The melatonin hypothesis: a matter of method. (Correspondence).In their paper in EHP EHP abbr. 1. effective horsepower 2. electric horsepower , Graham et al. (1) addressed the effects of electromagnetic fields (EMF emf: see electromotive force. (1) (ElectroMagnetic Field) See electromagnetic radiation. (2) (Enhanced MetaFile) See Windows metafile. ) and light at night (LAN (Local Area Network) A communications network that serves users within a confined geographical area. The "clients" are the user's workstations typically running Windows, although Mac and Linux clients are also used. ) on hormonal regulation, particularly of melatonin melatonin: see pineal gland. melatonin Hormone secreted by the pineal gland of most vertebrates. It appears to be important in regulating sleeping cycles; more is produced at night, and test subjects injected with it become sleepy. and estradiol estradiol /es·tra·di·ol/ (es?trah-di´ol) (es-tra´de-ol) the most potent estrogen in humans; pharmacologically, it is often used in the form of its esters (e.g., e. cypionate, e. . The study provides evidence for the predicted role of exposure to LAN on melatonin levels, which marks the credibility of the setting. However, I am concerned that the relationship between breast cancer and EMF and LAN has been reduced to the mechanistic level of estradiol concentrations, ignoring the importance of the two major factors associated with breast cancer risk: a) prolactin prolactin /pro·lac·tin/ (-lak´tin) a hormone of the anterior pituitary that stimulates and sustains lactation in postpartum mammals, and shows luteotropic activity in certain mammals. pro·lac·tin n. levels as a consequence of hypothalamus-pituitary regulation, which act as stimulants Stimulants A class of drugs, including Ritalin, used to treat people with autism. They may make children calmer and better able to concentrate, but they also may limit growth or have other side effects. Mentioned in: Autism for proliferation of the tissue of origin, increasing chances of mutation; and b) depressiveness as a consequence of low melatonin levels, which are related to lack of sleep. In addition, insomnia at night leads to leaving lights turned on for reading or other activities instead of remaining in the dark, when melatonin is best synthesized; this lack of darkness decreases melatonin synthesis and thus increases the incidence and degree of effects of depression and depressiveness. In addition, women in an experimental situation do not react the same way as stressed, exhausted, unhappy, or desperate women in daily life who are not stimulated by the setting of an experiment that increases attention and functions otherwise more likely down-regulated than not. The influence of electricity on the ubiquitous availability of light as an important stimulus, which aids against depressiveness --with and without insomnia--has been described by Davis et al. (2). For the time being the LAN theory has not lost its value, but it seems not to be open for experimental approaches such as the one published by Graham et al. (1). Rainer Frentzel-Beyme Bremen Institute for Prevention Research and Social Medicine Bremen, Germany E-mail: beyme@bips.uni-bremen.de REFERENCES AND NOTES (1.) Graham C, Cook MR, Gerkovich MM, Sastre A. Examination of the melatonin hypothesis in women exposed at night to EMF or bright light. Environ Health Perspect 109:501-507 (2001). (2.) Davis S, Mirick DK, Stevens RG. Night shift work, light at night, and risk of breast cancer. J Natl Cancer Inst 93:1557-1562 (2001). |
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