Adrenal Cortex and its disorders

Adrenal Cortex and its Disorders
Adrenal Cortex 
The adrenal cortex produces two major types of hor­mones: (1) the glucocorticoids, which help regulate the level of glucose in the blood; and (2) mineralocorticoids, which help regulate the level of minerals in the blood. It also secretes a small amount of male sex hormones and a small amount of female sex hormones in both sexes; that is, the adrenal cortex produces both male and female sex hormones in males, and both male and female sex hor­mones in females.
Glucocorticoids 
Cortisol is responsible for the greatest amount of gluco­corticoid activity. Cortisol promotes the hydrolysis of mus­cle protein to amino acids, which enter the blood. This leads to a higher blood glucose level when the liver con­verts these amino acids to glucose. Cortisol also favors me­tabolism of fatty acids rather than carbohydrates. In opposition to insulin (a pancreatic hormone to be dis­cussed shortly), cortisol raises the blood glucose level. Cor­tisol also counteracts the inflammatory response that leads to joint pain and swelling in arthritis and bursitis. The ad­ministration of cortisol aids these conditions because it re­duces inflammation (see the Medical Focus reading on this page).
Cortisol. a glucocorticoid secreted by the adrenal cortex, raises the blood glucose level.
Minera locorticoids 
Aldosterone (al" dos'ter-on) is the most important of the mineralocorticoids. These hormones maintain the elec­trolyte (ion) concentration in blood and, therefore, other body fluids. Aldosterone's primary target organ is the kid­ney, where it promotes renal absorption of sodium (Na+) and renal excretion of potassium (K+). The levels of sodium and potassium in the blood are critical for nerve conduction and muscle contraction; in fact, cardiac failure may result from too iowa level of potassium.
The secretion of mineralocorticoids is not under the control of the anterior pituitary. When the blood volume and blood sodium level is low, the kidneys secrete the en­zyme renin. Renin converts the plasma protein an­giotensinogen to angiotensin 1, which is changed to angiotensin II by a converting enzyme found in the lungs. Angiotensin II stimulates the adrenal cortex to release al­dosterone. The effect of this system, called the renin­angiotensin-aldosterone system, is to raise the blood vol­ume and pressure in two ways. First, angiotensin II constricts the arterioles directly, and second, aldosterone causes the kidneys to reabsorb sodium. When the blood sodium level rises, water is reabsorbed, and blood volume and pressure are maintained.
Two other hormones play a role in the homeostatic maintenance of blood volume.Anti­diuretic hormone (ADH) helps increase blood volume by causing the kidney to reabsorb water. Also, when the atria of the heart are stretched due to increased blood volume, cardiac cells release a hormone called atrial natriuretic (a'tre-al na"tre-u-ret'ik) hormone (ANH), which inhibits renin secretion by the kidneys and aldosterone secretion from the adrenal cortex. The effect of ANH, therefore, is to cause sodium excretion-that is, natriuresis. When sodium is excreted, so is water, and therefore, blood volume and blood pressure decrease.
Aldosterone. a mineralocorticoid secreted by the adrenal cortex. and ADH raise blood volume by causing the kidneys to reabsorb Na+ and vvater. Their action is
opposed by ANH. and in this vvay. normal blood volume is • maintained.
Disorders of the Adrenal Cortex 
Addison Disease A person with a low level of adrenal cor­tex hormones due to hyposecretion develops Addison disease. Typically, symptoms include a peculiar bronzing of the skin. Because the lack of cortisol results in a poten­tially severe drop in blood glucose level, the individual is highly susceptible to any kind of stress due to an insuffi­cient energy supply. Even a mild infection can cause death. Due to the lack of aldosterone, the blood sodium level is low, and the person experiences low blood pres­sure and possibly severe dehydration. Left untreated, Ad­dison disease can be fatal.
Cushing Syndrome A person with a high level of adrenal cortex hormones due to hypersecretion develops Cushing syndrome. Excess cortisol causes a tendency toward dia­betes mellitus, a decrease in muscular protein, and an in­crease in subcutaneous fat. Because of these effects, the person usually has an obese trunk, while the arms and legs remain normal. Due to the high level of sodium in the blood, the blood is basic (pH greater than normal), hypertension occurs, and there is edema of the face, which gives it a moonlike shape. Masculinization may oc­cur in women due to oversecretion of the adrenal male sex hormone.
Addison disease is due to adrenal cortex hyposecretion. Cushing syndrome is due to adrenal cortex hypersecretion.
Hormone secretion and Aging
Although hormone-secreting glands shrink with age, their performance is often unaffected. Thyroid disorders and diabetes are the most important endocrine problems sig­nificantly affecting health and function. Both hypothyroidism and hyperthyroidism are seen in the elderly. Graves' disease, which results from hyperthyroidism, causes symptoms of cardiovascular disease, increased body temperature, and apathy. In addition, there may be a weight loss of as much as 20 pounds, depression, and mental confusion. Hypothyroidism (myxedema) may fail to be diagnosed because the symptoms of hair loss, skin changes, and mental deterioration may be attributed simply to the process of aging.
The true incidence of type II diabetes among the el­derly is unknown. Its symptoms can be confused with those of other medical conditions that are present. Type II diabetes is associated with being overweight and often can be controlled by a proper diet.

Posted in Human Anatomy and Physiology