INVESTIGATIONS - endocrine Flashcards
What should you check in someone presenting with hypercalcaemia?
PTH
In someone with hypercalcaemia, low PTH, low albumin and low Cl-, what should you be worried about?
What tests might you do?
Malignancy
Consider x-ray, CT, MRI or isotope bone scan
Investigation of choice for suspected adrenal insufficiency?
What would the results be?
Short synacthhen test
i.e. measure plasma cortisol levels 30 minutes before and after ACTH injection. In a healthy person, cortisol levels will increase from 250nmol/l to >550.
In someone with adrenal insufficiency, cortisol will be <500 even after ACTH injection.
What test can be used to differentiate between primary (adrenal), secondary (pituitary) and tertiary (hypothalamic) adrenal insufficiency?
Serum ACTH
Elevated ACTH = Addison’s / primary disease
Normal or low suggests a pituitary or hypothalamic problem.
What will renin and aldosterone levels be in Addison’s disease?
Renin is elevated (to compensate for no aldosterone synthesis in the adrenal cortex)
Aldosterone is suppressed due to non-functioning adrenal cortex (may help to differentiate Addison’s from secondary adrenal insufficiency)
Which antibodies may be present in Addison’s disease?
Anti-adrenal autoantibodies
21-hydroxylase antibodies
First line test for diagnosing Cushings?
What would the results of this test be?
Overnight dexamethasone suppression test
Healthy person: dexamethasone will trigger negative feedback response resulting in low ACTH and cortisol levels. In Cushing’s there is no such suppression.
If the pituitary is the cause of Cushing’s syndrome, what with ACTH levels be?
What would ACTH levels be if the adrenal gland was the cause?
High ACTH = pituitary cause or ectopic ACTH production
Low ACTH = adrenal cause (cortisol release is indpendent of ACTH levels)
When is cortisol usually highest, and when is it lowest?
Highest first thing in the morning
Lowest at night
Gold standard test for diagnosing pituitary adenoma?
Insulin stress test
Healthy person: It will create an acute hypoglycaemic state, so should trigger cortisol and GH.
If prolactin levels are raised, what imaging might you undertake?
MRI to look for pituitary tumour
What test is used to diagnose acromegaly?
Glucose tolerance test
(measure growth hormone after glucose is given; GH will be suppressed in a healthy person to <0.4ug/L, but won’t be suppressed in someone with acromegaly)
Can also measure IGF1 which will be elevated (note: IGF1 doesn’t fluctuate much throughout the day)
What test is used to confirm diabetes insipidus?
Water deprivation test
In diabetes insipidus what will urine osmolarity be?
And what about serum osmolarity?
Low urine osmolarity
High serum osmolarity
What investigation may be useful in the diagnosis of Conn’s? Why is this hard to carry out?
Aldosterone : renin ratio
High aldosterone, low renin (due to feedback from aldosterone)
If the R:A ratio is raised, investigate further with saline suppression test.
Patients tend to be on hypertensive medication which alters RAAS making results unreliable.
Which enzyme is usually deficient in congenital adrenal hyperplasia?
21 hydroxylase deficiency
What test should be carried out in cases of suspected CAH?
Measure 17 OH progesterone levels. Usually elevated in CAH.
Also do genetic analysis
What is calcitonin used as a marker for?
Medullary thyroid cancer (cancer of the parafollicular C cells)
Which differentiated thyroid cancer spreads via lymphatics? Which one is blood?
Papillary is lymphatics
Follicular is blood
Which antibodies may be present in Hashimoto’s thyroiditis?
anti-TPO
thyroid peroxidase
Why does medullary thyroid cancer result in hypocalcaemia?
Parafollicular c cells release calcitonin, which lowers calcium levels
Which antibodies would increase your suspicion of Graves disease being the diagnosis?
TSH receptor antibody
What’s the main risk factor for thyroid cancer?
Radiation
What grading on ultrasound of a thyroid nodule would warrant FNA?
U3 with worrying signs, or U4 or U5 should all undergo FNA
Which type of thyroid cancer cannot be diagnosed on FNA? WHy is this?
Follicular
Diagnosis requires thyroid lobectomy to assess extent of capsular invasion
What is AMES? What does it constitute and what’s it used for?
Age
Metastasis
Extent of primary tumour
Size of primary tumour
Used post-op to stratify patients as low risk or high risk
Low risk: young patients with no evidence of mets.
High risk: 40+ (men) or 50+ (women), with invasion / mets, or primary timour >5cm
What’s the prognosis for AMES high risk?
What about for low risk?
High risk: 61% 20 year survival
Low risk: 99% 20 year survival
What are U1, U2, U3, U4 and U5?
