Adrenal cortex steroid synthesis


--- Stress is often mentioned by CSS patients around the time of their diagnosis, and in a way this seems related to the adrenal glands as well. A patient in another support group reported reading in "The Stress of Life" by Dr. H. Seyle:.... "the adrenal glands are the processors of stress in our bodies. A person's stress resistance will vary with the competence of his adrenals. Continually stressing them, finally depletes them. When we become exhausted by life, on a mental or physical level, our adrenal glands often fail to keep up, and illness ensues".

In a study of 40 dogs by Kyles, the short-term mortality rate was evaluated in regards to the presence of caval tumor thrombus. Reportedly, tumor thrombus was seen in 25% of all dogs. Eleven percent of adenocarcinomas had tumor thrombus and 55% of pheochromocytomas had tumor thrombus. As mentioned there was no difference in the perioperative death rate regardless of presence or absence of tumor thrombus. The perioperative death rate was 21% for adenocarcinomas and 18% for pheochromocytomas. Previously, pheochromocytomas patients have a high perioperative mortality rate, but the addition of protocols that include administration of high doses of phenoxybenzamine (as high as mg/kg twice daily) have reduced the death rate.

Cells of the zona fasciculata and zona reticularis lack aldosterone synthase (CYP11B2) that converts corticosterone to aldosterone, and thus these tissues produce only the weak mineralocorticoid corticosterone. However, both these zones do contain the CYP17A1 missing in zona glomerulosa and thus produce the major glucocorticoid, cortisol. Zona fasciculata and zona reticularis cells also contain CYP17A1, whose 17,20-lyase activity is responsible for producing the androgens, dehydroepiandosterone (DHEA) and androstenedione. Thus, fasciculata and reticularis cells can make corticosteroids and the adrenal androgens, but not aldosterone.

Corticosteroid biosynthesis has been well characterized, and is presented in simplified form in Figure 62-1 . Cholesterol, the precursor to all steroid biosynthetic pathways, is converted to a variety of steroid molecules in a series of reactions catalyzed by several cytochrome P450 (cyp 450) enzymes. 9 While some cholesterol can be synthesized within the adrenal cortex, the vast majority of cholesterol used in steroid biosynthesis is taken up from a pool of circulating cholesterol bound to low-density lipoproteins in the plasma. After synthesis, corticosteroids are rapidly secreted. Because corticosteroids are not stored in the adrenal cortex, the rate of steroid synthesis is essentially equal to the rate of secretion from the adrenal gland.

Adrenal cortex steroid synthesis

adrenal cortex steroid synthesis

Corticosteroid biosynthesis has been well characterized, and is presented in simplified form in Figure 62-1 . Cholesterol, the precursor to all steroid biosynthetic pathways, is converted to a variety of steroid molecules in a series of reactions catalyzed by several cytochrome P450 (cyp 450) enzymes. 9 While some cholesterol can be synthesized within the adrenal cortex, the vast majority of cholesterol used in steroid biosynthesis is taken up from a pool of circulating cholesterol bound to low-density lipoproteins in the plasma. After synthesis, corticosteroids are rapidly secreted. Because corticosteroids are not stored in the adrenal cortex, the rate of steroid synthesis is essentially equal to the rate of secretion from the adrenal gland.

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