Adrenocorticotrophic hormone secretion

Neuroendocrine Reduces testicular production of testosterone Enhances target responsivity to gonadotropins Reduces LH and prolactin secretion Increases adrenocorticotrophic hormone levels Increases corticosterone levels... 

The adrenocorticotrophic hormone ACTH (corticotropin) stimulates the adrenal cortex to secrete the glucocorticoids hydrocortisone (cortisol) and corticosterone, the mineralocorticoid aldosterone, and a number of weakly androgenic substances, as well as a small amount of testosterone. Aldosterone synthesis is also regulated by renin and angiotensin. 

Pituitary activity is absolutely central to osmoregulation, and hypophy-sectomy destroys the ability of fish to adapt to a change in salinity. The prolactin is synthesized in, and is secreted by, the pituitary, which also secretes adrenocorticotrophic hormone (ACTH), which, in turn, stimulates the adrenals to produce cortisol. The level of ACTH in the plasma is therefore raised when fish are in sea water (Nichols and Fleming, 1990). The pituitary also secretes growth hormone into the blood plasma in sea water (Yada and Hirano, 1992 rainbow trout) but its role is not clear in the present context. 

Figure 18.5. Endocrine-immune relationship following chronic stress. In chronic stress, the hypothalamic-pituitary-adrenal (HPA) axis is up-regulated with a down-regulation of its negative feedback control. Arginine vasopressin (AVP) is secreted from the hypothalamus and induces the release of adrenocorticotrophic hormone (ACTH) from the pituitary. ACTH interacts with receptors on adrenocortical cells and cortisol is released from the adrenal glands adrenal hypertrophy can also occur. Release of cortisol into the circulation has a number of effects, including elevation of blood glucose. Unlike in acute stress, the negative feedback of cortisol to the hypothalamus and pituitary is impaired. This leads to continual activation of the HPA axis and excess cortisol release. Cortisol receptors become desensitized leading to increased activity of the pro-inflammatory immune mediators.

Prednisolone - The stress of surgery causes an increase in plasma adrenocorticotrophic hormone and cortisol concentrations. Cortisol secretion can rise from 30 mg/day to 50 mg/day following minor surgery and 150 mg/day following major surgery. However, an abrupt withdrawal after a prolonged period may lead to acute adrenal insufficiency, hypotension or shock. Thus it is important to continue SC s corticosteroid therapy and additional intravenous hydrocortisone may be administered peri-operatively. 

Q4 Glucocorticoid secretion is controlled by the hypothalamus and anterior pituitary gland. Corticotrophin releasing factor (CRF) is produced in the hypothalamus and travels in the hypophyseal portal blood vessels to the anterior pituitary to release ACTH (adrenocorticotrophic hormone). There is a daily (circadian) rhythm in CRF and ACTH secretion, with a peak in the morning between 7 and 9 a.m. and a low point during the night. 

ACTH adrenocorticotrophic hormone is a peptide hormone released by anterior pituitary cells in response to stressful stimuli that causes the synthesis and release of cortisol (corticosteroid) from the adrenal cortex. It is an important component of the hypothalamic-pituitary-adrenal (HPA) axis. ACTH is released from pro-opiomelanocortin and secreted from corticotropes in response to corticotropin-releasing hormone (CRH) released by the hypothalamus. 

ACTH( adrenocorticotrophic hormone) acts specifically on the adrenal cortex to elicit secretion of cortisol. Disorders of the hypothalamic-pituitary -adrcnal axis are described in detail on pages 86-91. 

Cortisol is produced in the zona fasciculata and zona reticularis of the adrenal cortex, the end prixluct of a cascade of hormones which make up the hypothalamic-pituitary-adreniKortical axis (Fig. 2). Corticotrophin releasing hormone (CRH) is secreted by the hypothalamus under the influence of cerebral factors. Adrenocorticotrophic hormone (corticotrophin. orsimply ACTH) is secreted by the anterior pituitary under the control of CRH to maintain the fa.scicular and reticular zones of the adrenal cortex and to stimulate the secretion of cortisol. Ilypolhalamie secretion of CRH and pituitary secretion of ACTH are modulated by cortisol in negative feedback liwps. 

The biosynthesis and secretion of these adrenal cortical hormones are influenced by the hypothalamus-pituitary axis and the adrenocorticotrophic hormone (ACTH) and its associated feedback mechanisms (Figure 10.3.1). The secretions of ACTH are pulsatile, and they are influenced more by the central nervous system and the pituitary gland than the glucocorticoid feedback mechanisms. 

Hormones, such as the adrenocorticotrophic hormone (ACTH), appear to regulate the concentration of zinc in the liver. ACTH, secreted by the anterior pituitary gland, stimulates the secretion of... 

This secretes the following hormones Adrenocorticotrophic hormone Follicle stimulating hormone Growth hormone Luteinizing hormone Melanocyte stimulating hormone Prolactin... 

The glucocorticosteroids and mineralocorticosteroids are produced in the adrenal gland. The major glucocorticosteroids are cortisol (hydrocortisone), cortisone and corticosterosterone. The natural glucocorticosteroids are important because of their involvement in the control of metaholism of fats, carbohydrates and proteins (Fig. 20.35). Additionally, they play important roles in inflammation, the immune system and in the stress response. Production of these hormones is under the control of adrenocorticotrophic hormone (ACTH), which is secreted by the pituitary, and this influences the adrenal gland to produce cortisol, etc. 

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