Aani CP: Endocrine Flashcards
Which test do you do for pituitary function?
Triple test
What are the components of the triple test for pituitary function?
- IV insulin 0.15 Units/kg
- GnRH (100mg)
- TRH (200mcg)
Contraindications to the triple test?
- Ischaemic heart disease (hypo will cause MI)
- Epilepsy (hypoglycaemia will cause fit)
- Untreated hypothryoid
At what level does glucose stimulate pituitary?
<2.2
What happens in the triple test?
Insulin causes glucose to drop and then adrenaline is released
Side effects of triple test?
Aggressive, palps, sweaty, convulsions
TRH - metallic taste, nausea
What happens if glucose goes too low in triple test?
Rescue them with 50ml 20% dextrose - wide bore green cannula already in place
What should happen in order to raise glucose levels in triple test?
ACTH and GH should rise –> cortisol and GH increase glucose release to normalise glucose levels.
Cortisol shouldl get to 170-500nmol/l
GH should get to 6mcg/l
These rise in response to insulin lowering blood glucose
How high should a normal person’s cortisol get in response to the triple test?
Over 500nmol/l
In response to the triple test, if someone’s TSH remains low, what is the underlying diagnosis?
Hyperthryroidism because it is suppressing the TSH despite the action of TRH
If someone has 6000 prolactin, what do they have?
Prolactinoma
Which hormones are raised in acromegaly?
GH and prolactin
How to test if someone has acromegaly (test with hormones)?
GTT. Giving glucose should lower GH to 0 or undetectable e.g <0.3mcg.
If it does not = GH excess
What does TRH do?
Increases TSH and prolactin
What does prolactin do?
Secretion of milk Inhibits GnRH (causing amenorrhoea)
Treatment of pituitary adenoma?
Depends if it is secreting hormones.
Prolactin secreting? Give dopamine agonists e.g. Bromocriptine/Cabergoline
GH secreting? Give octreotide (mimics somatostatin) /surgery/radiotherapy
Side effects of dopamine agonists?
Excess dopamine = think manic. Super powers, gambling etc.
What does the prolactin level need to be to diagnose a functioning pituitary adenoma?
> 5000
If large pituitary tumour does not have high prolactin, what is it?
Non-functioning pituitary adenoma
Why are the prolactin levels still high in a non-functioning pituitary adenoma?
Because it is pressing on the pituitary stalk so dopamine cannot be released and so dopamine cannot suppress prolactin. = Secondary Hyperprolactinaemia
Which antibodies are in Hashimotos?
Anto Thyroid Peroxidase (Anti-TPO)
Hypothyroid - Low T4, high TSH
Which antibodies are in Graves?
TRAbs - Thyrotropin Receptor Antibodies
What is the T4 and TSH of subclincial Hypothyroid?
Normal T4
High TSH
May also have TPO Abs (susceptible to getting Hashimotos)
Why might a pregnant lady have low TSH?
hCG acts like TSH and stimulates T4 release (especially if high HCG). This feeds back and reduces TSH release
Management of hypothyroid?
Levothyroxine 50–1250–200 mcg/day
Why is T4 low in sick euthryoid?
Illnesses causes thyroid to shut down to reduce metabolic rate. Low T4, normal or high TSH
Treatment of Hyperthyroid?
Depends on cause. Always give Beta Blockers. In low uptake hyper - treat symptoms In high uptake - give Radioactive Iodine. OR drugs OR surgery Thionamines: - Carbimazole - Propylthiouracil (PTU) - not used often because of aplastic anaemia risk
What investigation would be useful in high Thyroxine?
Technitium Scan (high uptake causes and low uptake causes)
Other symptoms of Graves?
- Thyroid acropachy
- Pretibial Myxodema
- Exophthalmos (because TSH receptors on back of eyes)
What causes high thyroixine in Graves?
TSH Receptor antibodies stimulate TSH release
What is thyroxine bound to in blood?
TBG (thyroid binding globulin)
Albumin
Side effect of Propylthiouracil (PTU)?
Aplastic Anaemia
What is the most common cause of hypothyroidism worldwide?
Iodine deficiency
What treatment is used for DeQuervains Viral Thyroiditis?
Beta Blockers and NSAIDs
2 markers for medullary thyroid carcinoma?
CEA and calcitonin
3 types of thyroid cancer?
Papillary - Most common
Follicular
Medullary - Least common (MEN2 Ass.)
Cells that medullary thyroid carcinoma originates in?
