Endocrine Diagnostics Flashcards
What are the 3 steps to diagnosing an endocrine issue?
- Right patient
- Right test
- Interpretation of the results
How are patients seen by endocrinologists?
Usually patients are referred by the GP, depending on whether the patient’s symptoms are indicative of an endocrine issue
How would an endocrinologist reply to a GP referral?
a) See the patient in the endocrinology clinic and take a history
b) See the patient in the endocrinology clinic and take a history and perform a physical examination
c) Arrange for the patient to have a ‘full set’ of endocrinology blood tests before you see them in clinic
B - because a test alone would not provide a diagnosis, so first meeting the patient to take their history and conduct examinations may indicate a condition, upon which a test can be performed to check for it
All tests must be interpreted in context
Examinations provide physical findings
Once the history taking and physical examination have taken place by the endocrinologist, what happens next?
a) Patient reassured there is nothing wrong, and discharged
b) Run some endocrine diagnostics
(What is pre-test probability?)
B - Must ask yourself, ‘what is the pre-test probability that the patient has the condition I’m thinking of?’
Pre-test probability = the probability of a patient having the disorder before a diagnostic test result is known
The test gives added information to the suspicions of the condition the patient has
How does an endocrinologist choose the right test for the patient? What are the factors that contribute?
Provides risk and worry to the patient, requires money, and how will the results of this test change the way the patient is managed
What are some of the options for the endocrine diagnostics?
- Blood tests
- Imaging - MRI, CT etc.
- Do both, blood tests and imaging
Which diagnostic option is normally taken by the endocrinologist?
What is a static blood test?
A - First, take the static blood test to understand the biochemistry of the patient first, as imaging often comes up with false positive i.e. find incidental lumps in the imaging that may not be anything
Static blood test = snap shot in time of hormone levels in the patient’s when the blood test was taken
When should the blood test be taken e.g. if the patient is in the clinic at 4pm?
a) Now - this afternoon
b) Come back first thing the next day
B - Many hormones have circadian rhythms, so hormones measured at the wrong time of the day = difficult to interpret results
Cortisol levels are highest in the morning - so measuring in the afternoon may show a low result, but it may be due to adrenal failure or to the circadian rhythm + time of day
What are some factors to take into account for static blood tests?
Pulsatility: Many hormones are secreted in pulses
A pulse: burst of hormone release from the gland
Transiently high levels of the hormone in the blood
In a patient whose adrenals are producing little or no cortisol
The pituitary secretes more ACTH to try to stimulate the failing adrenal glands
Therefore a patient with adrenal failure should have high ACTH levels
ACTH release is pulsatile
Blood test might be taken during a pulse
High ACTH on blood test results
Blood test might be taken after a pulse
Low ACTH on blood test result
What are the tests conducted when:
a) suspect the patient has too much hormone?
b) suspect the patient has too little hormone?
a) Suppression test - try supress that hormone production, postive result = hormone cannot be suppressed / levels remain high
b) Stimulation test - try to stimulate the production of that hormone from the gland, positive result = hormone cannot be produced / levels do not increase
What are dynamic blood tests?
What are the pros and cons?
Taking multiple blood tests, e.g. before and after stimulation / suppression
Shows bigger picture but, takes long time, logistics, safety of patient, interpretation errors, etc.
Which hormone stimulates cortisol production in the adrenals?
How is this used to measure cortisol levels in a patient?
ACTH
Synthesised ACTH injected into patient to stimulate adrenal glands to produce cortisol
How are the endocrine results interpretted?
Pre-test probability is supported by the blood tests, i.e. if they predicted a patient does not have the condition and the blood results confirm so, or if they predicted a patient does have the condition and the blood results confirm so
Or the pre-test probability and the results are not concordant
If the pre-test probability and the results are discordant, what happens next?
a) Go with the results, these are always more accurate than the history and examination
b) Ignore results, and do nothing further
c) Troubleshoot
C - look at patient and look to see if anything has changed / condition has progressed
Look at the pre-test probability again and interpret the result in this context
Look at the logistics of the test: wrong patient, time of day / pulsatility not taken into account, sample not handled properly e.g. haemolysed or hormone degradation in the lab, lab error
Repeat the test if things are still puzzling
