Aldosterone is basically a steroid hormone belonging to the mineralocorticoid family and it is made by the zona glomerulosa (an external part) of the adrenal cortex within the adrenal gland. Aldosterone is extremely vital for the survival of humans, as this hormone is accountable for maintaining the usual salt volumes in the human body; holding the body fluids; as well as sustaining the normal blood pressure.

When this hormone is produced in excessive amounts, it may result in the body retaining sodium, hypertension (high blood pressure), abnormal heart rhythms, and may even possibly lead to paralysis. Aldosterone affects the kidneys directly which lessens the rate of emission of sodium by the body and, at the same time, enhances pace of excretion of potassium ions. This hormone also facilitates the body in controlling the electrolyte balance by its actions on the mineralocorticoid receptor (MR). In addition, it also minimizes sodium (Na+) ion secretion and, hence, the secretion of water and also encourages potassium (K+) ion secretion by way of the kidneys. Among all the hormones made and secreted by the adrenal gland, aldosterone is the primary hormone that works to retain sodium in the body. At the same time, this hormone augments the re-assimilation of sodium as well as water in the body, together with increasing the excretion of potassium in the distal tubes within the kidneys. This action of aldosterone results in an increase in the blood pressure. Aldosterone is the only endogenous (innermost) member belonging to the mineralocorticoids class. This hormone is produced as a result of any enhancement of angiotensin II (also called plasma potassium) that is present at the same level as deficits of sodium. In addition, this hormone is also manufactured in reaction to various cytokines that are secreted owing to hyperthermia.

The secretion of aldosterone is affected by a variety of signals that have to do with adrenocorticotropin hormone (ACTH), atrial natriuretic peptide, melanocyte stimulating hormone as well as plasma concentrations of potassium and sodium, and also by means of a multi-phase sequence of actions known as rennin-angiotensin-aldosterone (RAA) system. Aldosterone receptors are basically proteins, which are present within the cytoplasm of specific kinds of cells, for instance, the fibroblasts found in the aorta and the smooth muscle cells. When aldosterone sets off an aldosterone receptor, it transports the receptor aldosterone complex right into the nucleus of the cell and it, subsequently, attaches to the nuclear chromatin. It is believed that this action results in the modification in the copying of the genes that put into code the proteins that are concerned in the process of the body's retaining sodium and water. The levels of aldosterone lessen as one ages and the secretion of this hormone in aged people is not as much receptive to a vertical posture or reduced ingestion of sodium compared to the young adults.

Aldosterone regulates the sodium as well as potassium levels in the body concurrently, thereby facilitating in the controlling of high blood pressure as well as the body fluids. When the levels of aldosterone are not consistent, it may result in various problems in our body. Elevated levels of this hormone may lead to hypertension, debility and muscle cramps, while poor levels may be a sign of a disease, for instance, diabetes. Time and again, the levels of aldosterone differ depending on the gender and the amount of sodium any individual intakes through his/ her diet may also affect the levels of this hormone in the body. Usually, women have been found to have considerably elevated levels of this hormone when they are pregnant.

It may be noted that the secretion of aldosterone is controlled by rennin, a hormone made by the kidneys. Usually, the levels of rennin as well as aldosterone are evaluated for the purpose of diagnosis. The reason for high or poor levels of potassium in the blood or specific medical conditions like any kidney ailment or heart failure may be found out by taking an aldosterone test.

However, in most cases the levels of aldosterone are found out by taking a blood test. While it is very rare, physicians may also ask for a urine test as an alternative method to determine the aldosterone levels. It is worth mentioning here that physicians may ask people who require undergoing any test to determine their hormonal levels to discontinue specific medicines that may influence the outcome of such examinations, counting hormonal supplements as well as a number of medicines that are used to regulate high blood pressure. In addition, physicians may ask such patients to eat a particular diet for a period of two weeks prior to the examination.