Parafollicular Cells
Generic tumour marker for thyroid cancer?
Thyroglobulin
Biochem of Conn’s?
Primary Hyperaldosteronism so HIGH Na and Low K
Where does the ACTH come from if it is Cushing’s DISEASE?
From BRAIN i.e. pituitary adenoma
Most common cause of Cushing’s Syndrome?
Steroid use (iatrogenic)
4 causes of Cushing’s Syndrome?
Endogenous (overproduction of cortisol) :
- Pituitary adenoma (Cushing’s Disease)
- Adrenal Adenoma (will have low ACTH)
- Ectopic ACTH secretion from another tumour e.g. Lung
Exogenous:
1. Steroid use
What is Low dose Dexamethasone Suppression test used for? How much do you give?
To see if someone has Cushings Syndrome. Give 0.5mg Dex every 6 hours for 48 hours. If cortisol is suppressed, you are NORMAL yey. If not, you have CUSHINGS SYNDROME do high dose Dex to determine cause.
What test distinguishes cushings disease and other causes?
High dose dexamethasone suppression test. 2mg every 6 hours for 48 hours.
If cortisol falls by 50% you have pituitary dependent cushings disease.
If cortisol is not supressed then it is an adrenal adenoma or ectopic ACTH from another source.
What might interfere with Dexamethasone Suppression test, leading to false positives?
Oestrogen
Phenytoin/Phenobarbitone - these drugs induce CYP3A4 which increases hepatic clearance of dexamethasone
What investigation do you do for Conn’s?
Aldosterone: Renin Ratio. Will be high because high Aldosterone suppresses Renin.
Management for Conn’s?
K sparing diuretics (spironolactone, amiloride)
What is Addison’s?
Primary adrenal insufficiency - adrenals do not make enough cortisol
Symptoms of Addison’s?
Skin pigmentation (due to high cleavage of POMC to make ACTH)
Hypotension (due to low cortisol)
Lethargy
Depression (cortisol is happy hormone)
Investigation for Addison’s?
SynthACTHen test. If Cortisol rises = you’re normal. If cortisol does not rise = Addison’s.
Management of Addison’s?
Hormone replacement therapy - corticosteroid replacement. Hydrocortisone/fludrocortisone
What is pheochromacytoma (caused by)
Adrenal medulla tumour secreting catecholamines i.e. adrenaline
Investigation for pheochromacytoma?
24 hour urinary catecholamine measurements and VMA and metanephrines
Treatment of pheochromacytoma?
Alpha Blockade THEN Beta Blockade THEN surgery to remove the tumour
Symptoms of Pheochromacytoma ?
Hypotension
Arrhythmias
Death
Why can you not give B blockers in Pheochromacytoma before A blockers?
If you give B blockers first, the heart contractility will reduce (good). But then in response, the vessels will constrict (alpha mediated) and you could get a hypertensive crisis. You don’t get vasodilation because the B mediated dilation is blocked by the beta blockers.
which 3 tests are done fir diabetes?
OGTT
Fasting Plasma Glucose
HBA1c
What is HbA1c in Diabetes mellitus?
HbA1c > 48
What is OGTT in T2DM?
> 11.1
What is Fasting Glucose in T2DM?
> 7.8
What levels show impaired glucose tolerance?
OGTT >78 but less than 11.1
Name the drug used for patients with type 2 diabetes which inhibits the enzyme alpha glucosidase in the brush border membrane of the small bowel.
Acarbose leaving undigested sugar in the bowel giving wind as a side effect
Acarbose leaving undigested sugar in the bowel giving wind as a side effect
Gliptins e.g. alogliptin
What is C-peptide?
It is cleaved from Pro-insulin. Pro insulin is cleaved into c-peptide and insulin
What does high levels of c-peptide in the blood indicate?
That endogenous insulin is being made
What are endogenous causes of high insulin?
Insulinoma (rare)
Islet cell hyperplasia
What do sulphonureas do?
Increase insulin from beta cells in pancreas
If glucose is low, insulin is low and c-peptide is low. What could be the cause?
When glucose is low. Body turns off insulin production so low C-peptide is normal. This could be caused by: fasting exercise illness anorexia hypo-pituitaty disorder
What are the expected blood results in a non-islet cell tumour ?
Low glucose Low insulin Low c-peptide Low ketones Low FFA (free fatty acids) The Big IGF-2 binds to IGF-1 receptors and insulin receptors acting like insulin