Adrenal Gland

ADRENAL GLAND : 

ADRENAL GLAND

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There are two adrenal glands . The two glands have a similarity in anatomical structure , function , secreted hormones and almost in every thing . The two glands are located above the two kidneys , i.e. one gland above each kidney ; exactly at the position of 12 th thoracic vertebra . (A) Position

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So , adrenal glands are also termed , suprarenal glands The term (suprarenal) comes from the anatomic description of the position of the glands as ( supra means above ) while ( renal means belongs to kidney ). On the other side , the term (adrenal) comes from the fact that these glands secrete the hormone (adrenaline) in cases of stress.

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Adrenal gland consists of two distinct parts ; Cortex and Medulla . These two parts differ in their anatomical structure and in their functions (Hormones). (B) Structure

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Cross – sectional view of the adrenal gland

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Adrenal cortex is devoted to the synthesis of CORTICOSTEROID HORMONES due to the presence of large amounts of fats specially cholesterol which is the precursor of these hormones . Adrenal cortex exhibits a functional zonation into three distinct zones ; Cortex

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Zona glomerulosa (2)Zona fasciculata (3)Zona reticularis

(1) Zona glomerulosa : 

(1) Zona glomerulosa The outer most layer of the cortex . It is the main site for production of ( Mineralcorticoids ) The main mineralcorticoid in human is aldosterone while there are some endogenous hormones which have a mineralcorticoid function (progesterone & deoxycorticosterone) .

Aldosterone : 

Aldosterone

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Aldosterone hormone is a derivative of cholesterol . Its normal level is about (4-9 Mg per 100 ml blood) . About 2-18 Mg of aldosterone are wasted with urine daily . Aldosterone acts on kidneys to provide active reabsorption of sodium and passive absorption of water . (increases blood pressure) In addition to that , it causes secretion of both potassium ions and protons from the collecting ducts and distal tubules .

Factors affecting secretion of aldosterone : 

Factors affecting secretion of aldosterone Angiotensin II . Adrenocrticotropic hormone (ACTH) . (3)Blood level of Na and K ions .

DISORDERS OF ALDOSTERONE : 

DISORDERS OF ALDOSTERONE (A) Natural increase in cases of , ( 1 ) Deficiency of sodium and plenty of potassium in the diet . ( 2 ) Heavy sweat . (B) Natural decrease in cases of , ( 1 ) Deficiency of potassium in the diet . ( 2 ) Having large amounts of water and drinks .

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(C) Addison disease Occurs when about 90% of cortex cells are damaged . So , it is very rare ( 8 / million person ) . Addisonian has a remarkable depression in aldosterone level which is accompanied by a low blood pressure , high temperature , weight loss , decreased blood sodium and increased blood potassium .

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(D) Conn disease Occurs due to increased activity of zona glomerulosa . Leads to increased secretion of aldosterone which results in a high blood pressure , low blood potassium and high blood sodium levels .

(2) Zona fasciculata : 

(2) Zona fasciculata The central region of the adrenal cortex . It is the main site for production of ( Glucocorticoids ) The primary glucocorticoid in human is (cortisol) . Zona fasciculata secretes a basal level of cortisol but also produce a small amount of hormone in response to ACTH .

Cortisol : 

Cortisol

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It is usually referred to as the “stress hormone” as it is involved in response to stress and anxiety . Its primary function is to increase blood sugar and stores of sugar in the liver as glycogen . Cortisol also can suppress immune system . Zona fasciculata can produce (7-7.5 mg/day) of cortisol hormone . Highest amount of cortisol can be reached in the early morning (165-744 nM) while the lowest amount occurs approximately at the midnight (83-358 nM) .

Factors affecting cortisol secretion : 

Factors affecting cortisol secretion ( 1 ) Corticotropin releasing hormone (CRH) This hormone controls secretion of adrenocorticotropic hormone (ACTH) . It is secreted from hypothalamus . (2) Adrenocorticotrpic hormone (ACTH) Which is responsible for delivery of calcium ions to cortisol secreting cells in the adrenal cortex .

Physiological effects of cortisol : 

Physiological effects of cortisol ( 1 ) Anti – insulin effect . cortisol contributes to “hyperglycemia” by stimulation of hepatic gluconeogenesis and inhibition of peripheral utilization of glucose . ( 2 ) It increases gastric acid secretion . ( 3 ) It cooperates with adrenaline to create memories of short – term events . ( 4 ) It has an anti – inflammatory action as inhibits secretion of histamine from basophils and mast cells .

