Flashcards in Endocrinology 4 - Adrenology Deck (67):
What are the zones of the adrenal cortex, and what do they produce?
Glomerulosa - Mineralocorticoids
- aldosterone and precursors
- in response to ATII, K and ACTH
Fasciculata - Glucocorticoids
- in response to ACTH (Il-1, Il-6, TNF and neuropeptides)
- Adrenal androgens - DHEA/S, androstenedione
- in response to ACTH
What is produced in the adrenal medulla?
- Adrenaline (metanephrine)
- Noradrenaline (normetanephrine)
What are clinical features of 'non-classical' CAH?
Females with precocious puberty
Androgen excess (hirsuit, oligmenorrhoea, acne, infertility)
Random 17-OH progesterone may be normal
17-OH-P >45nmol/L post synacthen - Diagnostic
Rx often not needed - antiandrogens for troublesome hisruitism, glucocorticoid/stress not required, ovulation induction.
What are characteristics of cortisol, and what does this mean for screening excess/deficiency?
Highest at 8am - check here for adrenal failure
Lowest at 0000 - check here for cushing's
What is cortisol bound to, and what influences this?
90-95% bound to plasma proteins
- 80% corticosteroid binding globulin (CBG)
- 10-15% serum albumin
Pregnancy, oestrogen, hyperthyroidism, inflammation increase CBG
Hypothyroidism, protein deficiency, diminished synthetic capacity (genetics)
CBG inversely proportional to insulin
What are clinical Symptoms of Addison's Disease?
NV abdo pain
What are signs of Addison's Disease
Hypotension, dehydration (disproportionate)
loss of axillary and pubic hair (F)
What are Lab findings in addison's disease?
T4 low, elevated TSH
What happens to cortisol and aldosterone in addison's?
- increased ACTH - pigmentation
- weight loss from anorexia
- increased renin
- hyperchloraemic acidosis
- decreased H20 retention, weight and BP
What are causes of primary adrenal insufficiency?
Acute - haemorrhage or infarction of adrenals
- Autoimmune disease adrenalitis
- Infection -TB, AIDS
- Cancer - lymphoma, metastases
- Drugs - ketoconazole, etomidate
- Other - congenital adrenal hyperplasia
- Adrenoleukodystrophy (Males)
What are causes of secondary adrenal insufficiency?
- pituitary apoplexy
- pituitary/hypothalamic surgery
- autoimmune disease - lymphocytic hypophysitis
- infectious disease - TB
- Cancer - pit/hypothalamic tumours/lymphoma
- Trauma - TBI, SAH, Radiation
- Drugs - megestrol acetate
- discontinuation of exogenous steroids
- empty sella syndrome
What is associated with HITTS?
bilateral adrenal haemorrhage
What is the first test in excluding adrenal insufficiency?
Early morning cortisol - if >550, reasonably exludes if patient not on glucocorticoids. 250-500 is probably sufficienct.
What is the role of the short synacthen test in adrenal insufficiency?
If cortisol is >550 at 30 or 60 minutes, reflects normal adrenal function in a well patient.
What is the role of the insulin tolerance test in adrenal insuffciency?
Gold standard test for ACTH/GH reserve.
only interpretable if hypoglycaemia induced 500, GH >20.
What is the significance of high ACTH and renin?
Indicates primary adrenal insufficiency (loss of aldosterone secretion)
When is imaging not indicated in adrenal disease?
IF there is associated autoimmune disease, adrenal autoantibodies.
What is the significance of autoimmune polyglandular syndrome?
If a diagnosis of primary hypothyroidism is made, but miss coexisting adrenal insufficiency, commencing thyroid replacement therapy can precipiate an adrenal crisis - given thyoroxine accelerates the metabolic clearance of cortisol.
What are features of Autoimmune polyendocrine syndrome type I?
Due to AIRE defect.
What are principal features of Autoimmune polyendocrine syndrome type II?
Diabetes mellitus type 1
What is the mechanism of Autoimmune polyendocrine syndrome?
failure of normal thymic negative selection with autoreactive T-cells escaping to the periphery.
What are features of adrenoleukodystrophy?
