Table 6.2. SERUM CORTICOID LEVELS IN RATS FOLLOWING EXPOSURE TO CONTINUOUS
AND INTERMITTENT (6.5 hr/day) 50-HZ MAGNETIC FIELDS
At 3 GHz, rats exposed to 5-10, µW/cm2, 8 hours/day, had elevated levels of excreted corticoids
after I-3 months of exposure (10). At 60 GHz, 15 minutes/day, rats exhibited depressed levels of serum
corticoids after 2 months (11). In such high-frequency EMF studies it is usually impractical to
continuously expose the animals, because the fields can interfere with norrnal feeding and watering
practices, thereby introducing artifacts. Thus, judging from the Udinstev studies, the intermittent
exposure aspect of high-frequency studies is an additional factor-along with the characteristics of the
EMFs and the physiological state of the organism- that will affect the time course of the corticoid
response.
Changes in the gross weight of the adrenal gland reflect changes in its activity. Demokidova
showed that I hour/day EMF exposure of rats produced changes in adrenal weight that were both time
and frequency dependent (12-14). After 2 weeks, exposure at 3 GHz, the adrenals of the exposed rats
were significantly larger than those of the sham-irradiated group: after 5 months, however, there were
no adrenal-weight differences. At 70 MHz, adrenal weights, in the exposed animals were elevated after
1 week's and 1 month's exposure, but following 3 months' exposure they were depressed. After 8
months' exposure at I5 MHz, adrenal weights were similarly depressed below the corresponding
control weight. There are two reports of EMF-induced histological changes in adrenal tissue (14, 15).
The relative size of the innermost or reticular zone of the adrenal cortex was decreased following 3
months' exposure at 70 GHz (14). Exposure to I 30 gauss, 50 Hz, (4 hours/day) for I month resulted in
changes in the blood vessels in the reticular zone along with some hemorrhage and dystrophic cellular
changes (15). Four months' exposure to 5000 v/m, 50 Hz, produced no histological changes and no
change in gross adrenal weight (7).
The Thyroid
Thyroid activity is regulated by the thyroid-stimulating hormone (TSH) secreted by pituitary.
Elevated TSH levels induce the thyroid to elaborate thyroxine, a hormone which functions in at least 20
enzyme systems; one of its major influences involves the acceleration of protein synthesis. High-
frequency EMFs seem to have a general stimulatory effect on the thyroid. At 70 MHz, I50 v/m, 3
months' exposure resulted in an increase in the height of the follicular epithelium in rats-there was no
change in thyroid weight (14) . At 3 GHz, I 53 ,µW/cm2, an increase in thyroid weight was found after
2 weeks' exposure, but after 5 months' exposure the thyroid weights were normal (12). Following 4
months' exposure to 5000 W/crn~, cellular incorporation of radioactive iodine and serum proteinbound
iodine were increased by 50 and II7%, respectively (16). Electron micrographs revealed enhanced
cellular activity that was manifested by an increased number of cytosomes and an enlarged Golgi
apparatus and endoplasmic reticulum (16).
At 50 Hz thyroid activity was depressed as judged by radioactive iodine uptake (7, 17).
Continuous exposure at 1-5 kv/m depressed thyroid activity after 4 months (7): when the field was
removed thyroid activity returned to normal within 6 weeks. Four months intermittent exposure (2
hr/day) at the same field level did not affect thyroid activity, but depressed activity was observed at 7-
15 kv/m (17). Ossenkopp et al. found that both male and female rats exposed in utero to 0.5 Hz, 0.5-30
gauss, had increased thyroid weights at 105-130 days of age (21). Based on this and several other
physiological and behavioral studies, Persinger has implicated the thyroid as a significant factor in the
ELECTROMAGNETISM & LIFE - 87