 213 women whose blood contained HCH than in the 89 women with no signs of this insecticide (78.3% and 58.4% respectively). It is especially significant that twice as many women with HCH in their blood spontaneously miscarried during the first trimester as those without HCH (7.5% and 3.4% respectively). Causal factors included disruptions in prenatal fetal development, and disruptions in women s hormonal systems under the effect of HCH [A96]. Postpartum complications in women who had HCH in their blood were 2.5... 

Thus, this is a global phenomenon of fundamental importance for life on Earth many pesticides and/or their transformation products may substitute their activity for the hormonal system. Many earlier known examples of pesticide activity take on a dire new side in light of these views. Let us provide some illustrations ... 

Affects neural and hormonal systems that control activity and metabolic rates in fish... 

The development of new tests and bioassays is likely to lengthen the list of endocrine disrupters. Recent research on hormonal disruption has not only investigated estrogens and androgens as agonists and antagonists but also considered the development of the individual and the presence of compounds that interfere in other hormonal systems, such as the thyroid system. 

In an earlier chapter we have noted that wide variability of endocrine patterns exists. It would therefore be expected that hormone preparations and drugs known to affect hormone systems would show corresponding variability. 

Certain antibiotics such as the tetracyclines, streptomycin, neomycin and kanamycin can cripple the tubules if taken in excessive amounts. Toxic damage to the kidneys can affect not only their filtration functions, but can alter the organs control over blood levels of certain critical molecules. A complex biochemical-hormonal system controlling blood pressure and volume, for example, is regulated by the kidneys, so that chronic kidney damage can inflict damage on the... 

Substitution, rather than risk management is therefore essential. Chemicals identified as of very high concern, e.g. carcinogens, reproductive toxins, those that persist and bioaccumulate in the environment and affect the hormone system, should be targeted for substitution based on their intrinsic hazards. 

Let us share an example. The body s hormone system is called the endocrine system. Endocrine comes from a Greek prefix that means within (endo-) and a Greek root word that means separate (krineiri). This makes sense when you realize that hormones are substances that carry instructions between separate organs within your body. By adding the suffix -ologist (which means one who studies) to... 

The G-proteins are a family of guanine nucleotide (GTP or GDP) binding proteins that are a component of several hundred hormone-effector systems or hgand-binding... 

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