Endocrine and Metabolic Disturbance Flashcards
What is the difference between primary and secondary endocrine disease?
Primary - target organ dysfunction
Secondary - pituitary dysfunction
What are mineralocorticoids and where are they produced?
Function is to influence salt and water balance
Produced in the zona glomerulosa in the adrenal cortex.
eg. aldosterone
What are glucocorticoids and where are they produced?
Function is to reduce inflammation and suppress the immune system. Affect carbohydrate, lipid and protein metabolism.
Produced in the zone fasciculate in the adrenal cortex.
eg. cortisol
What are androgens and where are they produced?
Sex hormones, produced in the zona reticularis in the adrenal cortex (also in the reproductive organs)
eg. testosterone
What is produced in the adrenal medulla?
Epinephrine, norepinephrine and dopamine
What is Cushing’s syndrome?
Clinical state produced by chronic glucocorticoid excess and loss of the normal feedback mechanisms of the hypothalamo-pituitary-adrenal axis.
What causes Cushing’s syndrome?
Exogenous:
- Oral steroids
Endogenous:
- Adrenal tumour (benign/malignant - low ACTH)
- Pituitary tumour secreting ACTH (Cushing’s disease)
- Ectopic ACTH secreting tumours (SCLC, carcinoid)
What are the signs and symptoms of Cushing’s syndrome?
Central obesity (lemon on a stick), moon face, striae, plethora, buffalo hump, thin skin/hair/nails, hirsutism, acne, depression, bruising, DM
How is Cushing’s syndrome investigated primarily? (what is diagnostic)
- 24 hour urinary free cortisol excretion (levels >280) AND
- Overnight dexamethasone suppression test (no cortisol suppression as loss of feedback
- 48h dexamethasone suppression test (measure at 0 and 48h, failure to suppress cortisol)
Bloods may show hypokalaemic metabolic acidosis - this is because cortisol at high levels can simulate the effects of aldosterone > increased sodium > potassium excretion > bicarbonate resorption
How can you localise the cause of Cushing’s syndrome?
- Do plasma ACTH levels:
- Low ACTH = adrenal tumour (do CT/MRI)
- High ACTH = pituitary/ectopic tumour - Ectopic ACTH suspected - administer metyrapone (inhibits cortisol synthesis), if cortisol is still high the ACTH is coming from an ectopic source
- High dose dexamethasone test:
- <90% drop in urinary cortisol = ectopic ACTH
- >90% drop in urinary cortisol = pituitary adenoma (cushings disease) - Then do corticotrophin releasing test, cortisol will rise with pituitary disease but not ectopic.
What is Cushing’s disease?
Bilateral adrenal hyperplasia from an ACTH-secreting pituitary adenoma.
Plasma cortisol not suppressed on low dose dexamethasone test only high dose.
What can cause ectopic ACTH production? What are the specific features?
- Small cell lung cancer
- Carcinoid tumours (slow-growing, neuroendocrine)
Pigmentation, hypokalaemic metabolic acidosis, weight loss, hyperglycaemic. Tend to not have classical Cushing’s syndrome features.
Even high dose dexamethasone fails to suppress cortisol production.
Which adrenal tumours can cause Cushing’s syndrome?
- Adrenal adenoma/malignancy (no cortisol suppression in low/high dose)
- Adrenal nodular hyperplasia (as above)
How is Cushing’s disease managed?
MEDICAL (often adjunct to surgery)
- Somatostatin analogue (pasireotide)
- Steroidogenesis inhibitor (metyrapone)
SURGICAL
- Pituitary adenectomy
- Patients may need post-surgery steroid replacement to avoid adrenal crisis
How is ectopic ACTH managed?
MEDICAL (adjunct)
- Mifepristone
- Paseireotide
- Metyrapone
SURGICAL
- Resection or ablation of tumour
How is adrenal disease managed?
MEDICAL (adjunct)
- Mifepristone
- Paseirotide
- Metyrapone
SURGICAL
- Unilateral/bilateral adrenalectomy (depending on if tumour or hyperplasia)
- May need permanent steroid replacement
What causes hypoadrenalism?