An aldosterone test is taken to calculate the volume of this hormone in blood (serum). This particular test is conducted with the purpose of examining high blood pressure that is difficult to regulate; disorders related to specific body fluids and electrolyte and orthostatic hypotension. The process of measuring aldosterone is helpful in identifying a medical condition known as aldosteronism that is attributable to secretion of surplus amounts of this hormone from the adrenal glands. Very often, the levels of aldosterone in the blood are merged with additional blood tests (such as plasma rennin activity) or proactive tests (such as intravenous saline infusion test, captopril test, or an ACTH infusion test) to find out whether the body is producing this hormone in excessive or poor amounts.

In effect, there are two forms of aldosteronism - primary aldosteronism and secondary aldosteronism. Primary aldosteronism is most often attributable to an adrenal tumour, like in the case of Conn's syndrome, while secondary aldosteronism is more widespread and may develop together with congestive heart failure, specific kidney ailments, cirrhosis by way of ascites (a condition wherein there is a fluid accumulation in the abdominal cavity), taking diets containing very less amount of sodium, surplus potassium, and also toxaemia of pregnancy.

It may be noted that the assessments done through laboratory examinations are likely to differ to some extent and the correctness of the readings of the tests may possibly be subject to appropriate groundwork as may be suggested by the physician. Generally, the medical practitioner will talk about the outcome of the test with the patient and also elucidate on the meaning of the evaluations during the next appointment.

Antihypertensives are drugs that are used to obstruct the secretion or the activities of the hormone aldosterone. Spironolactone is one such medicament that reduces the blood pressure by means of obstructing the aldosterone receptor. The main purpose or consequence of using this drug is to lessen the retention of sodium and water by our body, while enhancing the retention of potassium. In effect, aldosterone is an element of the rennin-angiotensin system.

While the action of the steroid hormone aldosterone is diminished in the case of Addison's disease, it is augmented in Conn's syndrome.

Simpson and Tait were the first to isolate aldosterone in 1953.

Aldosterone functions

It is impossible for humans to stay alive without the hormone aldosterone. This hormone, produced by the adrenal gland, has an important role in the functioning of the kidneys, which clean the blood, eliminating a number of substances into the urine, while retaining the other substances in the body. Aldosterone works to encourage the kidneys to preserve sodium and, hence, additional water in the body, while stimulating the excretion of additional potassium into the urine. In this manner, this steroid hormone facilitates in regulating the blood pressure.

In order to avoid developing cardiovascular diseases, it is essential to take diet that contains restricted amount of cholesterol as well as other fats. Despite this, the fact is that roughly only 25 per cent of our blood cholesterol is obtained from consuming foods having their origin in animals. In reality, the liver as well as additional cells, particularly those in the intestines, comprise the remaining 75 per cent of cholesterol in the bloodstream. Cholesterol forms a vital element for the cell membranes. Our body produces steroids, a vital category of hormones, and the bile acids that facilitate the stomach to assimilate fats from the cholesterol molecules.

The bodily process involved in producing a specific substance, for instance, aldosterone, a steroid hormone, is known as biosynthesis. Hence, the biosynthesis of aldosterone is done in the external segment of the adrenal glands known as the cortex. The adrenal glands are found lying on each kidney. It may be noted that first the adrenal cortex absorbs cholesterol. Subsequently, this adrenal cortex transforms the cholesterol into a series of four different chemicals and, ultimately, into aldosterone. In the end, aldosterone is secreted into our bloodstream.

The feedback loops control the production as well as secretion of hormones, counting aldosterone, in our body. In simple words, this denotes that the augmentation or reduction of a specific substance in our body results in the enhancement or decline in the production as well as release of any hormone. Therefore, this makes it clear that it is essential for our body to sustain a specific cholesterol level in order to make sufficient aldosterone as well as additional steroid hormones. Maintaining a certain level of cholesterol in the body is generally not a problem, unless in the instance of the uncommon genetic ailment called Smith-Lemli-Opitz syndrome, which upsets the ability of our body to produce sufficient cholesterol.

It is worth mentioning here that the majority of the ailments that involve excessive or poor secretion of aldosterone are not attributable to surplus or a deficient level of blood cholesterol. Addison's disease that is attributable to very poor levels of aldosterone and cortisol, is the result of autoimmune damage caused to the adrenal glands. On the other hand, Conn's syndrome is a malady involving excessive production of aldosterone and most often, occurs due to the development of any tumour in the adrenal glands.


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