Biologic Markers in Reproductive Toxicology (1989) / Chapter Skim
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Executive Summary
Executive Summary
Pages 1-14
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Despite the substantial expenditures that have been made on the study of basic reproductive and neurodevelopmental processes, knowledge of these processes and their relationship to environmental exposures remains disappointing. However, it is clear that the situation can be improved if science can identify biologic markers of the various steps in the processes.
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A biologic marker of effect is a measurBIOLOGIC MARKERS able biochemical, physiologic, or other alteration within an organism that, depending on magnitude, can be recognized as an established or potential health impairment or disease. A biologic marker of susceptibility is an indicator of an inherent or acquired limitation of an organism's ability to respond to the challenge of exposure to a specific xenobiotic substance.
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An effect is defined as an actual health impairment or recognized disease, an early precursor of a disease process that indicates a potential for impairment of health, or an event peripheral to any disease process but correlated with it and thus predictive of development of impaired health. A biologic marker of an effect or response, then, can be any change that is qualitatively or quantitatively predictive of health impairment or potential impairment resulting from exposure.
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BIOLOGIC MARKERS ASSOCIATED WITH REPRODUCTIVE AND NEURODEVELOPMENTAL TOXICOLOGY From the outset, the subcommittee grappled with the knowledge that the processes under its consideration are complex and normal, and therefore, markers of functioning might well provide the only markers for study. (In contrast, a study of markers of disease would seek to identify signals of adverse health or pathophysiology.)
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Therefore, in applying the oversight committee's definitions of biologic markers, the subcommittee described biologic markers of reproductive function and neurodevelopment in general, and classified them according to their immediate and potential utility in environmental health research: · Biologic markers that could be recommended today for assessment of an exposure and reproductive or developmental response to that exposure. · Biologic markers found promising in laboratory studies that could be recommended for further research aimed at use in clinical and epidemiologic studies.
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BIOLOGIC MARKERS ASSOCIATED WITH MALE REPRODUCTION Information on the frequency of naturally occurring reproductive disorders in the human male and reproductive abnormalities induced by toxic chemicals is sparse. Reproductive health outcomes of two major classes are of concern when human males are exposed to toxic chemicals: pathophysiologic changes that might be associated with alterations in fertility and genetic damage that will be conveyed to future generations.
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Variations in markers must be correlated with doses of specific toxicants and with health outcomes, mechanisms of toxicity must be elucidated, and strategies for risk assessment must be developed. BIOLOGIC MARKERS ASSOCIATED WITH FEMALE REPRODUCTION Information on female reproductive toxicology is even more sparse than that on the male, because of differences in gametogenesis and accessibility of germinal cells and because of the cyclic nature of female reproductive function.
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A systematic assessment might identify relevant animal models for different aspects of the female reproductive process that could be simultaneously studied to evaluate environmental health effects. Germ Cell Damage · Use of new reproductive technologies could provide human materials for examining relationships among oocyte cytogenetics and follicular fluid, serum, and tissue concentrations of pollutants.
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. BIOLOGIC MARKERS ASSOCIATED WITH PREGNANCY Identifying biologic markers of toxic exposures that take place during pregnancy is a multidisciplinary challenge that requires integration of basic and clinical sciences.
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Thus, important biologic markers related to pregnancy have not been linked with exposures to specific xenobiotic agents. The only biologic marker that has diagnostic utility after exposure to a xenobiotic agent is the concentration of alpha-fetoprotein in maternal serum and amniotic fluid after exposure to the drug valproate, for which increased concentration of alpha-fetoprotein is evidence of spine bifida in the fetus resulting from the exposure.
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, effects of in utero exposure noted later in life might be due either to persistence of the xenobiotic or to effects secondary to physiologic changes that occur during earlier critical periods of development. Such considerations have important implications for potential therapeutic interventions designed to alter xenobiotic clearance or otherwise modify toxic outcome.
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· Relationships among minor physical abnormalities, toxicant exposure, and behavioral effects should be established. GENERAL RECOMMENDATIONS AND CONCLUSIONS Assessment of reproductive and developmental health is a task that cuts across several scientific disciplines and international boundaries.
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· Identify populations at high risk for reproductive or developmental health impairment (perhaps populations exposed to drugs with reproductive or developmental toxicity, aging populations, or offspring of women treated with specific drugs during pregnancy) , to serve as test subjects for the initial assessment and validation of biologic markers.
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Few areas have changed in medicine as rapidly as those that are the subject of this report. The problems of reproductive and developmental toxicology remain complex, because advances in our understanding of toxic chemicals have not kept pace with the introduction of new materials BIOLOGIC MARS into the environment.
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