The adrenal glands are endocrine glands that produce a variety of hormones including adrenaline and the steroids aldosterone and cortisol. They are found above the kidneys. Each gland has an outer cortex which produces steroid hormones and an inner medulla. The adrenal cortex itself is divided into three main zones: the zona glomerulosa, the zona fasciculata and the zona reticularis.
In biology, homeostasis is the state of steady internal, physical, chemical, and social conditions maintained by living systems. This is the condition of optimal functioning for the organism and includes many variables, such as body temperature and fluid balance, being kept within certain pre-set limits. Other variables include the pH of extracellular fluid, the concentrations of sodium, potassium, and calcium ions, as well as the blood sugar level, and these need to be regulated despite changes in the environment, diet, or level of activity. Each of these variables is controlled by one or more regulators or homeostatic mechanisms, which together maintain life.
Calcium channel blockers (CCB), calcium channel antagonists or calcium antagonists are a group of medications that disrupt the movement of calcium through calcium channels. Calcium channel blockers are used as antihypertensive drugs, i.e., as medications to decrease blood pressure in patients with hypertension. CCBs are particularly effective against large vessel stiffness, one of the common causes of elevated systolic blood pressure in elderly patients. Calcium channel blockers are also frequently used to alter heart rate, to prevent peripheral and cerebral vasospasm, and to reduce chest pain caused by angina pectoris.
The renin–angiotensin system (RAS), or renin–angiotensin–aldosterone system (RAAS), is a hormone system that regulates blood pressure, fluid and electrolyte balance, and systemic vascular resistance.
The adrenal cortex is the outer region and also the largest part of the adrenal gland. It is divided into three separate zones: zona glomerulosa, zona fasciculata and zona reticularis. Each zone is responsible for producing specific hormones. It is also a secondary site of androgen synthesis.
Aldosterone is the main mineralocorticoid steroid hormone produced by the zona glomerulosa of the adrenal cortex in the adrenal gland. It is essential for sodium conservation in the kidney, salivary glands, sweat glands, and colon. It plays a central role in the homeostatic regulation of blood pressure, plasma sodium (Na+), and potassium (K+) levels. It does so primarily by acting on the mineralocorticoid receptors in the distal tubules and collecting ducts of the nephron. It influences the reabsorption of sodium and excretion of potassium (from and into the tubular fluids, respectively) of the kidney, thereby indirectly influencing water retention or loss, blood pressure, and blood volume. When dysregulated, aldosterone is pathogenic and contributes to the development and progression of cardiovascular and kidney disease. Aldosterone has exactly the opposite function of the atrial natriuretic hormone secreted by the heart.
Primary aldosteronism (PA), also known as primary hyperaldosteronism or Conn's syndrome, refers to the excess production of the hormone aldosterone from the adrenal glands, resulting in low renin levels and high blood pressure. This abnormality is caused by hyperplasia or tumors. Many experience fatigue, potassium deficiency and high blood pressure which may cause poor vision, confusion or headaches. Symptoms may also include: muscular aches and weakness, muscle spasms, low back and flank pain from the kidneys, trembling, tingling sensations, dizziness/vertigo, nocturia and excessive urination. Complications include cardiovascular disease such as stroke, myocardial infarction, kidney failure and abnormal heart rhythms.
Mineralocorticoids are a class of corticosteroids, which in turn are a class of steroid hormones. Mineralocorticoids are produced in the adrenal cortex and influence salt and water balances. The primary mineralocorticoid is aldosterone.
Adrenal insufficiency is a condition in which the adrenal glands do not produce adequate amounts of steroid hormones. The adrenal glands, also referred to as adrenal cortex normally secretes glucocorticoids, mineralocorticoids, and androgens. These hormones are important in regulating blood pressure, electrolytes, and metabolism as a whole. Deficiency of these hormones leads to symptoms ranging from abdominal pain, vomiting, muscle weakness and fatigue, low blood pressure, depression, mood and personality changes to organ failure and shock. Adrenal crisis may occur if a person having adrenal insufficiency experiences stresses, such as an accident, injury, surgery, or severe infection; this is a life-threatening medical condition resulting from severe deficiency of cortisol in the body. Death may quickly follow.