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( 5 ) Elevates blood pressure . ( 6 ) Stimulates hepatic detoxification by inducing ; - Tryptophan oxygenase to reduce serotonin level in the brain . - Glutamine synthase to reduce glutamate level in the brain . ( 7 ) Suppresses immune system . ( 8 ) It inhibits secretion of CRH resulting in a feed – back inhibition for ACTH .

Disorders of cortisol : 

Disorders of cortisol (1) Cushing syndrome A hormone disorder caused by high levels of cortisol in the blood . It may be caused by ; ( 1 ) Taking glucocorticoid drugs . ( 2 ) Tumors in cortisol secreting cells . ( 3 ) Tumors in ACTH secreting cells . Cushing syndrome is not confined to humans but relatively common in domestic animals .

Symptoms of Cushing syndrome include ; : 

Symptoms of Cushing syndrome include ; ( 1 ) Rapid weight gain specially from face , trunk and limbs . ( 2 ) very high blood sugar which may lead to diabetes mellitus . ( 3 ) High blood pressure (secondary) . ( 4 ) Osteoporosis due to increased protein breakdown . Cushing syndrome can be treated by surgery .

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( 2 ) Addison disease Deficiency in cortisol level in the blood . Leads to ; ( 1 ) Low blood sugar . ( 2 ) Low blood pressure . ( 3 ) High potassium levels in the blood . ( 4 ) Full body weakness .

(3) Zona reticularis : 

(3) Zona reticularis The interior layer of the adrenal cortex . It is responsible for production of ( Androgens ) and ( Estrogens ) The main adrenal androgen is Testosterone while the main adrenal estrogen is Estradiol .

Testosterone : 

Testosterone

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Testosterone is secreted in both males and females , but in males in a larger amount so , its effects appear clearly on males and therefore , it is the “masculinity hormone” In males , it is secreted mainly from Leyding cells in the testes , and a small amount from adrenal reticularis . In females , it is secreted from Thecal cells in the ovaries , placenta and a small amount from adrenal reticularis . Its activity is mediated by LH and FSH .

D H E A : 

D H E A

Physiological effects of testosteron : 

Physiological effects of testosteron After puberty , testosteron amount in the body increases to cause ; ( 1 ) Development and growth of reproductive organs . ( 2 ) Appearence of secondary sex characteristics such as ; deepening in voice , growth of beard , growth of Adam apple , increase in height , ….etc. ( 3 ) Maintains males fertility .

Estradiol : 

Estradiol

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Estradiol is the predominant sex hormone in females . It is produced primarily by granulosa cells in ovaries , in addition to small amount from adrenal reticularis . During pregnancy , its amount increases due to secretion from placenta also . It is present in males but in lower amounts than females . Its activity is mediated by LH and FSH .

D H E A - S : 

D H E A - S

Physiological effects of estradiol : 

Physiological effects of estradiol ( 1 ) Growth of female reproductive organs . ( 2 ) Maintaining of oocytes in ovaries . ( 3 ) During pregnancy , it promotes uterine blood flow and stimulates breast growth . ( 4 ) Regulation of menstrual cycle . ( 5 ) Affects liver to synthesize lipoproteins , binding proteins and proteins of blood clotting .

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Adrenal medulla is the second part of adrenal gland . Devoted to synthesis of catecholamines which include adrenaline ( epinephrine ) and noradrenaline ( norepinephrine ) . Both hormones are secreted in stressful situations . Medulla

Physiological effects of catecholamines : 

Physiological effects of catecholamines Catecholamines causes general physiological changes that prepare the body for physical activities . In case of ( fight or flight ) , catecholamines cause ; ( 1 ) Elevation of blood pressure . ( 2 ) Increasing blood sugar . ( 3 ) Increasing heart rate . ( 4 ) Increased metabolic rate . ( 5 ) Affects peripheral nervous system .

pheochromocytoma : 

pheochromocytoma Very rare state . A tumor In the adrenal medulla that causes hypersecretion of catecholamines which leads to ; ( 1 ) Hypertension . ( 2 ) Very high blood sugar . ( 3 ) High rate of heartbeat .