Week 11 Flashcards
What is the origin of the adrenal medulla?
Neural crest
What is the origin of the adrenal cortex?
Mesodermal
What is the physiology/function of mineralocorticoids?
- Regulate salt/electrolyte & water balance
- Na+ retention in kidney to maintain BP
What is the main mineralocorticoid?
Aldosterone
What is the physiology/function of glucocorticoid?
- Affect carbohydrate & protein metabolism
- Potent effects on host defence mechanisms (immunosuppressive & anti-inflammatory)
What is the main glucocorticoid in humans?
Hydrocortisone (also called cortisol)
Why are hydrocortisone actions not completely separate from mineralocorticoid actions?
Because hydrocortisone has equal potency for the mineralocorticoid & glucocorticoid receptors so can have effects on water & electrolyte balance
What 3 things are glucocorticoids used most commonly for?
- Replacement therapy
- Anti-inflammatory
- Immunosuppressive
What does ACTH (from anterior pituitary) stimulate?
Synthesis & secretion of glucocorticoids & mineralocorticoids from adrenal cortex
What does the renin-angiotensin system aid ACTH to promote?
Mineralocorticoid secretion
What synthetic analogue is used instead of recombinant ACTH?
Tetracosactide
What drug is used to mimic the mineralocorticoid effect?
Fludrocortisone
What drug is used to mimic the glucocorticoid effect?
Prednisolone
What is the rate limiting step in the biosynthesis of corticosteroids, mineralocorticoids & sex hormones?
Conversion of cholesterol to pregnenolone (regulated by ACTH)
What drug inhibits the conversion to pregnenolone (rate limiting step)?
Aminoglutethimide
What does the drug Trilostane do?
Blocks 3 beta-dehydrogenase
What is Trilostane used to treat?
Cushing’s & primary hyperaldosteronism
What does the drug Metapyrone do?
Prevents the beta-hydroxylation of C11
What does the drug Carbenoxolone do?
Inhibits the conversion of hydrocortisone to cortisone in the kidney
What is the mechanism of action of Glucocorticoids?
- Bind intracellular receptors migrate to nucleus, dimerize & regulate gene transcription
- Rapid non-genomic effects mediated through signalling systems in cytosol
What are the 3 common glucocorticoids drugs used systematically?
- Hydrocortisone
- Prednisolone
- Dexamethasone
What are the metabolic effects of glucocorticoids mediated by?
By enzymes such as cAMP-dependent protein kinase (PKA) but not all the target genes are known
Describe glucocorticoids regulatory actions on the hypothalamus & pituitary?
Negative feedback on CRF & ACTH leading to reduced release of endogenous glucocorticoids
Describe glucocorticoids regulatory actions of the cardiovascular system?
Reduced vasodilation & fluid exudation
Describe glucocorticoids regulatory actions of the musculoskeletal system?
Decreased osteoblast & increasing osteoclast activity to give a tendency for osteoporosis
Describe glucocorticoids metabolic actions on carbohydrates?
- Decreased uptake & utilisation of glucose accompanied by increased gluconeogenesis to cause hyperglycaemia
- Increased glycogen storage
Describe glucocorticoids metabolic actions on proteins?
Increased catabolism & reduced anabolism particularly in muscle, leading to muscle waste
Describe glucocorticoids metabolic actions on lipids?
Permissive effect on lipolytic hormones & redistribution of fat
Describe glucocorticoids acute inflammatory effect?
Decreased influx & activity of leukocytes
Describe glucocorticoids chronic inflammatory effects?
Decreased activity of mononuclear cells, decreased angiogenesis & fibrosis
Describe glucocorticoids effects on lymphoid tissue?
- Decreased clonal expansion of T & B cells & decreased activation of cytokine-secreting T cells
- Switch from Th-1 & Th-2 responses
Describe/List glucocorticoids actions on mediators of inflammatory & immune responses?
- Decreased production & action of cytokines (interleukins, TNF-α, cell adhesion factors & induced nitric oxide)
- Reduced eicosanoids due to decreased COX-2
- Reduced IgG & complement components in blood
- Increased anti-inflammatory factors (IL-10 & Annexin-1)
Describe the overall action of glucocorticoids on immune systems?
