Many people think of the fatty substance cholesterol as a sort of toxin to be completely removed from the body. It is true that too much cholesterol can lead to life-threatening diseases of the heart and blood vessels. At the same time, a certain amount of cholesterol is necessary for life. The relationship of cholesterol to the hormone aldosterone illustrates this point.
Aldosterone Function
Human beings cannot survive without aldosterone. This hormone plays an essential part in the work of the kidneys, which filter the blood, excreting some substances into the urine and keeping others in the body. Aldosterone stimulates the kidneys to retain sodium and thus keep more water in the body, while promoting the excretion of potassium into the urine. In this way aldosterone helps to maintain blood pressure.
Cholesterol Function
Diets with limited cholesterol and other fats are critical to preventing cardiovascular disease. Yet only about 25 percent of cholesterol in the bloodstream comes from eating animal foods. The liver and other cells, especially in the intestines, actually make the other 75 percent. Cholesterol is an essential building block of cell membranes. The body makes steroids, an important class of hormones, and bile acids, which help the gut absorb fats, from molecules of cholesterol.
Aldosterone Biosynthesis
Biosynthesis is the process by which the body makes a particular substance, such as a steroid hormone like aldosterone. Aldosterone is biosynthesized in the cortex, the outer part, of the adrenal glands, which sit on top of each kidney. First the adrenal cortex takes up cholesterol. It then converts the cholesterol into a sequence of four other chemicals and finally into aldosterone, which is then released into the bloodstream.
Feedback Loops
Feedback loops govern the making and release of hormones in the body, including aldosterone. This simply means that the increase or decrease of a particular substance in the body leads to to the increase or decrease in the making and release of a hormone. Obviously the body needs to maintain a certain level of cholesterol to produce enough aldosterone and other steroid hormones. This is almost never a problem except in the case of a rare genetic disease, Smith-Lemli-Opitz syndrome, that disrupts the body's ability to make cholesterol.
Aldosterone Secretion Abnormalities
Most diseases involving too much or too little aldosterone secretion are not caused by too much or too little cholesterol in the body. For example, Addison's disease, which results from too little aldosterone and cortisol, another adrenal hormone, is often caused by autoimmune damage to the adrenal glands. Conn's syndrome, a disorder of too much aldosterone production, most frequently arises from an adrenal gland tumor.
References
- Advances in Physiology Education: Teaching Aldosterone Regulation and Basic Scientific Principles
- American Heart Association: About Cholesterol
- Colorado State University: Endocrine Index: Adrenal Glands: Mineralocorticoids
- Medical Biochemistry Page: Cholesterol and Bile Metabolism
- National Center for Biotechnology Information: Bookshelf: Endocrinology, An Intergrated Approach: Chapter 4-The Adrenal Gland
