Endocrine - Adrenal Disease Flashcards
What is secreted from the Zona Glomerulosa?
What stimulates their secretion?
Mineralocorticoids
- aldosterone
- precursors
Stimulated by:
- angiotensin II
- K+
- ACTH
What is secreted from the Zona Fasciculata?
What stimulates secretion?
Glucocorticoids
- cortisol
- corticosterone
Stimulated by: ACTH IL-1 IL-6 TNF Neuropeptidases
What is secreted from the Zona Reticularis?
What stimulates secretion?
Adrenal Androgens
- DHEA/S
- Andostenedione
Stimulated by:
ACTH
What is secreted from the Adrenal Medulla?
Catecholamines
- adrenaline
- noradrenaline
- dopamine
What is the melanocortin-2 receptor? How does it work?
The ACTH-Receptor MC2R (melanocortin-2 receptor) acts via MC2R-Accessory protein MRAP to form a complex that is transported to the adrenal cortical membrane and binds to ACTH to stimulate cAMP
This results in upregulation of protein kinase A:
1) increased importation of choelsterol esters
2) increased activity of hormone sensitive lipase which cleaves cholesterol esters
3) increased availability and phosphorylation of transcription fractor CREB which ENHANCES SYNTEHSIS OF CYP11A1
Effect of glucocorticoids on liver?
Hyperglycaemia
- stimulates gluconeogenesis
- stimulates glucose production from protein
- stimulates insulin production
Effect of glucocorticoids on muscle?
Catabolism
- mobilisation of amino acids
- inhibition of glucose uptake in muscles
Effect of glucocorticoids on adipose?
Fat deposition
- inhibition of glucose uptake promoting lipolysis
- counteracted y increased insulin stimulating lipogenesis
Effect of glucocorticoids on immune system?
Increased neutrophils
Decreased T and B cells, basophils and eosinophils
Effect of glucocorticoids on bone?
Bone catabolism
- decreased bone formation (direct inhibition of osteoblast)
- stimulation of bone resorption
Effect of glucocorticoids on vascular system?
Increased sensitivity to vasoconstrictors
Mineralocorticoid like effect
Increased free water excretion
Acute and chronic causes of adrenal failure?
Acute: haemorrhage or infarction
- heparin / warfarin
- sepsis
- coagulopathy
Chronic:
- autoimmune adrenalitis
- TB or granulomatous disease
- HIV
- drugs: ketoconazole / etomidate
- congenital adrenal hyperplasia
- adrenoleukodysplasia
- Addison’s
What is adrenoleukodysplasia?
X linked recessive with 2 phenotypes:
1) Cerebral ALD:
- childhood presentation
- dementia, blindness and quadriplegia
2) Adrenomyeloneuropathy
- spasticity and distal polyneuropathy
- young men
To diagnosed: elevated very long chain fatty acids
** screen ANY young boy/man with adrenal insufficiency
Features of glucocorticoid deficiency?
Fatigue, lethargy, weight loss and anorexia
Myalgias and joint pains
Fevers
Hypotension
Normocytic anaemia
Lymphocytosis
Eosinophilia
Hypoglycaemia
Slightly elevated TSH (loss of feedback inhibition)
Hyponatraemia (loss of feedback inhibition of vasopressin release)
Features of mineralocorticoid deficiency?
Abdominal pain, nausea and vomiting
Dizziness
Postural hypotension
Elevated Cr
Elevated K
Hyponatraemia
What are the skin changes in adrenal insufficiency?
PRMIARY: Pigmentation due to excess ACTH melanocytes
But in SECONDARY adrenal insufficiency the skin is PALE due to lack of ACTH
Screening and diagnosis of adrenal insufficiency?
Screen with morning cortisol level
Diagnose with short synacthen test
Gold standard is insulin tolerance test
- contraindicated in epilepsy or IHD
- only interpretable if hypoglycaemia is induced
Once the adrenals are found to be insufficient, how do you differentiate between primary and secondary?
Plasma ACTH:
if HIGH --> primary adrenal insufficiency Should also get: - elevated renin - decreased aldosterone - decreased serum DHEAS
if NORMAL or LOW --> secondary adrenal insufficiency Should also get: - normal renin - normal aldosterone - decreased DHEAS
If a diagnosis of PRIMARY adrenal insufficiency is made with short synacthen test and HIGH ACTH…what is the next step?
Do adrenal autoantibodies, thyroid studies, look for evidence of vitiligo and premature ovarian failure
If above are negative then:
- in males look for very long chain fatty acids
- CT adrenal imaging
If a diagnosis of SECONDARY adrenal insufficiency is made with short synacthen test and LOW/NORMAL ACTH…what is the next step?
MRI pituitary to measure pituitary hormones
What drugs can cause adrenal insufficiency?
by INHIBITING CORTICAL BIOSYNTHESIS:
- etomidate
- ketoconazole
- fluconazole
- metyrapone
- mititane
by INCREASING METABOLISM OF CORTISOL AND SYNTHETIC GLUCOCORTICOIDS:
- phenytoin
- barbituitates
- rifampicin
- mititane
by SUPPRESSING CRH OR ACTH
- glucocorticoids
- megestrol acetate
- opioids
HEPARIN: by HITS is a risk for bilateral adrenal haemorrhage
Etomidate causes adrenal insufficiency how?
by INHIBITING CORTICAL BIOSYNTHESIS:
Phenytoin causes adrenal insufficiency how?
by INCREASING METABOLISM OF CORTISOL AND SYNTHETIC GLUCOCORTICOIDS:
Glucocorticoids causes adrenal insufficiency how?
by SUPPRESSING CRH OR ACTH