Primary - Autoimmune destruction of adrenals aka Addison’s (glucocorticoid and mineralocorticoid deficiency)
Secondary - ACTH pituitary deficiency (only glucocorticoid deficiency as mineralocorticoids controlled by RAAS), usually due to long-term steroid use and withdrawal
What are the clinical features of hypoadrenalism?
Malaise, weight loss, nausea and vomiting, abdo pain, postural hypotension, hypoglycaemia, mood disturbance, adrenal crisis
‘Lean, tanned, tired, tearful’
How can you distinguish between primary and secondary causes of hypoadrenalism?
Do short syncathen test (synthetic form of ACTH) - measure baseline cortisol, give 250 micrograms IM syncathen and measure cortisol at 0,30,60 mins
Healthy - cortisol levels should double
Primary - subnormal response to ACTH as problem lies within adrenal gland
Secondary - dramatic increase in cortisol levels (>550NM/L) as problem lies within pituitary ACTH defieicney
What is Addison’s disease?
Autoimmune destruction of the adrenal cortex leading to mineralocorticoid and glucocorticoid deficiency. Always have at the back of your mind bc it is very non specific!
Symptoms may include:
- lethargy, weakness, weight loss, salt craving
- hyperpigmentation (as ACTH has same precursor molecule as melanocyte stimulating hormone)
- collapse/shock
What do investigations show in Addison’s disease?
- Low sodium, high potassium
- Low glucose
- High urea and calcium
- Anaemia
- High ACTH
- Positive 21-hydroxylase adrenal autoantibodies
How is Addison’s disease managed?
Steroid replacement with hydrocortisone and fludrocortisone
Must warn against abruptly stopping steroids as could precipitate an adrenal crisis - give steroid card! Double glucocorticoids if unwell, keep fludrocortisone the same
Follow up with BP, U&Es yearly
How is secondary adrenal insufficiency managed?
- Dont abruptly withdraw steroids!
- Replace glucorticoids with hydrocortisone
(nb there is no hyper pigmentation as ACTH is low)
What are the features of an adrenal crisis?
Hypovolaemic shock, abdo pain, vomiting, hypoglycaemia, confusion and fever
How is an adrenal crisis managed?
- 1 litre 0.9% saline STAT
- 100mg IV hydrocortisone STAT then 200mg/24hr
- Correct hypoglycaemia
Monitor BP, fluid status and electrolytes
What are the 3 ways in which aldosterone secretion is managed?
- RAAS - levels rise in response to low BP and renin release
- Potassium - directly stimulated aldosterone secretion
- ACTH - this is minor!!
What is primary hyperaldosteronism?
Excess production of aldosterone, independent of RAAS causing sodium and water retention (polydipsia/uria, hypertension, hypokalaemia)
What causes primary hyperaldosteronism?
- Solitary aldosterone-producing adenoma (Conns syndrome)
2. Bilateral adrenocortical hyperplasia
What are the characteristic bloods in primary hyperaldosteronism?
- Hypokalemia (but not always!)
- Hypomagnesia
- Metabolic alkalosis
- Aldosterone/renin ratio high
How is primary hyperaldosteronism managed?
Conn’s - laparoscopic adrenalectomy with post-op spironolactone
Hyperplasia - spironolactone, amiloride or eplenerone
Carcinoma - surgery and post-op adsrenolytic therapy with mitotane
What causes secondary hyperaldosteronism?
Any condition which increases renin production!! eg. renal artery stenosis, HF, liver failure, nephrotic syndrome Barrters syndrome Gitelmanns syndrome
What is Bartters syndrome?
Congenital (AR) salt wasting via a sodium and chloride leak in the loop of Henle due to a defective channel.
Presents with failure to thrive, polyuria, polydipsia. Normal BP!
Sodium loss leads to volume depletion causing increased renin and aldosterone production (low K, metabolic alkalosis)
How is Bartter’s syndrome managed?
- Potassium replacement
- NSAIDS and ACE-is
What is a phaeochromocytoma?
Tumour found in the adrenal medulla that produces CATECHOLAMINES (dopamine, norepinephrine, epinephrine)
Follow the 10% rule - 10% malignant, 10% extra-adrenal, 10% bilateral, 10% familial
Symptoms precipitated by exercise, stress, certain drugs
What are the symptoms of phaeochromocytoma?
