Endocrine Flashcards
What is adrenal insufficiency?
the adrenal glands do not produce enough steroid hormones, particularly cortisol and aldosterone.
Steroids are essential for life = life-threatening unless the hormones are replaced.
What is Addison’s disease?
PRIMARY ADRENAL INSUFFICIENCY
specific condition where the adrenal glands have been damaged, resulting in a reduction in the secretion of cortisol and aldosterone
Most common cause of Addison’s disease
autoimmune
what is secondary adrenal insufficiency?
inadequate ACTH stimulating the adrenal glands, resulting in low cortisol release
What is ACTH
Adrenocorticotrophic hormone
secreted by the pituitary gland
causes of secondary adrenal insufficiency
damage to pituitary gland:
- pituitary tumour
- infection
- loss of blood flow
- radiotherapy
- Sheehan’s syndrome = massive blood loss in childbirth that leads to necrosis of the pituitary gland
what is tertiary adrenal insufficiency?
inadequate CRH release by the hypothalamus
what is CRH
Corticotrophin releasing hormone, released by the hypothalamus
Describe the HPA axis
hypothalamic-pituitary-adrenal axis:
- hypothalamus releases corticotrophin releasing hormone
- causing anterior pituitary to release adrenocorticotrophic hormone
- causing the adrenal cortex in the adrenal glands to release cortisol
causes of tertiary adrenal insufficiency
long term oral steroids - suppress the hypothalamus
This is why you shouldn’t suddenly withdraw exogenous steroids - hypothalamus is suppressed so no endogenous steroids will be produced
symptoms of adrenal insufficiency
Fatigue Nausea Cramps Abdominal pain Reduced libido
Signs of adrenal insufficiency
Bronze hyperpigmentation to skin (ACTH stimulates melanocytes to produce melanin)
Hypotension (particularly postural hypotension)
Ix for adrenal insufficiency
Hyponatraemia
Hyperkalaemia
Early morning cortisol - often falsely normal
Short synacthen test = FOR DIAGNOSIS
ACTH
- High in primary adrenal insufficiency
- low in secondary adrenal insufficiency
Adrenal cortex antibodies & 21-hydroxylase antibodies - in autoimmune adrenal insufficiency
CT/MRI adrenals
MRI pituitary
What is the short synacthen test?
For diagnosing adrenal insufficiency
Give synacthen (synthetic ACTH) blood cortisol measured at baseline, 30 mins and 60 mins Synthetic ATCH wil stimulate healthy adrenal glands & the cortisol should at least double
Failure of cortisol to at least double = primary adrenal insufficiency (Addison’s)
tx of adrenal insuffiency
hydrocortisone to replace cortisol
fludrocortisone to replace adolesterone
Patients need: steroid card & double doses on sick days (don’t STOP)
What is an addisonian crisis?
Adrenal crisis
Acute presentation of severe Addison’s disease
The absence of steroid hormones leads to a life threatening presentation
Symptoms of addisonian crisis
Reduced consciousness
Hypotension
Hypoglycaemia, hyponatraemia, hyperkaemia
Patients can be very unwell
what triggers an addisonian crisis
infection
trauma
other acute illness
sudden steroid withdrawal
mx of addisonian crisis
Intensive monitoring IV hydrocortisone IV fluid resuscitation Correct hypoglycaemia Careful monitoring of electrolytes
What is cushings syndrome?
the signs and symptoms that develop after prolonged abnormal elevation of cortisol.
What is Cushings disease?
the specific condition where a pituitary adenoma (tumour) secretes excessive ACTH.