Reduction in activity of innate & acquired immune systems
When would you use glucocorticoids for replacement therapy?
Adrenal failure (Addison’s disease)
When would you use glucocorticoids for anti-inflammatory/ immunosuppressive therapy?
- Hypersensitivity & Asthma
- Topically in inflammatory conditions of skin, eye, ear & throat
- Rheumatoid arthritis, IBD, haemolytic anaemias, idiopathic thrombocytopenia
- Prevent graft-versus host disease
When would you use glucocorticoids for treating cancer?
- Combination with cytotoxic drugs for Hodgkin’s disease & acute lymphocytic leukaemia
- Reduce oedema in tumours (Dexamethasone)
List the adverse/unwanted effects of glucocorticoid therapy?
- Suppress response to infection & injury
- Opportunistic infections can be problematic
- Oral fungal/yeast infections can occur
- Wound healing is impaired
- Osteoporosis
- Hazard of fractures
- Hyperglycaemia
- Muscle wasting & weakness
- Inhibition of growth in children
- Euphoria, depression & psychosis
- Glaucoma
When are adverse/unwanted effects of glucocorticoid therapy commonly found?
Mainly after prolonged systemic use but not following replacement therapy
Describe the potential causes of Cushing’s syndrome?
- Excessive exposure to glucocorticoids
- Disease (tumour) or prolonged administration of glucocorticoid drugs
How common is a pituitary tumour the cause of Cushing’s syndrome?
70% of endogenous cases
How common is an adrenal tumour the cause of Cushing’s syndrome?
15% of endogenous cases
What are the physical signs/symptoms of Cushing’s syndrome?
- Euphoria/ depression
- Buffalo hump
- Thinning of skin
- Thin arms & legs (muscle wasting)
- Osteoporosis
- Hyperglycaemia
- Easy bruising
- Poor wound healing
- Increased abdominal fat
- Moon face, red cheeks
- Cataracts
- Benign intracranial hypertension
What is the main treatment for iatrogenic Cushing’s syndrome?
Decrease/ withdraw use of corticosteroids gradually
What is the main treatment for endogenous Cushing’s syndrome?
- Surgery to remove tumour
- If surgery unsuccessful, or not possible to remove the tumour safely, medication can be used to counter the effects of the high cortisol levels
What happens if Cushing’s syndrome is left untreated?
High blood pressure which increases risk of heart attack & stroke
What is the main clinical use of mineralocorticoids?
Replacement therapy as in Addison’s disease where there is decreased aldosterone secretion
What is the most common mineralocorticoid drug?
Fludrocortisone (oral)
What is the mechanism of action of Fludrocortisone?
- Increases Na+ reabsorption in distal tubules & increases K+ & H+ efflux
- Acts on intracellular receptors that modulate DNA transcription
What is spironolactone?
Competitive antagonist of mineralocorticoids & is a potassium-sparing diuretic
What 4 things is Spironolactone used for?
- Hyperaldosteronism
- Resistant hypertension
- Heart failure
- Oedema
What is Addison’s disease?
Adrenal glands are dysfunctional & lead to cortical insufficiency
Describe the epidemiology of Addison’s disease?
- Rare
- Most 30-50yrs old
- Can occur at any age
- 7 in 10 cases due to autoimmune disease
Describe autoimmune Addison’s disease?
Antibodies destroy adrenal cortex cells which make cortisol & aldosterone
How can TB cause Addison’s disease?
Can spread to & gradually destroy adrenals
What are 4 other causes of Addison’s disease?
- Metastatic cancers
- Atrophy due to prolonged steroid therapy
- Hemochromatosis
- Amyloidosis
List the symptoms of Addison’s disease?
- Anorexia
- Nausea/vomiting
- Weakness
- Hypotension
- Skin pigmentation (due to ACTH)
- Low sodium/high potassium
- Chronic dehydration
- Sexual dysfunction.
What is the treatment for Addison’s disease?
- Corticosteroid (steroid) replacement therapy for life
- Hydrocortisone used to replace cortisol (tablet 2-3x day)
- Prednisolone/ Dexamethasone
What treatment should you give in Addison’s disease if greater mineralocorticoid effects are needed?
Aldosterone is replaced with fludrocortisone, a more selective analogue
What is a cause of primary hyperaldosteronism?
