Examination of the melatonin hypothesis in women exposed at night to EMF or bright light.

Abstract

It has been hypothesized that the increased incidence of breast cancer in industrial societies is related to greater exposure to power-frequency electric and magnetic fields (EMF) and/or the presence of high levels of light at night (LAN). EMF and LAN are said to reduce circulating levels of the hormone melatonin which, in turn, allows estrogen levels to rise and stimulate the turnover of breast epithelial stem cells and increase the risk for malignant transformation. Three laboratory-based studies, in which a total of 53 healthy young women were exposed at night to EMF or to LAN under controlled exposure conditions, were performed to determine whether such exposures reduce melatonin and are associated with further alterations in estrogen. All-night exposure to industrial-strength magnetic fields (60 Hz, 28.3 microT) had no effect on the blood levels of melatonin or estradiol. In contrast, nocturnal melatonin levels were profoundly suppressed, and the time of peak concentration was significantly delayed in women exposed to LAN, regardless of whether they were in the follicular or luteal phase of the menstrual cycle. These changes, however, were not associated with alterations in point-for-point matching measures of estradiol. Women who chronically secrete high or low amounts of melatonin each night (area-under-curve range: 86-1,296 pg/mL) also did not differ in their blood levels of estradiol. Taken together, these results are consistent with a growing body of evidence which generally suggests that environmental EMF exposure has little or no effect on the parameters measured in this report.

Rotating nightshift work and the risk of endometriosis in premenopausal women

“…28 Rotating night work may increase estrogen levels by lowering melatonin levels. 29, 30 Experimental studies corroborate this notion, and several studies lend direct 31, 32 and indirect evidence 33, 34 in support of an inverse association between melatonin and estrogen levels. Melatonin also interferes with the local synthesis of estrogens by regulating the activity of aromatases, the enzymes controlling the conversion from androgenic precursors to estrogens, thus behaving as a selective estrogen enzyme modulator or aromatase inhibitor.…”

Melatonin: Another avenue for treating osteoporosis?

“…13,14 In mammals, it is mainly secreted by the pineal gland during darkness, 15 and exposure to light at night may decrease plasma melatonin levels. 16 Apart from the pineal gland, studies have suggested that melatonin may be synthesized locally in the bone marrow as well as in many other tissues. 17,18 Melatonin synthesized in the bone marrow can accumulate at concentrations twice that of nocturnal blood levels, 17,19,20 which may produce strong local effects on bone.…”

Nocturnal Melatonin Suppression by Adolescents and Adults for Different Levels, Spectra, and Durations of Light Exposure

“…Inconsistent exposure to light and dark, such as that experienced during shift work and rapid trans-meridian travel, disrupts entrainment and desynchronizes the internal circadian pacemaker with local sunrise and sunset (Folkard et al, 1978; Panda, 2018; Patkai et al, 1977). Failure to readapt to the local solar cycle results in an altered phase relationship between the circadian system and the sleep-wake cycle (Graham et al, 2001; Panda, 2018; Travlos et al, 2001; Zeitzer et al, 2000), which can be detrimental to sleep quantity, sleep quality, and health.…”