Marla Ahlgrimm explains that the primary culprit for most of these changes is estrogen. Estrogen is also responsible for the major changes that pubescent girls experience, including pubic hair, breasts, and the beginning of her menstrual cycle. In addition to estrogen’s known necessity to childbearing, it also protects the bone, affects mood, and works to keep cholesterol controlled. Estrogen is also found in tissues throughout the body, including the skin and heart.
Marla Ahlgrimm explains that the primary source of estrogen is the ovaries. This is where eggs are made. Estrogen is also produced by the adrenal gland, a small gland located at the top of each kidney. Marla Ahlgrimm notes that estrogen moves to the bloodstream and impacts every cell in the body. Although estrogen levels change throughout the month, they are highest mid-menstrual cycle and lowest once a woman’s period begins.