Some entomologists speculate that the proliferation of outdoor lights has contributed to the decline of numerous saturniid moth species in the northeastern United States. Visual orientation is just one sense disrupted by artificial light, though it probably isn't the only one, says Mere-dith West, an Indiana University professor specializing in avian development. Lighting is a powerful stimulus on behavior. If there's enough of it, it can make them act in ways they wouldn't normally. Adult female sea turtles will not emerge from the water to nest and lay eggs on beaches that are bathed in artificial light.
Hormones regulate growth and immune functions.
But they're not produced all the time. If they don't shut down, you overload the body. It can't get rid of them. Hormones are toxic in the wrong amounts. Indeed, a 1998 study at the Mary Imogene Bassett Research Institute in Cooperstown, New York, found that cancerous liver cells in lab rats grew rapidly when they were constantly exposed to light.