Adrenocortical carcinoma (ACC) is an aggressive cancer originating in the cortex of the adrenal gland.
Voltage-gated calcium channels (VGCCs), also known as voltage-dependent calcium channels (VDCCs), are a group of voltage-gated ion channels found in the membrane of excitable cells (e.g., muscle, glial cells, neurons, etc.) with a permeability to the calcium ion Ca2+. These channels are slightly permeable to sodium ions, so they are also called Ca2+-Na+ channels, but their permeability to calcium is about 1000-fold greater than to sodium under normal physiological conditions.
Hypoaldosteronism is an endocrinological disorder characterized by decreased levels of the hormone aldosterone. Similarly, isolated hypoaldosteronism is the condition of having lowered aldosterone without corresponding changes in cortisol.
Hyperaldosteronism is a medical condition wherein too much aldosterone is produced by the adrenal glands, which can lead to lowered levels of potassium in the blood (hypokalemia) and increased hydrogen ion excretion (alkalosis).
11-Deoxycorticosterone (DOC), or simply deoxycorticosterone, also known as 21-hydroxyprogesterone, as well as desoxycortone (INN), deoxycortone, and cortexone, is a steroid hormone produced by the adrenal gland that possesses mineralocorticoid activity and acts as a precursor to aldosterone. It is an active (Na+-retaining) mineralocorticoid. As its names indicate, 11-deoxycorticosterone can be understood as the 21-hydroxy-variant of progesterone or as the 11-deoxy-variant of corticosterone.
Pseudohypoaldosteronism (PHA) is a condition that mimics hypoaldosteronism. However, the condition is due to a failure of response to aldosterone, and levels of aldosterone are actually elevated, due to a lack of feedback inhibition.
Aldosterone synthase, also called steroid 18-hydroxylase, corticosterone 18-monooxygenase or P450C18, is a steroid hydroxylase cytochrome P450 enzyme involved in the biosynthesis of the mineralocorticoid aldosterone and other steroids. The enzyme catalyzes sequential hydroxylations of the steroid angular methyl group at C18 after initial 11β-hydroxylation. It is encoded by the CYP11B2 gene in humans.
Steroid 11β-hydroxylase, also known as steroid 11β-monooxygenase, is a steroid hydroxylase found in the zona glomerulosa and zona fasciculata of the adrenal cortex. Named officially the cytochrome P450 11B1, mitochondrial, it is a protein that in humans is encoded by the CYP11B1 gene. The enzyme is involved in the biosynthesis of adrenal corticosteroids by catalyzing the addition of hydroxyl groups during oxidation reactions.
An adrenal tumor or adrenal mass is any benign or malignant neoplasms of the adrenal gland, several of which are notable for their tendency to overproduce endocrine hormones. Adrenal cancer is the presence of malignant adrenal tumors, and includes neuroblastoma, adrenocortical carcinoma and some adrenal pheochromocytomas. Most adrenal pheochromocytomas and all adrenocortical adenomas are benign tumors, which do not metastasize or invade nearby tissues, but may cause significant health problems by unbalancing hormones.
Glucocorticoid remediable aldosteronism also describable as aldosterone synthase hyperactivity, is an autosomal dominant disorder in which the increase in aldosterone secretion produced by ACTH is no longer transient.
Feline hyperaldosteronism is a disease in cats. The symptoms are caused by abnormally high concentrations of the hormone aldosterone, which is secreted by the adrenal gland. The high concentrations of aldosterone may be due directly to a disorder of the adrenal gland, or due to something outside of the adrenal gland causing it to secrete excessive aldosterone.