X-linked recessive disorder
- Cerebral ALD
- childhood presentation
- dementia, blindness, quadriplegia
Elevated very long chain fatty acids
Screen in any young man with adrenal insufficiency
What are features of adrenomyeloneuropathy?
X-linked recessive disorder
- spasticity, distalpolyneuropathy
- young men
Diagnosis - elevated very long chain fatty acids
Screen in any young man with adrenal insufficiency
What duration and dose of prednisone is required to cause HPA suppression?
>5mg/day of pred for >4 weeks
Morning admin less likely to suppress vs nighttime admin.
Full recovery can take 12 months. HPA 2-5months, full adrenal function 9-12months
SST most commonly used method to test adrenal/HPA suppression.
What is the effect of glucocorticoids on the liver?
- glucose production from protein
- increased pancreatic insulin pdn
What is the effect of glucocorticoids on muscle?
- mobilisation of AA
- inhibition of glucose uptake
What is the effect of glucocorticoids on fat tissue?
- inhibition of fat uptake promoting lipolysis
- counteracted by increased insulin stimulating lipogenesis
What is the effect of glucocorticoids on the immune system?
- increased Neutrophils, decreased T/B lymphocytes, basophils, eosinophils
What is the effect of glucocorticoids on bone?
- decreased bone formation by direct inhibition of osteoblasts
- stimulation of bone resorption
What is the effect of glucocorticoids on vascular/fluid balance?
- increased sensitivity to vasoconstrictors
- mineralocorticoid like effect
- increased free water excretion (ADH antagonism and ADH independent effects)
What clinical features are most discriminatory for cushing's syndrome?
striae (esp if purple, >1cm)
weight gain with decreasing growth velocity in children
What are the best screening tests for cushing's syndrome?
1. 24hr free urinary cortisol
2. 1mg overnight dexamethasone suppression
3. midnight salivary cortisol
What is the rationale of diagnosing cushing's syndrome?
1st exclude endogenous glucocorticoids
perform 24hrFUC, 1mg ODS, Midnight SC
exclude physiologic causes of hypercortisolism
repeat one of above tests or consider Dex-CRH
What are recommended tests for cushing's in certain populations?
pregnancy - recommend using UFC instead of dex
epilepsy - do not use dex testing as interaction with AEDs - recommend nonsuppressed midnight cortisol
renal failure - 1mg overnight DST instead of UFC
cyclic cushing syndrome - recommend UFC
adrenal incidentaloma - recommend use of 1mg DST or late night cortisol, vs UFC
What conditions are associated with hypercortisolism in absence of cushing's syndrome?
Some clinical features present:
Poorly controlled DM
Unlikely to have clinical features
Intense chronic exercise
CBG excess (increased serum, but not urine cortisol)
What is the next step following confirmation of cushing's syndrome?
Measurement of serum ACTH:
- 20 - ACTH dependent - pituitary vs ectopic source
10-20 - usually ACTH dependent
What are features of pituitary cushings vs ectopic ACTH?
better responsiveness to dynamic testing, but substantial overlap. MRI pituitary not reliable (basically useless)
BIPPS often necessary, unless MRI shows >6mm adenoma AND suppression with HDDST/increase in CRH.
10% ectopics are suppressed by HDDST
ACTH/Cortisol >30% in CD, but not in ectopics on CRH test.
What is the most likely cause of ectopic ACTH secretion?
bronchial carcinoid (40%)
What conditions produce low renin and high aldosterone?
- bilateral adrenal hyperplasia
- aldosterone producing adenoma (Conn)
- Familial hyperaldosteronism
- Pure aldo-producing carcinoma
What conditions produce high renin and alsoterone?
- renal artery stenosis
- diuretics (?surreptitious)
- renin secreting tumour
What conditions produce low renin and low aldosterone?
Apparent mineralocorticoid excess
- Exogenous mineralocorticoid
- cushing's syndrome (production of mineralocorticoid compounds)
- licorice (inhibits 11b-HSD2)
- CAH/11bHSD2 deficiency
- Liddle's syndrome (activating mutation of collecting tubule sodium channel)
What excess is associated with fluticasone and ritonavir?
high glucocorticoid but normal cortisol
What are clinical findings in primarly aldosteronism?
