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Purple striae or cutaneous abdominal striae or stretch marks – skin and subcutaneous tissue becomes thin due to protein catabolism. The stretching of abdominal skin due t excessive subcutaneous fat deposition causes rupture of subdermal tissues producing reddish purple striae. Muscle weakness and backache due to protein catabolism Sodium and water retention may cause weighjt gain, oedema, and hypertension Hyperglycemia occurs due to gluconeogenesis and inhibition of peripheral utilization of glucose. It may lead to glycosuria and adrenal diabetes. Hirsutism and menstrual irregularity may occur due to adrenal androgens Susceptibility to osteoporosis and bone fracture is increased due to protein depletion and bone resorption Susceptibility to infection is increased due to immunosuppression Psychological and personality changes may occur due to CNS effects of glucocorticoids Blackening of skin may occur due to pigmentation caused by MSH like effects of excessive ACTH 2.Describe the regulation of secretion of cortisol and its physiological role. ( 5 marks) Regulation of cortisol secretion Circadian rhythm of glucocorticoid secretion The secretory rates of Corticotropin releasing factor (CRF), Adrenocorticotropic hormone (ACTH) and cortisol are high in the early morning but low in the late evening. This results from a 24 hour cyclic alteration in signals from the hypothalamus. When a person changes daily sleeping habits, the cycle changes correspondingly. Fig 91-10 Guyton Secretion of cortisol is controlled almost entirely by ACTH secreted by anterior pituitary gland. ACTH secretion is further controlled by corticotrophin releasing factor (CRF) from the hypothalamus. Fig 91-9 Guyton Stress stimuli , the most potent stimuli, activate the hypothalamo-pituitary-adrenal axis to cause rapid release of cortisol. Cortisol then initiates a series of metabolic effects directed towards relieving the damaging nature of the stressful state. Other stimuli such as circadian rhythm and emotions also stimulate the hypothalamo-pituitary-adrenal axis. The hypothalamo-pituitary-adrenal axis regulates glucocorticoid secretion by exerting its effect through CRF ACTH Negative feedback of glucocorticoid (cortisol) secretion Control of CRF secretion
Glucocorticoids thus, exert an anti – insulin effect which leads to hyperglycaemia. When blood glucose increases by 50% or more above normal, the condition is called adrenal diabetes. EFFECT ON FAT METABOLISM
Increases GFR by increasing glomerular plasma flow Rapid excretion of water load Increase in calcium and phosphate excretion EFFECT ON GASTROINTESTINAL TRACT Increases gastric acid secretion and decreases proliferation of gastric mucosal cells. EFFECT ON CNS In absence of cortisol
When androgen precursors are secreted in large amounts for example, in tumour of zona reticularis of adrenal cortex, certain abnormal features are produced. These constitute adrenogenital syndrome. Adrenal androgens exert masculinizing effect, which become prominent when secreted in excess amounts. Adrenal androgens are converted to oestrogen in peripheral tissues and serve as the source of oestrogen in males and postmenopausal females. Characteristic features of adrenogential syndrome are:
Diagnosis – Excretion of 17 – ketosteroids (metabolic end product of androgens) in the urine is 10- times normal Treatment –Treatment with relatively small doses of cortisone is effective in suppressing the excessive secretion of adrenal androgen without causing abnormal metabolic or toxic effects. Genital reconstructive surgery
the same precursor molecule, pro-opiomelanocortin (POMC). MSH normally stimulates melanocytes to produce melanin. In Addison’s disease, deficiency of cortisol leads to increased secretion of ACTH by negative feedback. Stimulant effect of excess ACTH and binding of ACTH to melanin receptors on the melanocytes (MSH like activity) to produce melanin leads to hyperpigmentation 6.physiological basis of permissive action of glucocorticoids ( 2 marks) Glucocorticoids are essential for some physiological actions of other hormones to take place. This is called as permissive action of cortisol ( as cortisol allows the specific actions of these hormones to occur , though it does not produce these effects by itself). They are Vaso pressor and broncho dilator effects of catecholamines Calorigenic effects of glucagon and catecholamines Lipolytic effects of catecholamines