Difference between cushings syndrome and cushings disease
Cushings disease causes cushings syndrome
but cushings syndrome isn’t always caused by cushings disease
symptoms of cushings syndrome
round 'moon' face central obesity abdo striae buffalo hump - fat pad on upper back proximal limb muscle wasting
HTN cardiac hypertrophy hyperglycaemia (T2DM) depression insomnia
osteoporosis
easy bruising
poor skin healing
causes of cushings syndrome
exogenous steroids
cushings disease = pituitary adenoma releasing excessive ACTH
adrenal adenoma
paraneoplastic cushings - ACTH released from small cell lung cancer
ix for cushings syndrome
dexamtheasone suppression test 24 hour urinary free cortisol FBC - raised WCC U&E - hypokalaemia if aldosterone also secreted by adrenal adenoma MRI brain - pituitary adenoma chest CT - SCLC Abdo CT - adrenal tumour
Tx for cushings syndrome
remove underlying cause
- trans-sphenoidal removal of pituitary adenoma (cushings disease)
- surgical removal of adrenal tumour
- surgical removal of tumours producing ectopic ACTH
If you can’t remove the cause - remove the adrenal glands and give replacement steroids for life
what is the dexamethasone suppression test used for?
used to diagnose cushings syndrome and find the cause
- Give dexamethasone at 10pm at night, measure cortisol and ACTH in the morning
- do low dose test first - give 1mg of dexamethasone = used to see if they have a normal HPA axis or if they have cushings syndrome
- do high dose test second if they have an abnormal low dose test to look for the cause of cushings syndrome
how does the low dose dexamethasone test work and what is a normal result/a result showing cushings syndrome?
Give 1mg dexamethasone at 10pm
In the morning measure cortisol and ACTH
In a normal person, the addition of steroids causes negative feedback on the hypothalamus and pituitary = low cortisol and ACTH in the morning
In someone with cushings syndrome, the addition of a small amount of steroids makes no difference as they already have high levels of cortisol. Therefore cortisol will be high/normal in the morning
how does the high dose dexamethasone test work and what do the results show?
high dose test is performed following an abnormal result on the low dose test
give 8mg of dexamethasone at 10pm, measure the cortisol and ACTH the next morning
In cushings disease (pituitary adenoma) = pituitary shows some response to negative feedback. 8mg of dex is enough to suppress cortisol & ACTH
In adrenal adenoma = cortisol production is independent on the pituitary. So cortisol is not suppressed but ACTH is
Ectopic ACTH production (SCLC) = cortisol and ACTh won’t be suppressed because ACTH production is independent of the hypothalamus and pituitary gland
What is diabetes insipidus?
a lack of ADH or lack of response to ADH = prevents the kidneys from concentrating the urine so there’s polyuria and polydipsia
how can diabetes insipidus be classified?
nephrogenic
cranial
what is nephrogenic diabetes insipidus?
when the collecting ducts of the kidneys do not respond to ADH
causes of nephrogenic diabetes insipidus
- lithium
- mutations in AVPR2 gene on X chromsome
- Intrinsic kidney disease
- Hypokalaemia
- Hypercalcaemia
what is cranial diabetes insipidus?
when the hypothalamus does not produce ADH for the pituitary gland to secrete
Causes of cranial diabetes insipidus
idiopathic brain tumours head injury brain malformations brain infections - meningitis, encephalitis, TB Brain surgery/chemotherapy
presentation of diabetes insipidus
Polyuria polydipsia dehydration postural hypotension HYPERNATRAEMIA
ix for diabetes insipidus
low urine osmolality
high serum osmolality
water deprivation test
what is the water deprivation test and how is it done?
used to diagnose diabetes insipidus
1) no fluids for 8 hours = fluid deprivation
2) measure urine osmolality
3) give synthetic ADH (desmopressin)
4) 8 hours later measure urine osmolality again
What do the results of the water deprivation test show?
For cranial diabetes insipidus = urine osmolality starts low as the brain isn’t producing any ADH, then after giving desmopressin the usine osmolality is high because the kidneys can still respond to ADH
For nephrogenic diabetes insipidus = the urine osmolality is low to start and stays low after desmopressin is given as the kidneys can’t respond to ADH
for primary polydipsia = the 8 hours of water deprivation will cause a high urine osmolality even before desmopressin is given
whats another name for the water deprivation test?
desmopressin stimulation test
management of diabetes insipidus
desmopressin in cranial DI
High doses of desmopressin in nephrogenic DI under close monitoring
what are the short synacthen test, dexamethasone suppression test and water deprivation test/desmopressin stimulation test each used for?
