Adrenal gland and its hormones

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Adrenal gland and its hormones Dr.Abhijit Gogoi University of Fiji

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Adrenal Glands

Adrenal gland and its hormones: 

The Adrenal Gland Anatomy was first described in 1563. Is located above (or attached to) the upper pole of the kidney. Is pyramidal in structure and weights about four grams. Consists of the adrenal cortex and adrenal medulla Activities are regulation of fluid volume and stress response

Adrenal Glands : 

Adrenal Histology

The Adrenal Gland: 

Adrenal Cortex Is divided into 3 zones in the adult gland: Zona Glomerulosa, Zona Fasciculata, Zona Rericularis. Is divided onto 4 zones in the fetal gland. The three zones of the permanent cortex constitutes only 20% of the fetal gland’s size. The remaining zone (fetal cortex) comprises up to 80% of gland’s size during fetal life.

Adrenal Histology: 

Zona Glomerulosa Al dosterone

Zona Glomerulosa : 

Zona Fasciculata Hydrocortisone/cortisol

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Zona Reticularis Gonadocorticoids

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Aldosterone, sex hormones, cortisol Synthesized from cholesterol–steroid ring Adrenal Cortex: Steroid Hormone Production

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INTRODUCTION: The adrenal glands are located near eachkidney and consists of two distinct parts , a ) Adrenal medulla adrenal medula contains Chromaffin cells ( pheochromocytes ). Chromaffin cells secrete the catecholamines epinephrine and norepinephrine Release of catecholamines has been characterized as a “fight or flight” response Catecholamines promote hyperglycemia b ) Adrenal Cortex Cortex synthesize a number of steroid hormones. 80% of an adrenal gland’s total weight. The production of these adrenocortcal hormones or Corticoids has been controlled by the hormone ACTH ( Adrenocorticotropic hormone ) which is produced in the anterior lobe of the pituitary.

Adrenal Cortex: Steroid Hormone Production: 

Corticosteroids 1)Predominantly glucocorticoid activity Cortisol,corticosterone and 11dehydrocorticosterone 2)Predominantly mineralocorticoid activity Aldosterone and 11 deoxycorticosterone 3)Androgenic activity: DHEA,DHEAS and androstenedione

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DHEA is converted in adipose tissues to potent androgens like testosterone and dihydrotestosterone and also estrogens. In males 85% of estrogen comes from peripheral conversion and only 15% from testes. Estrogens hastens the closure of epiphysis,enhances the secretion of GH at puberty,inhibition of gonadotrophic hormones and regulate the HDL

Corticosteroids: 

In premenopausal women,60% of estrogen comes from ovaries and 40% from peripheral conversion. In postmenopausal women it mainly comes from peripheral conversions. The whole conversion depends upon the mass of adipose tissues.

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Adrenal Cortex: Steroid Hormone Production Figure 23-2: Synthesis pathways of steroid hormones

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Physiologic actions of glucocorticoids 1)effect on blood cells: Stimulates hemopoiesis and increases RBCs,neutrophils and platelets. 2)anti-inflammatory effects: By stabilising lysosomal membranes and inhibiting release of proteolytic enzymes. By decreasing capillary permeability and inhibiting leucocytic diapedesis By inhibiting release of serotonin,mast cells,histamine and macrophages

Adrenal Cortex: Steroid Hormone Production: 

3)anti-immunity effects: Cause involution of lymphnodes,thymus and spleen 4)Anti allergic effect 5)Renal effects: Facilitate rapid excretion of water load and also uric acid excretion 6)Gastric effect:increases gastric acid secretion

Physiologic actions of glucocorticoids: 

7)psycho-neural effects: High cortisol can cause irritability,depression,insomnia,amnesia and seizure 8)Vascular effect: Enhances catecholamines effect and maintains normal BP 9)Stress adaptation 10)ADH secretion Negative feedback on ADH

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11)metabolic effects: Hyperglycemia Release of amino acids from proteins Lipolysis in adipose tissues Increases total body fat and causes redistribution of fats

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Cortisol Effects: Body Responses to Stress Permissive effect on glucagon Memory, learning & mood Gluconeogenesis Skeletal muscle breakdown Lipolysis, calcium balance Immune depression Circadian rhythms

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Cortisol Effects: Body Responses to Stress Figure 23-4: Circadian rhythm of cortisol secretion

Cortisol Effects: Body Responses to Stress: 

Control of Cortisol Secretion: Feedback Loops Figure 23-3: The control pathway for cortisol External stimuli Hypothalamic Anterior Pituitary Adrenal cortex Tissues

