Steroid hormones glucocorticoids

Adrenal gland A triangle-shaped organ positioned at the top of the kidney which functions as a double endocrine gland . The larger outer adrenal cortex secretes three classes of steroid hormones glucocorticoids (e.g., cortisol), minerlocorticoids (aldosterone) and small amounts of sex steroids (e.g., testosterone). The inner adrenal medulla secretes catecholamines (e.g., adrenaline and noradrenaline). 

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. 

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. 

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

Ligand-bound corticosteroid receptors have been shown to interact to form heterodimers with other transcription factors, such as the jun protein. Such interactions are responsible for transactivation of the ds-regulatory sites known as AP-1 sites and for the glucocorticoid-mediated suppression of transcription, such as that seen in the pro-opiomelanocortin gene. A number of such specific protein interactions have been reported these interactions and their locations relative to other transcription factors transform a ubiquitous steroid hormone signal into a tissue-specific, graded cellular response. 

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

Calcium is the major mineral component of bone and normal repair and remodelling of bone is reliant on an adequate supply of this mineral. Calcium uptake in the gut, loss through the kidneys and turnover within the body are controlled by hormones, notably PTH and 1,25 dihydroxy cholecalciferol (1,25 DHCC or 1,25 dihydroxy vitamin D3 or calcitriol). Refer to Figure 8.12 for a summary of the involvement of PTH and vitamin D3 in controlling plasma calcium concentration. These two major hormones have complementary actions to raise plasma calcium concentration by promoting uptake in the gut, reabsorption in the nephron and bone resorption. Other hormones such as thyroxine, sex steroids and glucocorticoids (e.g. cortisol) influence the distribution of calcium. 

I. Replacement therapy. The adrenal cortex (AC) produces the glucocorticoid cortisol (hydrocortisone) and the mine-ralocorticoid aldosterone. 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 11 in particular (p. 124). In AC failure (primary AC insuffiency ... 

Many steroid hormones are regulated by this type of axis—e.g., thyroxin, cortisol, estradiol, progesterone, and testosterone. In the case of the glucocorticoids, the hypothalamus releases corticotropin-releasing hormone (CRH or corticoliberin, a peptide consisting of 41 amino acids), which in turn releases corticotropin (ACTFl, 39 AAs) in the pituitary gland. Corticotropin stimulates synthesis and release of the glandular steroid hormone cortisol in the adrenal cortex. 

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