Zona glomerulosa, mineralocorticoid

The major mineralocorticoid, aldosterone, is secreted by cells of the zona glomerulosa. Primary hyperaldosteronism (Conn s syndrome) is associated with potassium depletion which is, in mm, responsible for the observed neuromuscular abnormalities seen in the disorder. These are similar to those seen in hypokalemic periodic paralysis (PP), with episodic and severe exacerbations of fixed muscle weakness. Muscle biopsy shows occasional muscle necrosis and vacuoles often these feamres are accompanied by mbular aggregates as in hypokalemic PP. All these changes can be attributed to the hypokalemia and not to excess aldosterone production per se. 

The zona glomerulosa is responsible for the production of the mineralocorticoids aldosterone, deoxycorticosterone, and 18-hydroxy-deoxycorticosterone. Aldosterone promotes renal sodium retention and excretion of potassium. Its synthesis and release are regulated by renin in response to decreased vascular volume and renal perfusion. Adrenal aldosterone production is regulated by the renin-angiotensin-aldosterone system. 

Steroid hormones are produced in the adrenal cortex and the sex glands. All such hormones originate from cholesterol. Figure 16.4 shows the overall scheme for steroid hormone biosynthesis that is applicable to all tissues. The final products may be divided into the following groups mineralocorticoids (e.g., aldosterone), produced by the zona glomerulosa of the adrenal cortex glucocorticoids (e.g., cortisol), produced by the zona fasciculata of the adrenal cortex and the... 

In the adrenal cortex, the outermost zona glomerulosa secretes the mineralocorticoid aldosterone, and corticosterone. The middle zona fasciculata and the inner zona reticularis secrete predominately the glucocorticoids cortisol and corticosterone. In the human, the inner zona reticularis secretes large amounts of the adrenal androgens, DHEA and DHEAS, as well as cortisol [12]. Whereas steroidogenesis in the... 

The adrenal cortex (AC) produces the glucocorticoid cortisol (hydrocortisone) in the zona fasciculata and the mineralocorticoid aldosterone in the zona glomerulosa. Both steroid hormones are vitally important in adaptation responses to stress situations, such as disease, trauma, or surgery. Cortisol secretion is stimulated by hypophyseal ACTH aldosterone secretion by angiotensin II in particular (p. 128). In AC failure (primary adrenocortical insuf ciency, Addison disease), both cortisol and aldosterone must be replaced when ACTH production is deficient (secondary adrenocortical insuf ciency), cortisol alone needs to be replaced. Cortisol is effective when given orally (30 mg/day, 2/3 a.m 1 /3 p.m.). In stress situations, the dose is raised 5- to 10-fold. Aldosterone is poorly effective via the oral route instead, the mineralocorticoid fludrocortisone (0.1 mg/day) is given. 

Q1 Each adrenal gland is composed of an outer cortex and an inner medulla. The cortex consists of three layers where several steroid hormones, synthesized from cholesterol, are produced and secreted. The outer layer of the cortex, the zona glomerulosa, produces the mineralocorticoid aldosterone. The zona fasciculata lies under this layer and, together with the inner layer, the zona reticularis, secretes glucocorticoids, mainly cortisol, corticosterone and androgens. 

Aldosterone is a steroid hormone secreted by the zona glomerulosa of the adrenal gland (Figure 10.3). The steroid hormones are biosynthesized from cholesterol. Aldosterone is called a mineralocorticoid because it regulates the transport of minerals, Na and K. Aldosterone received its name because it contains an aldehyde group —CH=0. 

The mineralocorticoids have a main action on the distal tubules in the kidney to increase sodium absorption, with concomitant increased excretion of K and H. Aldosterone is the main endogenous mineralocorticoid. It is produced in the outermost layer of the adrenal cortex (the zona glomerulosa). An excessive secretion of mineralocorticoids (e.g. in Conn s syndrome) causes marked salt and water retention, with a resultant increase in the volume of extracellular fluid, alkalosis, hyperkalaemia and often hypertension. A decrease in secretion (e.g. Addison s disease) causes a disproportional loss of Na compared to fluid loss, so osmotic pressure of the extracellular fluid is reduced. This results in an increase in intracellular compared to extracellular fluid volume. The concomitant decrease in excretion of K results in hyperkalaemia with some decrease in bicarbonate. The control of synthesis and release of aldosterone is complex and involves both the renin-angiotensin system and the electrolyte composition of the blood. As with other... 

Mineralocorticoid refers to those steroids that regulate salt homeostasis (sodium conservation and potassium loss) and extracellular fluid volume.Aldosterone is the most potent naturally occurring mineralocorticoid and is synthesized exclusively in the zona glomerulosa region of the adrenal cortex. This zone uniquely contains the enzyme aldosterone synthase, an obligatory enzyme in the synthetic pathway to aldosterone. Other adrenocortical steroids that have mineralocorticoid properties with varying degrees of potency include DOC, 18-hydroxy-DOC, corticosterone,... 

The zona glomerulosa also secretes 18-hydroxy-corticosterone, a precursor steroid in the aldosterone biosynthetic pathway. This steroid also has mineralocorticoid properties, but is usually present in the circulation in extremely low concentrations. Mineralocorticoids are also synthesized in the zona fasciculata DOC is the most potent, but corticosterone and cortisol also have weak mineralo-corticoid activity. All of these steroids are synthesized as products of the glucocorticoid pathway. 

Hydroxysteroid dehydrogenase (corticosterone methyloxidase deficiency) Hypotension Restricted to zona glomerulosa sole aldosterone defect hyponatremia, hyperkalemia, increased renin Mineralocorticoid replacement without glucocorticoid replacement... 

A mineralocorticoid secreted by the zona glomerulosa of the adrenal cortex. It is involved in sodium-potassium exchange across all cell membranes, including the distal renal tubules. 

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