short synacthen test = low cortisol/adrenal insufficiency ie Addisons disease
dexamethasone suppression test = high cortisol ie cushings syndrome/disease
water deprivation test = diabetes insipidus (nephrogenic/cranial)
Symptoms/signs of Hypercalcaemia
‘bones, stones, groans and psychic moans’
- abnormal bone remodelling/fracture risk
- kidney stones
- abdo cramps/nausea/ileus/constipation
- lethargy, depression, psychosis
corneal calcification
shortened QT interval on ECG
hypertension
causes of Hypercalcaemia
1) primary hyperparathyroidism (most common in the community)
2) malignancy (most common in hospital) = SCLC, bone mets, myeloma
Other causes: sarcoidosis vitamin D intoxication acromegaly thyrotoxicosis thiazides dehydration Addisons disease
mx for Hypercalcaemia
rehydration with NaCl - 3-4L /day
after rehydration = bisphosphonates (take 2-3 days to work)
calcitonin is quicker than bisphosphonates
steroids in sarcoidosis
symptoms of hypocalcaemia
NEUROMUSCULAR EXCITABILITY
tetany - muscle twitching, cramping and spasm
perioral paraesthesia
chronic hypocalcaemia = depression, cataracts
ECG = prolonged QT interval
Trousseau’s sign
Chvosteks sign
what is trousseau’s sign?
seen in hypocalcaemia
carpal spasm if the brachial artery occulded by inflating BP cuff to a pressure above their systolic BP
what is chvostek’s sign?
seen in hypocalcaemia
tapping over parotid causes facial muscles to twitch
causes of hypocalcaemia
vitamin D deficiency (osteomalacia) CKD hypoparathyroidism pseudohypoparathyroidism rhabdomyolysis magnesium deficiency massive blood transfusion acute pancreatitis
contamination of blood samples with EDTA = falsely low calcium
mx of hypocalcaemia
IV replacement for severe hypocalcaemia - IV calcium gluconate 10ml of 10% solution over 10 mins
ECG monitoring
ECG changes seen in hyperkalaemia
Tall tented T waves
Small/loss of P waves
Widened QRS complex - leads to sinusoidal pattern
Asystole
Causes of hyperkalaemia
AKI Potassium sparing diuretics ACEi ARBs Spironolactone Ciclosporin Heparin Metabolic acidosis Addison's disease (primary adrenal insufficiency) Rhabdomyolysis Massive blood transfusion
Mx of hyperkalaemia
Stabilise cardiac membrane = IV CALCIUM GLUCONATE (this doesn’t lower serum K)
Short term shift of K from extracellular to intracellular space = INSULIN/DEXTROSE INFUSION & NEB SALBUTAMOL
Removal of K from body = CALCIUM RESONIUM (oral/enema), LOOP DIURETICS, DIALYSIS (haemofiltration/haemodialysis for patients with AKI & persistent hyperkalaemia)
Stop any exacerbating drugs
Treat underlying cause
classification of hyperkalaemia
mild = 5.5 to 5.9 moderate = 6.0 to 6.4 severe = >6.5
how should you classify hypokalaemia?
with or without hypertension
causes of hypokalaemia with hypertension
cushings syndrome
conn’s syndrome (primary hyperaldosteronism)
liddle’s syndrome
11-beta hydroxyls deficiency - congenital adrenal hyperplasia
causes of hypokalaemia without hypertension
diuretics GI loss - diarrhoea and vomiting renal tubular acidosis bartter's syndrome - inherited cause of severe hypokalaemia gitelman syndrome
symptoms of hypokalaemia
muscle weakness
hypotonia
predisposes to digoxin toxicity
ECG changes in hypokalaemia
U waves
small/absent t waves
prolonged PR interval
ST depression
causes of hypokalaemia with alkalosis
vomiting
thiazide and loop diuretics
cushings syndrome
conn’s syndrome (primary hyperaldosteronism)
causes of hypokalaemia with acidosis
diarrhoea
renal tubular acidosis
acetazolamide
partially treated DKA
mx of hypokalaemia
Check and replete Magnesium
Treat underlying cause
mild = oral KCl if no acidosis or ora potassium bicarbonate if there’s acidosis
moderate = oral KCl unless can’t have PO or there’s ECG changes
Severe = IV KCl. Do not give more than 20mmol/hr. concentration should not exceed 40mmol/L. Faster transfusion than 20mmol/hr through a central line in ICU. Need continuous cardiac monitoring and check K levels every 2-4 hrs
what are the causes of hyponatraemia?
