Adrenal Gland PDF

FLG 171: Endocrinology Dr Gumede [email protected]  Learning outcome 1.5 The endocrine role of the adrenal glands  Adrenal glands Adrenals/suprarenals On top of the kidneys Each gland - supplied by superior, middle & inferior suprarena...

FLG 171: Endocrinology Dr Gumede [email protected]  Learning outcome 1.5 The endocrine role of the adrenal glands  Adrenal glands Adrenals/suprarenals On top of the kidneys Each gland - supplied by superior, middle & inferior suprarenal arteries  Adrenal Gland - structure Consist of medulla & cortex Medulla (Inner part) - constitutes 20% (Epinephrine & norepinephrine Cortex (Outer part) - constitutes 80% Corticosteroids Synthesized from cholesterol 1. Mineralocorticoids 2. Glucocorticoids 3. Androgens  Adrenal cortex Zona glomerulosa - Mineralocorticoids (Aldosterone) Zona fasciculata - Glucocorticoids (Cortisol) Zona reticularis - Androgens (Androstenedione  Mineralocorticoids Aldosterone = major mineralocorticoid hormone Aldosterone - mainly targets kidneys (renal tubules) Maintenance of normal ECF volume/ osmolarity Stimulus: low Na+ Renin-Angiotensin  Aldosterone KIDNEY (Distal tubules & collecting tubules) Na+ retention K+ excretion Water retention Consequence of Na+ retention= expands blood volume Regulates BP H+ excretion Affects acid-base balance  Control of Aldosterone secretion Also, Renin -Angiotensin Aldosterone Hypersecretion (Conn’s syndrome) Causes Adrenal tumour (zona glomerulosa) Chronic liver failure ( aldosterone breakdown) Consequences Aldosterone Na+ retention= blood volume and hence BP K+ excretion= arrhythmias & skeletal muscle weakness (hyperpolarise) Water retention= blood volume, overhydration and hence BP H+ excretion = metabolic alkalosis: body pH elevated  Aldosterone Hyposecretion Addison’s disease Autoimmune destruction of cortex Signs: Hyperkalemia Hyponatremia Can lead to decreased ECF volume – shock/low BP (Addisonian crisis) Glucocorticoids Cortisol = main glucocorticoid hormone Targets various tissues Functions/Effects Stimulates gluconeogenesis Therefore, increases blood glucose Suppresses immune system Anti-inflammatory effects Cortisol: mechanism of action Body responses to stress Permissive effect on glucagon Brain function: memory, learning & mood Gluconeogenesis Protective against hypoglycemia Skeletal muscle breakdown Lipolysis, negative calcium balance Immune depression Circadian rhythms: highest level in morning Regulation of Cortisol secretion  Cortisol Hyposecretion Addisons disease Signs & symptoms: Weight loss Hypoglycaemia  Cortisol Hypersecretion: Cushing’s disease Consequences: CRH/ACTH or tumor Blood glucose ( insulin & gluconeogenesis) Protein ( protein catabolism) - thin limbs, skeletal muscle; fatigue & muscle weakness Body weight (extra glucose deposited as fat in trunk, facial & cervical areas) called truncal obesity, moon face & buffalo hump Bone calcification ( activation of Vit. D, Ca2+ absorption from GIT) together with matrix results in osteoporosis TPR & Cardiac contractility( Epinerphrine) Suppression of immune system Cushing’s disease  Adrenal Medulla Adrenal Medulla produces mainly Adrenaline Also known as Epinephrine Noradrenaline is also released Also known as Norepinephrine Biosynthesis & Release chromaffin cells L-tyrosine tyrosine hydroxylase L-dopa dopa decarboxylase dopamine dopamine β-hydoxylase Noradrenaline methyltransferase Adrenaline  Some Effects of Adrenaline – Fight or flight Increase cardiac output Increase metabolic rate Increase Gluconeogenesis Vasoconstriction – in some vessels Increase respiratory rate Bronchodilation  Hypersecretion Increased heartbeat Palpitations High blood pressure Increased blood glucose Excessive sweating Summary 1. Aldosterone stimulates re uptake of Na and excretion of K + and H 2. Excess aldosterone (Conn’s syndrome) causes increased blood pressure (Na uptake), abnormal action potentials and heart problems (K excretion). 3.Lack of aldosterone leads to low blood pressure (Na loss) and abnormalities in function of nerves, muscles and heart (increased K and H+). 4. Cortisol stimulates conversion of muscle protein to glucose and increases plasma glucose levels. 5.Cortisol facilitates lipolysis, but it also increases appetite and stimulates fat deposition in specific tissues. 6.Cortisol increases the vascular response to adrenaline and angiotensin II, increasing blood pressure. 7.Glucocorticoid excess (Cushing’s disease) favours development of diabetes mellitus (increased glucose, insulin insensitivity), atherosclerosis (hyperlipidemia, blood pressure), infection (immune suppression) and causes weakened muscles, bones, connective tissue and blood vessels (proteolysis). 8.Lack of cortisol causes hypoglycaemia, loss of muscle and weight,