ADRENAL GLANDS

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Lecture 1 Dr. Zahoor Ali Shaikh. ADRENAL GLANDS. ADRENAL GLANDS. There are two Adrenal glands, one above each kidney. Adrenal gland has outer cortex and inner medulla. - Outer cortex secrete – steroid hormones - Inner medulla secrete – catecholamine - PowerPoint PPT Presentation

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ADRENAL GLANDS

ADRENAL GLANDSLecture 1Dr. Zahoor Ali Shaikh1ADRENAL GLANDSThere are two Adrenal glands, one above each kidney.Adrenal gland has outer cortex and inner medulla. - Outer cortex secrete steroid hormones - Inner medulla secrete catecholamine (Epinephrine, Nor epinephrine) 2ADRENAL GLANDSAdrenal cortex and adrenal medulla secrete hormones which belong to different chemical categories, whose function mechanism of action and regulation are totally different. Therefore there are TWO endocrine organs in Adrenal gland. We will discuss adrenal cortex and then adrenal medulla.

3ADRENAL CORTEXAdrenal cortex secretes - Mineralocorticoids, Glucocorticoids, Sex hormonesAdrenal cortex has three layers 1. Zona glomerulousa [outer layer] mineralocorticoid - aldosterone 2. Zona Fasciculata [middle layer] 3. Zona Reticularis [inner layer]

4Glucocorticoids & Sex hormones5

ADRENAL CORTEXAdrenal cortex produces number of adrenocortical hormones, all of which are steroids derived from cholesterol.Cholesterol is converted to pregnenolone and then by enzymatic action on pregnenolone, steroid hormones are produced.

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ADRENAL CORTEXAdrenal steroid hormones can be divided into three categories: 1. Mineralocorticoids Aldosterone, it affects mineral that is electrolyte balance [Na+, K+ balance]. 2. Glucocorticoids Cortisol, plays major role in glucose metabolism but also in protein, lipid metabolism and in stress situation. 3. Sex hormones - Testosterone [male sex hormone] - Estrogen [female sex hormone] 8ADRENAL CORTEXAdrenal Steroid hormones [Aldosterone, Glucocorticoids, sex hormones] are all lipophilic, therefore, immediately diffuse through plasma membrane of the cell into the blood.In the blood, - Corticosteroids are carried by Alpha globulin [transcortin]. - Aldosterone and Dehydroepiandrosterone [DHEA] are carried by albumin. 9ALDOSTERONEAldosterone Action & FunctionAldosterone acts on the distal convoluted tubule and collecting tubule of the kidney and causes Na+ absorption and K+ excretion. Na+ retention causes osmotic retention of water and expands ECF [Extra cellular fluid], which is important in long term regulation of blood pressure.10ALDOSTERONEMineralocorticoids are essential for life.WHY ?Because when Mineralocorticoids are NOT there, there will be decrease plasma volume due to decreased Na+ and H2O. It will lead to decreased Blood Pressure and circulatory failure. 11CONTROL OF ALDOSTERONE SECRETIONControl of Aldosterone secretion is through 1. Renin-Angiotensin-Aldosterone system [RAAS] which is regulated by decrease in Na+ and decrease in blood pressure.2. Direct Stimulation of Adrenal cortex by rise in plasma K+ concentration1213

IMPORTANT NOTEACTH from anterior pituitary gland promotes the secretion of Cortisol, but not Aldosterone, therefore regulation of Aldosterone is largely independent of anterior pituitary control.

14GLUCOCORTICOIDSGLUCOCORTICOIDWe will see 1. Metabolic Effects 2. Role in Adaptation of Stress

Metabolic Effects Cortisol plays important role in carbohydrate, protein and fat metabolism. 15

Metabolic Effects

Main function of Glucocorticoids is to increase blood glucose level.HOW ? By Gluconeogenesis conversion of non-carbohydrate sources e.g. amino acids into carbohydrate within the liver. Gluconeogenesis helps to maintain hepatic glycogen stores. Between meals or during fasting glycogen releases glucose in the blood to maintain glucose level. 16Metabolic Effects of GlucocorticoidsGlucocorticoids inhibit glucose uptake by the tissues but not the brain, as brain uses only glucose as its metabolic fuel.Glucocorticoids stimulate protein breakdown in many tissues especially muscle.Glucocorticoids facilitate lipolysis [breakdown of lipid], therefore release fatty acid. 17OTHER ACTIONS OF GLUCOCORTICOIDSCortisol permits catecholamine to induce vasoconstriction.Lack of Cortisol may cause circulatory shock.

NOTEIf any patient is on Cortisol and undergoes surgery, the dose of Cortisol should be increased. 182. Role of Glucocorticoid in Adaptation of StressHow Cortisol helps to adapt to stress ?Precise role is not known, but possible explanation might be In case of stress e.g. surgery, accident, etc. - Increased glucose level by Cortisol will help brain to work [As patient is not eating]. - Increased amino acid by Cortisol will help in tissue repair. - Increased fatty acids available are used by tissue as alternate fuel. 19OTHER EFFECTS OF CORTISOL 1. Anti inflammatory Cortisol blocks the production of inflammatory chemical mediators e.g. leukotrines, prostaglandin. - Cortisol suppresses migration of nuetrophil to the injured side. 2. Immunosuppressive Cortisol inhibits immune response by interfering with antibody production by lymphocytes.

20USE OF CORTICOSTERIODS We use corticosteroids when inflammatory response itself has become destructive e.g. rheumatoid arthritis.In preventing organ transplant rejection. 21SIDE EFFECTS OF CORTICOSTEROIDSAs immune response of the body are suppressed, person has more chances to get infection. OTHER SIDE EFFECTS - Gastric ulcer - High Blood pressure - High Blood sugar - Bone Osteoporosis - Menstrual irregularities 22REGULATION OF CORTISOL SECRETIONCortisol secretion is regulated by ACTH, through negative feedback loop involving Hypothalamus pituitary adrenal cortex axis.

ACTH acts on Zona Fasciculate and Zona Rectilularis. 2324

OTHER FACTORS THAT INFLUENCE CORTISOL SECRETIONDiurnal or Circadian Rhythm Effect Cortisol level is high in the morning [awake] and low at the night [during sleep]. - Circadian Rhythm is regulated by biological clock [suprachismatic nuclei] of Hypothalamus and is related to sleep wake cycle. - Peak and low level are reversed in person who works at night and sleeps during the day. 25ADRENAL CORTEX SEX HORMONESIn both sexes [male and female] adrenal cortex produces both androgens [male sex hormone] and estrogens [female sex hormone].Under normal conditions, adrenal androgens and estrogens are not so abundant to induce masculinizing or feminizing effects.

26ADRENAL CORTEX SEX HORMONESIn female, adrenal androgen is responsible for androgen dependent processes e.g. pubertal growth spurt, Growth of axillary and pubic hair. Development and maintenance of sex drive 27CONTROL OF ADRENAL CORTEX ANDROGENSIt is ACTH that controls adrenal androgen secretion [not the pituitary gnadotropic hormone].In female, at the time of puberty, adrenal androgen secretion increases which initiates the development of androgen dependent processes. 28WHAT SHOULD YOU KNOW FROM THIS LECTURE?Adrenal Gland LayersSecretion of Steroids Hormones by each layerAldosterone Action & FunctionControl of Aldosterone SecretionGlucocorticoids metabolic effects, role in stressGlucocorticoids other effects Anti-inflammatory and ImmunosuppressiveSide Effects of CorticoidsRegulation of Cortisol Secretion, Diurnal RhythmSecretion of Sex hormones by adrenal cortex and their control 29THANK YOU30