Because the pituitary's activities are synchronized with the nervous system via intimate
chemical and neuronal pathways in the hypothalamus, any EMF impact involving pituitary function
would be expected to reach beyond ACTH and the classic stress-response system. There is some direct
evidence that other pituitary secretions are affected by EMF's. For example, antldiuretic hormone
(ADH) Is a pitultary secretlon that partlclpates in the regulation of the body's water balance. An
increase in ADH fosters the reabsorption of water by the kidney's distal renal tubules thereby leading to
a reduction in diuresis (flow of urine). Several studies have reported that EMFs increase serum ADH
levels (5, 6) and reduce diuresis (6, 7). In many cases, however, the evidence of EMF impacts
involving the pituitary is indirect and consists of effects on growth, metabolism, the cardiovascular and
hematopoietic systems, and other body functions and systems that are under the influence and control
of the endocrine system. In the remainder of this chapter we describe the EMF studies that involve the
endocrine glands-principally the adrenal and thyroid. In succeeding chapters we present evidence of the
effects of EMFs on other body functions and systems.
The Adrenal Cortex
The adrenal corticoid response to EMF stimulation is highly time-dependent (7). When groups
of rats were exposed to 500, I000, 2000 and 5000 v/m at 50 Hz, the average urine-corticoid level of the
latter two groups changed similarly during the 4-month exposure period (7): approximately the same
maximum value was achieved in both groups and they exhibited increased corticoid levels as compared
to the controls. The Iooo-v/m group, however, exhibited lower corticoid levels for the first 2 months of
the exposure period followed by a rise above the control level during the last half of the exposure
period; at 500 v/m the pattern of corticoid excretion was identical to that of the controls. The biological
response was reversible in the sense that when the hela was removed, the corticoid level returned to
normal within 2 months.
One of the important factors governing the time course of the corticoid level-and hence the
dynamics of the pituitary-adrenal response-is the ratio of the exposure period to the nonexposure
period. This was established by Udinstev who exposed groups of rats to 200 gauss, 50 Hz,
intermittently for 6.5 hours/day, for 1, 3, 5, and 7 days, and, continuously for I and 7 days (9) (Table
6.2). The corticoid level in the continuously exposed rats was significantly greater than in the controls:
following intermittent exposure, however, the corticoid response was considerably different. After 4
days-the total cumulative exposure was 26 hours-it was significantly lower in the exposed rats, and this
trend continued after 5 and 7 days of intermittent exposure.
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