Steroid hormones mineralocorticoids

See also Figure 19.24, Cortisol, Figure 23.8, Steroid Metabolism, Steroid Hormone Synthesis, Steroid Hormones, Mineralocorticoids, Steroid and Thyroid Hormones - Intracellular Receptors... 

Steroid Hormones and Neurosteroids. Steroids (qv) can affect neuroendocrine function, stress responses, and behavioral sexual dimorphism (78,79) (see Steroids). Mineralocorticoid, glucocorticoid, androgen, estrogen, and progesterone receptors are localized in the brain and spinal cord. In addition to genomic actions, the neurosteroid can act more acutely to modulate the actions of other receptors or ion channels (80). Pregnenolone [145-13-17, ( ) dehydroepiandosterone [53-43-0] C H2 02 (319) are excitatory neurosteroids found in rat brain, independent of adrenal... 

Steroid hormones can be subdivided into sex hormones (androgens, estrogens, and progestins) and corticosteroids (glucocorticoids and mineralocorticoids). 

FIGURE 25.43 The steroid hormones are synthesized from cholesterol, with intermediate formation of pregnenolone and progesterone. Testosterone, the principal male sex hormone steroid, is a precursor to /3-estradiol. Cortisol, a glucocorticoid, and aldosterone, a mineralocorticoid, are also derived from progesterone. 

Adrenocortical hormone (Section 27.6) A steroid hormone secreted by the adrenal glands. There are two types of adrenocortical hormones mineralocorticoids and glucocorticoids. 

ACE inhibitors do not completely block aldosterone synthesis. Since this steroid hormone is a potent inducer of fibrosis in the heart, specific antagonists, such as spironolactone and eplerenone, have recently been very successfully used in clinical trials in addition to ACE inhibitors to treat congestive heart failure [5]. Formerly, these drugs have only been applied as potassium-saving diuretics in oedematous diseases, hypertension, and hypokalemia as well as in primary hyperaldosteronism. Possible side effects of aldosterone antagonists include hyperkalemia and, in case of spironolactone, which is less specific for the mineralocorticoid receptor than eplerenone, also antiandrogenic and progestational actions. 

The steroid hormones known as mineralocorticoids and glucocorticoids are synthesized in the adrenal cortex of mammals [3]. The physiological mineralocorticoid is... 

Steroid hormones are divided into six classes, based on physiological effects estrogens, androgens, progestins, glucocorticoids, mineralocorticoids and vitamin D 847... 

Angiotensin II has two effects first, as a vasoconstrictor acting via receptors on vascular smooth muscle cells, and second, it stimulates the adrenal cortex gland to produce aldosterone (a mineralocorticoid steroid hormone, see Chapter 4). Aldosterone promotes the reabsorption of sodium from the renal tubule into the bloodstream and the resulting increase in osmolality (osmotic potential) of the blood causes water reabsorption in the nephrons. The outcome is an increase in blood volume and, therefore, pressure which inhibits (by negative feedback) further renin secretion from the JGA. 

The remaining steroid lipids constitute two main classes of steroid hormones sex hormones and adrenocortical hormones. The sex hormones include androgens (testosterone, androsterone), estrogens (estrone, estradiol), and progestins (progesterone). The adrenocortical hormones include mineralocorticoids (aldosterone) and glucocorticoids (hydrocortisone). 

Several biologic ligands are sufficiently lipid-soluble to cross the plasma membrane and act on intracellular receptors. One class of such ligands includes steroids (corticosteroids, mineralocorticoids, sex steroids, vitamin D), and thyroid hormone,... 

The steroid hormones (glucocorticoids, mineralocorticoids, and sex hormones) are produced from cholesterol by alteration of the side chain and introduction of oxygen atoms into the steroid ring system. In addition to cholesterol, a wide variety of isoprenoid compounds are derived from mevalonate through condensations of isopentenyl pyrophosphate and dimethylallyl pyrophosphate. 

Angiotensin II has a variety of effects. By constricting blood vessels it raises blood pressure, and by stimulating thirst centers in the brain it increases blood volume. Both angiotensins II and III also act on the adrenal gland to promote the synthesis and release of aldosterone. Most of the effects of angiotension II are mediated by 359-residue seven-helix G-protein linked receptors which activate phospholipase C.p q qr Like other steroid hormones aldosterone acts,via mineralocorticoid receptors, to control transcription of a certain set of proteins. The end effect is to increase the transport of Na+ across the renal tubules and back into the blood. Thus, aldosterone acts to decrease the loss of Na+ from the body. It promotes retention of water and raises... 

This chapter discusses the pharmacology of the steroid hormones that are produced by the adrenal cortex. The two primary types of adrenal steroids are the glucocorticoids and mineralocorticoids. Small amounts of other steroids such as the sex hormones (androgens, estrogens, and progestins) are also produced by the adrenal cortex. These steroids are discussed in Chapter 30. 

FIGURE 29-1 Pathways of adrenal steroid biosynthesis. Cholesterol is the precursor for the three steroid hormone pathways. Note the similarity between the structures of the primary mineralocorticoid (aldosterone), the primary glucocorticoid (cortisol), and the sex hormones (testosterone, estradiol). See text for further discussion. 

Mineralocorticoids are also steroid hormones that are produced by the adrenal cortex. The principal mineralocorticoid in humans is aldosterone. Aldosterone is primarily involved in maintaining fluid and electrolyte balance in the body. This hormone works on the kidneys to increase sodium and water reabsorption and potassium excretion. 

Mineralocorticoid A steroid hormone (e.g., aldosterone) that is important in regulating fluid and electrolyte balance by increasing the reabsorption of sodium from the kidneys. 

ACTH stimulates the adrenal cortex to produce glucocorticoids, mineralocorticoids, and androgens. ACTH increases the activity of cholesterol esterase, the enzyme that catalyzes the rate-limiting step of steroid hormone production cholesterol - pregnenolone. ACTH also stimulates adrenal hypertrophy and hyperplasia. When given chronically in pharmacologic doses, corticotropin causes increased skin pigmentation. 

Fig. 1 The major classes of steroid hormones progestagens, mineralocorticoids, glucocorticoids, androgens, and estrogens. Enzymes, their cellular location, substrates, and products in human steroidogenesis. Boron WF, Boulpaep EL (2003) Medical Physiology a cellular and molecular approach, p 1300, Elsevier/Saunders (reprinted with permission from Elsevier/Saunders)...

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