12 animals were exposed to 50 Hz sinusoidal magnetic field for 18 weeks (24 h/day) and 12 animals received sham exposure. The fields were then removed and the rats remained in the cages for 12 more weeks before they were sacrificed. Blood samples were taken every six weeks: before applying the field, three times while the rats were under the exposure and two follow-up times after removing the field.
Body and uterine weights were not affected by the field. A significant reduction in ovary weights in exposed rats was observed when compared with sham exposed controls. The reduction in the levels of follicle stimulating hormone and luteinizing hormone was significant after six weeks of exposure. Follicle stimulating hormone levels were affected only on week 6 after exposure while luteinizing hormone remained affected during 12 and 18 weeks. No significant effects were found at 6 and 12 weeks after removing the field. The level of progesterone and estrogen was significantly decreased after 12 weeks of exposure, while no other effects on progesterone level was observed during exposure or after removing the field. The level of estrogen was also signifcantly reduced at 12 weeks after removing the field.
These results suggest possible adverse effect on mammalian fertility and reproduction. The effects of extremely low frequency magnetic fields on sex hormones were shown to be partly reversible.