Ultrasound assessment of thyroid lumps U1 = normal U2 = benign U3 = indeterminate U4 = suspicious U5 = malignant
Investigations for toxic multinodular goitre?
TSH (should be suppressed)
Free T4 (elevated)
Iodine uptake scan - multiple hot and cold areas
CT may be indicated if signs of neck compression
What level of fasting plasma glucose is diagnostic of diabetes?
> 7 mmol/l
What level of plasma glucose is diagnostic of diabetes following an oral glucose tolerance test?
> 11.1 mmol/l two hours after 75g oral glucose load
What constitutes impaired glucose tolerance in the context of an oral GGT?
Plasma glucose of 7-11 mmol/l after 2 hours
What are glucose levels in hypoglycaemia?
<4 mmol/l
What’s the criteria for random plasma glucose to give a diagnosis of diabetes?
> 11.1 on repeat testing, or with symptoms
What’s the normal HbA1c in a healthy individual?
<41 mmol
What’s the target HbA1c for most diabetics?
48-58 mmol
What does HbA1c measure? What is it an indicator of?
Measures glycated haemoglobin
Indicator of blood glucose control over 2-3 months
What’s the difference between bicarbonate levels in DKA and HHS?
In DKA, bicarb is low
It’s high in HHS
Which ketones should you measure in the urine?
Which ketones should you measure in the blood?
Urine: acetoacetate
Blood: beta hydroxybutyrate
What should be used to screen for diabetic kidney disease?
ACR
Albumin creatinine ratio
Give some reasons for microalbuminuria false positives
Pregnancy
UTI
Vaginal discharge
What’s the blood pressure target for diabetics?
<130 / 80
What constitutes MILD background diabetic retinopathy (R1)?
What’s the appropriate next step?
Dot and blot haemorrhages Microaneurysms Hard exudates Cotton wool spots (ischaemia) Flame haemorrhages
Reassess in 12 months
What constitutes OBSERVABLE background diabetic retinopathy (R2)?
What’s the appropriate next step?
4 or more blot haemorrhages in one hemi field only
Reassess in 6 months (or refer to ophthalmology)
What constitutes referable background diabetic retinopathy (R3)?
Any of the following:
- 4 or more blot haemorrhages in both inferior and superior hemi fields
- venous bleeding
- intra-retinal microvascular abnormalities
What constitutes proliferative diabetic retinopathy (R4)?
Active new vessels or vitreous haemorrhage
Refer and treat (e.g. laser therapy)
First line test in secondary amenorrhoea?
Pregnancy test (human chorionic gonadotropin, hCG)
What is primary and secondary hypogonadism in females?
Primary = problem with ovaries Secondary = problem with hypothalamus or pituitary
WHO classifies ovulatary disorders as Group I, II and III.
What is each of these groups and how would you investigate each one?
Group I: hypothalamic pituitary failure
- progesterone challenge test (negative - oestrogen deficiency)
Group II: hypothalamic pituitary dysfunction
- progesterone challenge test (positive - normal oestrogen)
- e.g. PCOS
Group III: ovarian failure / hypergonadotrophic hypogonadism.
- measure TSH / LH (will be raised, but low oestrogen)
What’s progesterone challenge testing?
Give progesterone. If period follows it indicates normal oestrogen levels (= positive, as with group II ovulation disorders).
If period doesn’t follow 5 days of progesterone, oestrogen levels are low (negative result, as with group I and III)
What group of ovulatary disorder is suggested by LOW FSH and LOW LH?
Group I (pituitary / hypothalamic failure)
Results of low oestradiol, and low / normal FSH and LH are suggestive of what?
Secondary hypothalamic amenorrhoea
i.e. hypogonadism due to pituitary or hypothalmic problems
What 2 `things would you look for in terms of ovarian morphology on ultrasound in PCOS?
Increased ovarian volume (>10ml)
> 12 follicles between 2 and 8mm in diameter
What are LH levels in PCOS?
High
raised LH : FSH ratio
What are testosterone levels usually in PCOS?
High
What would gonadotrophin levels be in primary ovarian failure?
High (FSH and LH)
What would oestrogen levels be in primary ovarian failure?
Low
In men with hypogonadism (and therefore low testosterone), what would LH and FSH levels be in
a) primary hypogonadism
b) secondary hypogonadism
a) primary = High FSH and LH
b) secondary = pituitary or hypothalmic problems, so low LH / FSH
What would testosterone and FSH / LH levels be in Kleinfelters?
(47 XXY)
Low testosterone
High FSH / LH
elevtaed SHBG (sex hormone binding globulin)
What would testosterone and FSH / LH levels be in Kallman’s?
Low testosterone (results in delayed or absent puberty - due to loss of GnRH secretion)
What measurement can be taken to confirm ovulation?
Mid-cycle LH (day 21)