Classical triad of:
- Episodic headache
- Sweating
- Tachycardia
Tend to have a very high BP!!!
Which cancer syndromes are phaeochromocytomas sometimes related to?
Thyroid
MEN2A,B
Neurofibromatosis
von Hippel-Landau syndrome
How is phaeochromocytoma investigated?
- Do plasma and 3x24h urinary test for met adrenaline and normetadrenaline (3x normal upper limit)
- Abdo CT/MRI or meta-iodobenzylguanidine scan to localise tumour
- Genetic testing to investigate cancer syndromes
How is phaeochromocytoma managed?
- Alpha/beta-blockers (ensure hydration and high salt diet after to avoid hypotension) eg. phenoxybenzamine then propranolol
- Surgical excision of tumour (if appropriate)
How is a hypertensive crisis managed?
Phentolamine IV (alpha blocker)
Must manage quickly as risk of cerebral haemorrhage, cardiac arrhythmias, MI, HF
What is the use of adrenal vein sampling?
Used to investigate hyperaldosteronism
If aldosterone levels are >3x higher in one vein than the other, indicates a unilateral adenoma that can be surgical excised
Which hormones does the anterior pituitary produce?
ACTH, TSH, FSH/LH, Prolactin, GH
Which hormones does the posterior pituitary produce?
ADH, oxytocin
What causes panhypopituitarism?
This is deficiency of all anterior hormones due to irradiation, surgery or tumour
What causes hypopituitarism at the level of the hypothalamus?
- Kallmans syndrome
- Tumour
- Inflammation
- Infection (TB, meningitis)
What is Kallmans syndrome?
Delayed/absent puberty and impaired sense of smell due to HYPOGONADOTROPHIC HYPOGONADISM
This is X-linked recessive and caused by ANOS1 gene mutations
What causes hypopituitarism at the level of the pituitary stalk?
- Trauma
- Surgery
- Mass lesion eg. craniopharygioma
- Meningioma
- Carotid artery aneurysm
What causes hypopituitarism at the level of the pituitary?
- Tumour
- Irradiation
- Inflammation
- Autoimmunity
- Infiltration (haemochromatosis, amyloid, mets)
- Ischaemia (pituitary apoplexy, sheehan’s syndrome, DIC)
What is pituitary apoplexy?
Infarction/haemorrhage of the anterior pituitary (usually due to tumour) causing headache, collapse, visual loss (bitemporal quadrantopia) and death.
How is pituitary apoplexy diagnosed and managed?
Diagnose with MRI and blood tests
If severely unwell requires surgery. If milder, urgent IV steroids and fluid balance
What are the symptoms of hypopituitarism?
Depends on whichever hormone is lacking:
- GH - obesity, dry, low strength, osteoporosis
- FSH/LH - no menses, los of fertility, erectile dysfunction, low libido, hair changes
- Thyroid - think hypothyroidism
- ACTH - adrenal insufficiency but no pigmentation!
- Prolactin - rare, absent lactation
How is hypopituitarism investigated?
BLOODS - LH, FSH, testosterone, oestrogen, prolactin, IGF-1, U&E, FBC
SPECIAL - short synacthen, insulin tolerance test, growth hormone tests
IMAGING - MRI to look for lesion
How is hypopituitarism managed?
- TREAT UNDERLYING CAUSE
2. REPLACE DEFICIENT HORMONES
What is Sheehan’s syndrome?
Postpartum pituitary gland necrosis - caused by blood loss and hypovolaemic shock during and after childbirth
Classic early symptoms are agalactorrhoea, hypothyroidism and amenorrhea
If severe can see pituitary halo ring sign on CT/MRI (halo around empty sella turtica)
What can cause a raised prolactin?
the p’s:
pregnancy
prolactinoma
physiological
PCOS
primary hyperthyroidism
phenothiazine, metoclopramide, domperidone
Presents as impotence, loss of libido, amenorrhoea, galactorrhoea
How is prolactin quantified?
Raised prolactin = PRL>390mU/L
If >5000 likely to be a prolactinoma
What are the symptoms of hyperprolactinaemia?
Females: amenorrhoea, infertility, galactorrhea, loss of libido, weight gain, dry vagina
Males (present later): ED, loss of hair, glacrotthoea, osteoporosis