Adrenal adenoma / Conn’s syndrome (80%+)
Describe the treatment for Adrenal adenoma / Conn’s syndrome causing hyperaldosteronism?
- Prior to surgery use aldosterone antagonists (Spironolactone) usually for 4 weeks
- Surgical adrenalectomy, laparoscopic surgery is preferred
Why might hypertension persist after removal of the adenoma in hyperaldosteronism?
Due to effects of previous hypertension on vasculature
Describe how an Adrenal hyperplasia can cause primary hyperaldosteronism?
In bilateral adrenal hyperplasia (BAH) adrenal cells become hyperplastic, resulting in excessive secretion of aldosterone (15%)
How is the rare unilateral adrenal hyperplasia treated?
Adrenalectomy
Describe adrenal carcinoma causing primary hyperaldosteronism?
- Rare
- Only diagnosed once adrenal adenoma removers & examined histologically
Describe congenital adrenal hyperplasia?
- Genetic disorder where C-21 hydroxylase enzyme is missing
- Non-hydroxylated versions of cortisol, corticosterone & aldosterone are made
Why are non-hydroxylated versions of cortisol, corticosterone & aldosterone bad?
Lack normal activity & do not negatively feedback on HPA axis
What does high levels of ACTH cause?
Constant stimulation of production of C-19 androgens
How do you treat congenital adrenal hyperplasia?
- Cortisol to replace missing cortisol & cause negative feedback
- Replace mineralocorticoid
How many different types of arthritis & rheumatic disease are there?
Over 200
What is Rheumatoid arthritis?
- Chronic, systemic autoimmune disease
- Inflammation of lining/synovium of the joints
What may rheumatoid arthritis lead to?
Long-term joint damage resulting in chronic pain, loss of function & disability
Describe the epidemiology of rheumatoid arthritis?
- 3x more common in women
- 30-50yrs, can also affect young
- All ethnic groups & parts of the world
Describe the symptoms of rheumatoid arthritis?
- Inflamed joints are warm, tender, swollen, red & painful & difficult to move
- Fatigue
- Loss of appetite, weight loss, flu-like symptoms, depression, anemia
- Vasculitis
- Sjogren’s syndrome
- Inflammation surrounding heart & lungs
Describe the foot, knee & ankle when affected by rheumatoid arthritis?
Effusions & synovial thickening of knee usually detected easily
How commonly is the hip affected by rheumatoid arthritis?
Common, but early manifestations are not apparent
How commonly are the hands & wrists affected by rheumatoid arthritis?
Affected in virtually all people with RA
Describe the elbow when affected by rheumatoid arthritis?
- Effusion difficult to detect on physical exam
- Only objective finding is loss of motion
Describe the shoulders when affected by rheumatoid arthritis?
Neck stiffness & general loss of motion
Describe how blood is affected by rheumatoid arthritis?
Hypochromatic-microcytic anemia with low serum ferritin & low/normal iron-binding capacity almost universal
in patients with active RA
Describe how nerves are affected by rheumatoid arthritis?
Results from cervical spine instability, peripheral nerve entrapment & vasculitis resulting in mononeuritis multiplex
Describe how the heart is affected by rheumatoid arthritis?
Pericardial effusion present in ~50%, but clinical symptoms are rare
Describe how the lungs are effected by rheumatoid arthritis?
Interstitial lung disease common, but may be asymptomatic
Describe how the eyes are affected by rheumatoid arthritis?
Keratoconjunctivitis sicca, episcleritis, scleritis
Describe how the skin is affected by rheumatoid arthritis?
Rheumatoid nodules in 50%, dermal vasculitic lesions
What are Major histocompatibility complex (MHC)?
Membrane glycoproteins on the cell surface that display peptide antigens to T cells
What is the function of MHC II?
Bind peptides derived from proteins from extracellular sources that have been internalised into intracellular vesicles (DC, macrophage/ phagocytic cells & B cells)
What does class II MHC present?
Peptides to CD4+ T helper cells
What does Th1 produce in general?
Cell mediated immunity
What does Th2 produce in general?
Antibody responses
What do the Th1 cytokines activate?
Macrophages
What do the Th2 cytokines activate?
B cells