URINARY SODIUM >20 MMOL/L
- thiazide / loop diuretics
- addison’s disease
- diuretic stage of renal failure
- SIADH
- hypothyroidism
URINARY SODIUM <20 MMOL/L
- diarrhoea
- vomiting
- sweating
- burns
- adenoma of rectum
- HF
- liver cirrhosis
- nephrotic syndrome
- IV dextrose
- psychogenic polydipsia
complication of untreated hyponatraemia
cerebral oedema = brain herniation
symptoms of hyponatraemia
early = headache, lethargy, nausea, vomiting, dizziness, confusion, muscle cramps
late = seizures, coma, respiratory arrest
causes of hyponatraemia by volume status
hypovolemic hyponatraemia/clinically dehydrated: diuretic stage of renal failure, diuretics, Addisonian crisis
euvolemic hyponatraemia: SIADH
heart failure, liver failure, nephrotic syndrome
mx of hyponatraemia
hypovolaemic cause:
- 0.9% NaCl
euvolemic cause:
fluid restrict to 500-1000ml/day.
consider demeclocycline / vaptans
hypervolemic cause:
fluid restrict to 500-1000ml/day.
consider loop diuretic/vaptans
severe hyponatraemia with symptoms (<120mmol/L): HDU & give hypertonic saline (3% NaCl)
complications of mx of hyponatraemia
central pontine myelinolysis (osmotic demyelination syndrome)
don’t correct Na by more than 6-12 mmol/l in a 24 hour period
symptoms = dysarthria, dysphagia, paraparesis or quadriparesis, seizures, confusion, and coma
(locked in syndrome)
causes of hypernatraemia
dehydration
osmotic diuresis e.g. hyperosmolar non-ketotic diabetic coma
diabetes insipidus
excess IV saline
mx of hypernatraemia
a rate of no greater than 0.5 mmol/hour correction is appropriate = helps avoid cerebral oedema (seizures, coma and death)
IV 5% dextrose
causes of hyperlipidaemia
Predominantly hypertriglyceridaemia = diabetes mellitus (types 1 and 2) obesity alcohol chronic renal failure drugs: thiazides, non-selective beta-blockers, unopposed oestrogen liver disease
predominantly hypercholesterolaemia = nephrotic syndrome cholestasis hypothyroidism familial hypercholesterolaemia
mx of hyperlipidaemia
for primary prevention:
- give to people with 10 year cardiovascular risk of >10% OR T1DM OR eGFR <60
ATROVASTATIN 20MG OD
(titrate up to 80mg if reduction in non-HDL cholesterol hasn’t fallen by at least 40%)
for secondary prevention:
- give if known IHD OR CVA OR PAD
ATROVASTATIN 80MG OD
How to assess 10 year cardiovascular risk
QRISK2
- age
- gender
- ethnicity
- postcode
- BMI
- smoker
- family hx CAD
- HTN, ?treated
- total cholesterol:HDL cholesterol
- DM
- AF
- Renal disease
- RA
lifestyle advice for hyperlipidaemia
cardioprotective diet - reduce fats, wholegrain starches, 5 portion fruit/veg, 2 portions fish per week, 4-5 portions unsalted nuts/seeds/legumes per week
physical activity - 150 mins cardio per week
weight management
alcohol intake to <14 units per week
smoking cessation
what secretes parathyroid hormone and what is it secreted in response to?
chief cells in the parathyroid glands
PTH secreted in response to hypoclacaemia
What does PTH do?
Increases serum calcium by -
- increasing osteoclast activity
- increasing calcium absorption from gut
- increasing calcium absorption from kidneys
- increasing vitamin D activity = increases calcium absorption from intestines
symptoms of hyperparathyroidism
symptoms of hypercalcaemia = painful bones, kidney stones, abdominal groans and psychiatric moans
causes of primary hyperparathyroidism
tumour of the parathyroid glands = releases uncontrolled amounts of PTH
High PTH & high calcium