Cortisol Effects: Body Responses to Stress: 

Cortisol: Role in Diseases and Medication Use as immunosuppressant Hyperimmune reactions (bee stings) Serious side effects Hypercortisolism (Cushing's syndrome) Tumors (pituitary or adrenal) Iatrogenic (physician caused) Hypocortisolism (Addison's disease)

Control of Cortisol Secretion: Feedback Loops: 

Cortico steroid therapy and its uses 1)in adrenal insufficiency 2)treatment of rheumatoid arthritis and collagen disorders 3)in organ transplant recipients for reducing graft rejection 4)used in bronchial asthma and skin disease 5)used in leukaemis 6)to treat cerebral edema and in treatment of circulatory shock

Cortisol: Role in Diseases and Medication: 

Cushings syndrome Hypersecretion of cortisol Mostly by ACTH secreting pituitary tumors Moon fat,truncal obesity with pendulous abdomen and buffallo hump Due to increase in catabolism,there is osteoporosis of bone,atrophy of muscles and thinning of skin. Reddish purple striae due to stretching of skin Easy bruisability and poor wound healing

Cortico steroid therapy and its uses: 

Cushings syndrome Amenorrhoea and hirsutism in females Impotency in males And decrease libido in both Hypertension due to sodium retention Glucose intolerance Hyperlipidaemia and hyper cholesterolaemia

Cushings syndrome: 

Excess cortisol cause obesity Buffalo like torso Moon face Caused due to excess stimulation of food intake & fat being generated more rapidly than mobilized & oxidized

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Mineralocorticoids : Aldosterone exerts the 90% of the mineralocorticoid activity. Cortisol also have mineralocorticoid activity, but only 1/400 th that of aldosterone Aldosterone increases renal tubular (principal cells) reabsorption of sodium & secretion of potassium Excess aldosterone ↑ ECF volume & arterial pressure, but has only a small effect on plasma sodium concentration Excess aldosterone causes hypokalemia & muscle weakness, & too little aldosterone causes hyperkalemia & cardiac toxicity Excess aldosterone increases tubular (intercalated cells) hydrogen ion secretion, with resultant mild alkalosis Aldosterone stimulates sodium & potassium transport in sweat glands, salivary glands, & intestinal epithelial cells

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Synthesis of Aldosterone

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Other examples of mineralocorticoids : Adrenal Disorders Pheochromocytoma tumor of adrenal medulla, with hypersecretion of (nor-)epinephrine causes  BP,  metabolic rate, hyperglycemia, glycosuria , nervousness, indigestion, sweating

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Aldosterone Exclusively synthesized in Z. Glomerulosa Essential for life. Promotes sodium retention and Potassium elimination by the kidney. Expands ECF volume

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Regulation of Aldosterone Secretion

Aldosterone: 

Adrenal insufficiency 1)primary adrenal insufficiency: Is called as Addisons disease Deficiency of cortisol,aldosterone and DHEA Hypoglycemia and hyperpigmentation Hyponatremia and hyperkalemia and metaboloic acidosis 2)secondary adrenal insufficiency

Regulation of Aldosterone Secretion: 

Conn’s syndome Primary aldosteronism due to adenoma Hypokialemia and hypernatremia

Adrenal insufficiency: 

Aldosterone: Role in diseases Complete failure to secrete aldosterone leads to death (dehydration, low blood volume). Hyperalsdosterone states: Contribute to hypertension associated with increased blood volume.

Conn’s syndome: 

Sympathetic stimulation Catecholamine release to blood Epinephrine Norepinephrine Travel to: Multiple targets Distant targets Adrenal Medulla: A Modified Sympathetic Ganglion

Aldosterone: Role in diseases: 

Adrenal Medulla: A Modified Sympathetic Ganglion Figure 11-10: The adrenal medulla

Adrenal Medulla: A Modified Sympathetic Ganglion: 

Catechalomines: Activity Stimulates the “fight or fight” reaction Increased plasma glucose levels Increased cardiovascular function Increased metabolic function Decreased gastrointestinal and genitourinary function

Catechalomines: Activity: 

Cushing syndrome (adrenal tumor, excess ACTH) causes hyperglycemia, hypertension, weakness, edema muscle, bone loss with fat deposition shoulders + face Adrenogenital Syndrome (AGS): Androgen hypersecretion causes enlargement of penis or clitoris and premature onset of puberty. Prenatal AGS in girls can result in masculinized genitals (photo) AGS in women can result in deep voice, beard, body hair