Hypokalemia +/- alkalosis (40%)
Hypokalemic Sx (fatigue, HA, arrhythmias, muscle weakness or cramping, paraesthesias, polyuria, impaired IGT) - 20%
What is the prevalence of various causes of primary aldosteronism?
bilateral idiopathic hyperplasia 60%
aldosterone producing adenoma 35%
Primary adrenal hyperplasia (unilat) 2%
Pure aldo producing adrenocortical carcinoma (
When should testing for primary aldosteronism be considered?
HTN and hypokalemia
adrenal incidentaloma and hypertension
onset of HTN160/100
whenever considering secondary hypertension
What should be initially tested in w/u of primary aldosteronism?
Plasma aldosterone concentration and plasma renin activity
Increased PAC and Decreased PRA or PRC
AND PAC/PRA ratio >=555 or >=20
Investigate for primary aldosteronism
What antihypertensives have minimal effects on ARR testing?
What medications should be avoided in ARR testing?
a2 agnoists (central)
K+ wasting diruetics
K+ sparing diuretics
What are the most frequent Sx in phaeochromocytoma?
Sustained HTN 50-60%
What precipitates phaeo crises?
drugs (B-blockers, opiods, TCAs)
When is genetic testing indicated in phaeo?
young, 50% have genetic cause
What genes should be tested in phaeo?
Extra-adrenal - SDHB
Adrenal - RET, VHL
Multiple - SDHD, VHL
Malignant - SDHB
What are features of tests for phaeo?
Plasma free metanephrines - Sn >95%, Sp 80-95%
Urinary fraction metanephrines - Sn >90%, Sp 80-95%
Urinary catecholamines - Sn 70-90%, Sp 70-95%
What are imaging featuers of phaeo?
often heterogenous, large HU>30
What are features of adrenal incidentalomas?
Common - up to 9% at autopsy, 4% of CT scans
25% increase in size on FU
40% of patients have mets to adrenals if cancer Hx
What are frequencies of adrenal mass aetiologies?
Nonfunctional adrenal adenoma 70%
Subclinical cushing syndrome 5-10%
Adrenocortical carcinoma 4.5%
What are features of adrenocortical adenomas?
Small, =50% washout of contrast at 10 minutes
Isointense on T2wI
what are indications for surgery in an incidental adrenal mass?
Size >6cm or imaging sugg of malgnancy
Increase in Size
Phaeochromocytoma - for surgery
Primary hyperaldosteronism - surgery if unilateral disease confirmed
Autonomous cortisol secretion - consider if comobidities present, or in case of clearly abnormal endocrine tests.
What are S+Sx suggestive of androgen deficiency in men?
Incomplete sexual development, eunchoidism, aspermia
Reduced sexual desire (libido), activity
Decreased spontaneous erections
Breast discomfort, gynaecomastia
Loss of body hair, less shaving
Very small/shrinking testis (
What conditions are associated with decreased SHBG?
What conditions are associated with increased SHBG?
hepatic cirrhosis and hepatitis
use of anticonvulsants
use of estrogens
What are causes of primary androgen deficiency?
- testicular damage: trauma, orchitis, CTX/RTX/Toxins, spironolactone, ketoconazole
- mut in androgen bioenzyme synthesis
- LH/FSH receptor mutations
- myotonic dystrophy
What are causes of secondary androgen deficiency?
structural - pituitary/hypopit tumour, surgery, rad, trauma, infitration (fe, sarcoid, histiocytosis)
genetic - kallman, idiopathic HH, LH/FSH beta subunit mutations
functiona - hyperprolactinaemia, morbid obesity, curshing's syndrome
partial/transient - acute illness, chronic disease (ESRD, COPD, HIV, T2DM) - drugs - GC, Opiods, GnRH agonist, anabolic steroids
What are the effects of adiposity on testosterone?
- increased visceral fat
- increased insulin resistance
- decrease SHBG
- decreased total testosterone
severe obesity (BMI >35)
- massive increase in fat mass
- increased aromatase
- increased oestradiol
- decreased LH
- decreased free and total T
What are causes of hypogonadotropic hypogonadism?
Macroadenoma = mass effect
Micro-prolactinoma - PRL inhibits gonadotrophins
What is the relevance of prolactin in hypogonadotropic hypogonadism?
if >5-10x ULN, almost always due to prolactinoma