Specialized cells in the kidney, which form the juxtaglomerular apparatus, are very sensitive to changes in blood pressure - well placed for this function by being wrapped around arterioles. The amount of aldosterone produced is controlled by other substances, including a protein from the kidney known as renin. Aldosterone,īy acting on the kidneys, controls the salt content of the body - by which means it also indirectly controls the blood pressure. The cells which make up all of these regions are full of lipid droplets containing cholesterol, which can be converted into the steroid hormones. The first of these regions produces the steroid aldosterone, while another steroid hormone, cortisol, is produced by the other two regions. Is known now to have three distinct regions: the zona glomerulosa, zone fasciculata, and zona reticularis. Fifty years later, a Guy's Hospital physician, Thomas Addison, showed that the adrenal glands were necessary for life, by identifying them as the site of damage in a previously mysterious and ultimately fatal illness, which became known as Addison's disease.

Their presence was recognized as early as the late sixteenth century, but it was not until 1805 that Cuvier reported that the adrenal was made up of two regions, the cortex on the outside and an inner medulla. They are pyramidal in shape and weigh about 4 g each. Adrenal glands There are two adrenal glands, one sitting on top of each of the kidneys.

Renal glands produce