adrenal cortex
DESCRIPTION
ppt of adrenal cortexTRANSCRIPT
ADRENAL GLAND
ADRENAL CORTEX ADRENAL MEDULLA
Goals for learningGoals for learning
Functional anatomy of adrenal glandHormones and their synthesisFunctions of the hormonesCellular mechanismRegulation of their secretionEffect of their altered secretion
Adrenal glandAdrenal gland Adrenal cortex
– Zona glomerulosa-Mineralocorticoid Aldosterone, Deoxycorticosterone
– Zona fasciculata-Glucocorticoids Cortisol, Corticosterone, Cortisone– Zona reticularis-Adrenal androgens Androsterone, DHEA sulphate Adrenal Medulla
Epinephrine Nor epinephrineDopamine
Cholesterol
Pregnenolone 17 OH Pregnenalone DHEA
Progesterone 17 OH Pregnenalone Andro
stenedione
11 Deoxy 11 DeoxycortisolCorticosterone Testosterone
Corticosterone Cortisol Estradiol
Glucocorticoids Glucocorticoids CortisolCorticosteroneCortisonePredinisolone (synthetic)Dexamethasone (synthetic)
Concentration of cortisol is 13.5 microgram/100 ml, Secretion 15-20mg/day
Transport Cortisol binding globulin(CBG)/ transcortin
GLUCOCORTICOIDSGLUCOCORTICOIDSCORTISOLCORTISOL
This is a C21 steroid produced mainly from zona fasciculata.
It combines with cortisol binding globulin. 96 % of the cortisol is transported in bound form.
Only 4 % is transported in free form.It stays in circulation for 1 to 2 hours.It is degraded in the liver and conjugated to form
glucuronides. It is excreted in urine.
MECHANISM OF ACTIONMECHANISM OF ACTION
These hormones enter the cell and combine with receptors in the cytoplasm. Hormone receptor complex induces portion of DNA to form m RNA.
The m RNA causes protein formation. These proteins are responsible for actions of glucocorticoids.
Onset of action is 45-60 min
FunctionsFunctionsMetabolism CHO, Proteins, Lipids, Mineral and WaterPermissive ActionEffect on ACTH secretionVascular permeabilityOn Nervous SystemOn Blood cells and Lymphatic organsResistance to StressAnti inflammatory and Antiallergic Effects
On carbohydrate metabolismOn carbohydrate metabolism It stimulates gluconeogenesis by the liver by
increasing glucose-6-phosphatase.
It decreases rate of glucose utilization by the peripheral tissues by inhibiting phosphorylation (anti-insulin action)
Increases glycogen synthesis in liver by increasing activity of glycogen synthase.
On protein metabolismOn protein metabolismIt causes protein breakdown in skeletal
muscles.Cortisol enhances amino acid uptake by the
liver cells & enhances transamination - (AA synthesis), deamination – (glucose formation)
Hence proteins like plasma proteins produced by liver are increased
On fat metabolismOn fat metabolism
It causes fatty acid mobilization from adipose tissue increasing free fatty acids in plasma.
It stimulates absorption of lipids from the intestine.
It causes redistribution of fats in the body.
Water and Mineral metabolismWater and Mineral metabolism
Mild mineralocorticoid activity – retains Na & excretes K
Increases angiotensinogen synthesis in liver leading to Na retention via aldosterone
Provides adequate GFR via anti-ADH activity
Permissive actionPermissive actionOn glucagon & catecholamines to exert
calorigenic actionOn catecholamines to exert lipolytic effect
& glycogenolytic effect.On catecholamines to exert pressor
response & bronchodilation.
In stress In stress Offers resistance to StressStress causes increase in ACTH secretion
followed by secretion of cortisolStress causes General Adaptation Syndrome in
2 phases: 1 Stage of Alarm 2 Stage of Resistance: in which cortisol
interacts with catecholamines – activation of sympatho-adrenal medullary system.
Effect on blood cellsEffect on blood cells
EosinopeniaLymphopeniaBasopenia Neutrophilia Polycythemia Platelet count
On BoneOn BoneIt causes demineralization of boneRetards development of cartilageThinning of epiphyseal plateBreaks down bone matrixDecreases calcium depositionIncreases calcium excretionDecreases calcium absorption from GITResults in osteoporosis and tetany
Anti inflammatory & Antiallergic Anti inflammatory & Antiallergic EffectEffect
Pharmacological dosesInhibits Phospholipase A2Reduces the release of arachidonic acid &
consequently reduces the formation of leukotriens, thromboxanes, prostaglandins and prostacyclins.
It reduces leucocyte margination, chemotaxis, phagocytosis of bacteria.
It prevents development of fibroblasts & delays wound healing
REGULATIONREGULATION
Cortisol secretion is controlled by ACTH. ACTH is secreted in irregular bursts
throughout the day. Plasma cortisol rises and falls in response to these bursts. Plasma cortisol is high in mornings (20mg/dl ) and very low (5mg/dl) in evenings.
Trauma Emotions Afferents Circadian rhythm from NTS CRH
cortisol ACTH Adrenal cortex
CUSHING’S SYNDROMECUSHING’S SYNDROMEExcess secretion of glucocorticoids.
Causes Adrenocortical tumours Anterior pituitary tumours Ectopic ACTH producing tumour Prolonged glucocorticoid therapy.
– Cushing’s syndrome caused due to tumours of anterior pituitary is called Cushing’s disease.
Signs & symptomsSigns & symptoms Fat collects in the abdominal
wall, face and upper back producing buffalo hump and moon face.
Skin and subcutaneous tissues are thin.
Muscles are poorly developed.
Wounds heal poorly, minor injuries cause bruises
Osteoporosis occur. There is insulin resistant
diabetes mellitus due to gluconeogenesis .
Signs & symptomsSigns & symptoms There is salt and water
retention, K+ depletion and weakness due to mineralocorticoid activity of cortisol .
Protein depletion occurs due to its excessive catabolism.
Hypertension develops due to increased deoxycorticosterone production.
Reddish purple striae appear in the skin due to rupture of subdermal tissues
TreatmentTreatmentRemoval of tumour in adrenal or pituitary
gland.If removal of pituitary tumour is not
possible, then removal of both adrenals with supplementation of steroids.
SummarySummary
Hormones of Adrenal CortexGlucocorticoids-Mechanism, FunctionsCushing’s Syndrome
Study questionsStudy questionsName the layers of adrenal cortex and list the
hormones secreted by themDescribe the functions of glucocorticoidsWhat is permissive action of a hormone. Give
suitable example?Discuss the anti-inflammatory functions of
glucocorticoidsExplain the cause and clinical features of
cushing’s syndrome