Electromagnetic Fields and Human Endocrine System

Extremely low frequency electromagnetic fields (ELF EMF) are commonly present in daily life all over the world. Moreover, EMF are used in the physiotherapy of many diseases because of their beneficial effects. There is widespread public concern that EMF may have potential consequences for human health. Although experimental animal studies indicate that EMF may influence secretion of some hormones, the data on the effects of EMF on human endocrine system are scarce. Most of the results concentrate on influence of EMF on secretion of melatonin. In this review, the data on the influence of EMF on human endocrine system are briefly presented and discussed.


INTRODUCTION
Extremely low frequency electromagnetic fields (ELF EMF) are commonly present in daily life all over the world. They are associated with the use of electric power applied in residential and occupational environments. Wherever electricity is generated, transmitted, or used, electric and magnetic fields are created due to the presence of motion of electric charges. They are emitted by power lines, electrical panels, transformers, and service wires, but also by such household appliances as televisions, electric blankets, hair driers, etc. [1]. Moreover, electromagnetic fields (EMF) are used in the physiotherapy of many diseases (e.g., low back pain syndrome, migraine and vasomotoric headaches, multiple sclerosis, degenerative processes of the bones and joints, rheumatoid arthritis) because of their beneficial effects (e.g., improvement of soft tissue regeneration processes, vasodilatory action, acceleration of bone adhesion formation, anti-inflammatory and analgesic action) [2,3].
There is widespread public concern that EMF may have potential consequences for human health[1, 4,5], especially associated with increased risk for cancer and childhood leukemia [5].
Additionally some attention has also been paid to other possible health hazards, such as interference with cardiac pacemakers [6], Alzheimer's disease [7], and adverse pregnancy outcome [8].
Although there is still scientific controversy concerning that problem, it seems to be a growing consensus that human health hazard associated with exposure to EMF is either very small or restricted to small subgroups. A Working Group organized by the National Institute of Environmental Health Services concluded in a report published in 1998, on the basis of almost 900 publications, that: "None of the evidence for adverse health effects seen after exposure to ELF EMF achieved a degree of evidence exceeding 'inadequate' (for humans) or 'weak' (for experimental animals)"[1].
Studies on the effects of EMF in humans concentrate mainly on power line frequency fields or fields used in mobile phones. The influence of ELF EMF used in physiotherapy on the endocrine system was rarely examined.
Although experimental animal studies indicate that EMF may influence secretion of some hormones [9,10,11,12,13,14], the data on the effects of EMF on the human endocrine system are scarce. Most of the results concentrate on the influence of EMF on secretion of melatonin. In this review, the data on the influence of EMF on the human endocrine system are briefly presented and discussed.

ELECTROMAGNETIC FIELDS AND PITUITARY -THYROID AXIS
Generally, EMF did not significantly influence hormones secreted by pituitary -thyroid axis [41,43] ( Table 2). However, Woldanska-Okonska and Czernicki [43] observed differences in fT3 and fT4 levels after exposure to EMF of 2.9 mT, 40 Hz in comparison to 25-80 µT, 200 Hz 1 month following 3-weeks application. Moreover, among the studied patients, the authors have found the individuals especially sensitive to EMF in terms of secretion of TSH, fT3, and fT4.

CONCLUDING REMARKS
In general, it seems that EMF exert no or very subtle effects on the endocrine system. Small differences reported in various studies may depend on different characteristics of applied magnetic fields and different experimental paradigm.

ACKNOWLEDGMENTS
The work by the authors and this review were supported by a grant from Medical University of Lodz, No. 503-129-2.