Some life transitions, such as entering puberty, trigger hormonal changes that may alter the stress response.

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Maternal prenatal stress, hormonal changes in mother and developing fetus, and resulting changes in neurodevelopment are also potentially associated.

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And labor, with accompanying pain, fast heartbeat and hormonal changes, "that's the most dangerous and challenging time, " Dr. Franklin says.

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This made Dr. Geske Ursin and her colleagues wonder whether the hormonal changes associated with pregnancy and breast-feeding were somehow the reason.

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These hormonal changes can be disastrous when they strike a young child.

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Diabetes diagnosed during pregnancy, known as gestational diabetes, is influenced by hormonal changes and normal weight gain and usually goes away after the baby is born.

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Their theory is that this variety of receptor might help, in normal circumstances, to keep control over the brain's response to huge hormonal changes during and immediately after pregnancy.

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However the study does tally with several others, some of which have found that hormonal changes brought on by a lack of sleep can lead to an increased appetite.

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Many theories exist as to why some women suffer terribly from morning sickness and others appear to escape unscathed, but a major factor is likely to be the body reacting to hormonal changes.

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She has chosen 51 genes to study, including those involved in the body's responses to stress and infection, in hormonal changes related to pregnancy, and in ways in which the body handles a wide variety of environmental toxins.

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Before I answer your question, let me clarify that while metabolism does drop with age (about 3 percent per decade) due to muscle loss and hormonal changes, it does not drop with exercise, but rather increases due to direct calorie burning during your workouts and indirectly through an increase in muscle mass as a result of your workouts.

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Artificial fat elicits similar biological responses as real fat, including increased salivation, hormonal reactions, and metabolic changes.

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