Which hormone increases the reabsorption of water in the kidneys?

The hormone that increases the reabsorption of water in the kidneys is ADH, also known as antidiuretic hormone. ADH is produced in the hypothalamus and stored in the posterior pituitary gland. It plays a crucial role in regulating water balance in the body.

When the body is dehydrated or when blood osmolarity increases, ADH is released into the bloodstream. Once in the kidneys, ADH acts on the collecting ducts, making them more permeable to water. This allows more water to be reabsorbed from the urine back into the bloodstream, thus reducing urine output and helping to concentrate the urine. The overall effect is to conserve water and maintain hydration and blood pressure.

This function of ADH is vital for homeostasis, especially under conditions where the body needs to retain fluids. The other hormones listed do not have a direct role in promoting water reabsorption in the kidneys; rather, they have different functions related to growth, reproduction, and milk production.