adrenal cortex prof. k. sivapalan. 08-01-14adrenal cortex.2 structure of steroid hormones
TRANSCRIPT
Adrenal Cortex
Prof. K. Sivapalan
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Structure of Steroid Hormones.
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Classification of steroids
• Mineralocorticoids- aldesteron• Glucocorticoids- cortizol• Sex hormones• androgens • estrogens
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Mechanism of Action of Steroids.
• Transport- bound to globulin- Transcortin.• Binds to receptors in cytozol, transported
to Nucleus and act on transcription.• Direct action on membrane and enzymes.
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Glucocorticoids.
• Half-life- 60-90 minutes
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Effects on Carbohydrarte Metabolism.
• In Liver, increases gluconeogenesis. – Increase transport of AA into cells of liver.– Gluconeogenic enzymes increased in liver.– Entry of AA into other tissues prevented.
• Reduces glucose utilization by cells.• The above changes are not seen in Heart,
Brain, and red cells.• Increases blood glucose level.
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Effects on Protein Metabolism.
• Reduce protein synthesis.• Increase catabolism of cellular protein.• Reduce RNA in muscles and lymphoid
tissue.• Increase blood Amino acids.• Increase protein synthesis in liver, plasma
proteins.
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Effects on Fat Metabolism.
• Increased lypolysis from adipose tissue in limbs.
• Fat storage increased in face and trunk.• Increased plasma FFA.
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Other Effects of Glucocorticoids.
• Permissive action:– Catacholamines- calorigenesis, lypolytic
action, pressure responses, bronchodilation.– Glucagon- same as above.
• Vascular reactivity:– Smooth muscle tone requires steroids.– Capillaries require steroids for normal
permeability [absence increases permeability]• Essential for life.
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Other Effects of Glucocorticoids
• Nervous system:– Reduction results in personality changes- irritability,
apprehension and inability to concentrate.– Electroencephalogram changes: slower than normal A
rhythm.– Increase results in reduced threshold for convulsions.
• Water Metabolism:– Deficiency leads to inability to excrete water.
Increased ADH and reduced GFR observed which are repaired by glucocorticoids only.
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Other Effects of Glucocorticoids
• Bone- reduce protein matrix and causes osteoporosis.
• Blood and Immunity:– Increased RBC, nutrophils, platelets.– Reduced eosinophils, basophils, lympho cytes and all
immune responses at high doses.– Use as anti-inflammatory drug.
• Resistance to stress:– High levels of corticoids needed to cope with stressful
conditions. [Essential for life]
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Effects of Mineralocorticoids.
• Half life- 20 minutes.• Distal tubule of kidney- sodium absorption
in exchange of potassium and hydrogen. Blood volume cannot be maintained without this action.
• *Essential for life.• Similar action seen in sweat glands,
salivary glands and gastric glands.
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Effects of Sex Hormones
• Secretion increases at puberty.• Androgens are responsible for acne in
males and females. • All other actions done by sex hormones
secreted by testis and ovary.
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Regulation of secretion.
• Corticotrophin Releasing hormone [CRH] stimulates ACTH which stimulates glucorticoids.
• Renin- angeotensin system regulates aldesteron secretion.
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Diurnal Variation of Secretion.
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Other factors that stimulate CRH
• Trauma- nociceptive pathways• Emotion- lymbic system
– Emotional stresses, fear, anxiety, apprehension
• Baro receptors throw Nucleus Tractus Solitarius inhibit.
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Stimuli that increase aldesteron secretion.
• Glucorticoid also increased,– Surgery.– Anxiety.– Physical trauma.– Haemorrhage.
• Glucocorticoid unaffected:– High potassium intake.– Low sodium intake.– Inferior vena cava constriction in throax.– Standing.– Secondary to congestic cardiac failure, cirrhosis,
nephrosis.
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Adreno Cortical Insufficiency.
• Acute- adrenal crisis:– Head ache, lassitude, confusion,
restlessness, vomiting, abdominal or costo-vertibral pain, circulatory collapse, unconsciousness, death.
• Chronic- Addison’s disease.– Mineralocorticoid insufficiency alone is rare.– Mixed insufficiency is common.
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Addison’s disease.
• Weakness and fatigability.• Weight loss and dehydration.-
– Increased sodium excretion, water diuresis, reduced appetite and GIT function.
• Hypotension and small heart- dizziness, syncopal attacks.
• GIT- reduced acid secretion, reduced motility.• Nervousness and mental symptoms.• Precipitation of crisis in stress.• Pigmentation- depends on the cause.
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Pigmentation due to ACTH.
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Hyper Aldesteronism.
• Primary hyper aldesteronism-– tumor- Conn’s Syndrom.
• Secondary Aldesteronism-– Cardiac failure, renal disease, cirrhosis.
• Hypokalaemia.• Slight increase in ECF and blood volume.• Slight increase in plasma sodium.• Hypertension.
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Hyper Adrenalism- Cushings Disease.
• Redistribution of fat-• Moon face.• Fat pads of neck.• Pendulous abdomen.• Buffalo hump.• Striae in skin.• Thin extremities.
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MOON Face.Same person before and after treatment.Twin sisters with and without moon face.
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Other Features of Increased Glucocorticoids.
• Red face- polycythaemia.• Thin skin, wasting of muscles, osteoporosis-
weakness and backache.• Poorly healing wounds.• Systolic hypertension- sodium retention,
angeotensin increase or direct effect.• Diabetes mellitus.• Mood changes- increased appetite, insomnia,
euphoria, toxic psychosis.• Hypokalaemia- mineralocorticoid action.• Hirsutism- increased androgens.
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Effects if increased Androgens.
• Female fetus- male type of genitalia.• Male fetus- facilitated development of genitalia.• In childhood- stimulation of growth but early
closure of epiphysis and short stature.• Prepubertal boys- precautious puberty without
testicular development.• Adult male- no significant changes.• Pubertal and adult females- male features.
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