Which hormone increase is mostly responsible for edema in women taking oral contraceptives?

The increase in estrogen is primarily responsible for the edema often experienced by women taking oral contraceptives. Estrogen plays a significant role in the body's fluid balance, as it can promote the retention of sodium and water. When women take oral contraceptives, which typically contain synthetic forms of estrogen, this can lead to an increase in plasma volume as the body holds onto more fluid, resulting in edema or swelling, particularly in areas like the legs and feet.

In addition, estrogen receptors are present in various tissues, including the kidneys, where estrogen influences sodium reabsorption, thereby contributing to fluid retention. This mechanism is particularly relevant in the context of hormonal contraceptives, where the designed pharmacological effects of the hormones can lead to side effects like edema due to their action on fluid dynamics within the body. Understanding this relationship is essential for recognizing the physiological outcomes of hormone therapy in women's health.