Flashcards in Lecture 2 - Investigation of endocrine disease Deck (27):
What are the 3 types of hormone?
Peptide - PCTH, TSH
Steroid - Testosterone, oestradiol, cortisol
Thyroid Based Hormone TSH, T3, T4
What hormone does the thymus secrete?
Thymosin - Incr T cell production
What hormone does the GI tract secrete?
Grelin. Regulates hunger
What hormone does the heart secrete?
BNP - response to stress
Give a generic overview of the feedback regulation system
Hypothalamus signals to anterior pituitary
Anterior pituitary releases stimulated hormone to endocrine organ
Endocrine organ releases hormone.
Hormone negatively feedback to anterior pituitary + hypothalamus, switching them off
Describe the Hypothalamic-Pituitary-Adrenal axis
o Stress stimulus in amygdala hypothalamus produces CRF
o CRF acts on pituitary gland ACTH released into blood
o ACTH acts on adrenal glands cortisol released stress response
o Cortisol negative feedbacks to pituitary, hypothalamus + amygdala to stop stimulation to produce cortisol
What's the difference between a primary and secondary endocrine problem?
Primary - problem with the gland itself
Secondary - problem with the pituitary
What are the 2 causes of excessive cortisol production?
Primary problem - adrenal gland overproduces cortisol.
Test - low ACTH, high cortisol
Secondary problem - pituitary overstimulating adrenal glands
Test - high ACTH, high cortisol
What else could cause overproduction of cortisol?
Ectopic ACTH - could be caused by tumours of the:
Islet cell tumour in pancreas
Tumours of the thymus gland
What are the 2 causes of insufficient cortisol production?
Primary - hypothalamus is fine but adrenal gland not responding.
Test - High ACTH, low cortisol
Secondary - pituitary not producing ACTH, so low cortisol
What could cause secondary cortisol insufficiency
Taking steroids - bc blood cortisol is always high, body stops producing ACTH. When you stop taking steroids, body loses ability to regulate
Test for Cushing's (e.g. hypercortisol)
Suppression test - give dexamethasone (steroid - should suppress ACTH)
If steroid doesn't suppress ACTH, it tells you you have too much, but doesn't tell you if its a primary or secondary problem
Measure ACTH levels on day 1. Give dexamethasone and check ACTH levels on day 2 at 9am. If not less than <50nmol/L
Test for Addison's (hypocortisol)
Stimulation test - synacthen test. Give ACTH, should cause incr in cortisol.
Measure at 9am
Hypothyroidism - what would the test results be for primary/ secondary hypothyroidism
Primary - TSH high, T3/4 low
Secondary - TSH low, T3/4 low
Hyperthyroidism - what would the test results be for primary/ secondary hyperthyroidism
Primary - low TSH, high T3/4
Secondary - high TSH, high T3/4
What is euthyroid disease?
People don’t have thyroid disease, but have shock, inflammation, infection + cytokine production. Inflammation response.
Cytokines act on hypothalamus – prevents iodine uptake into thyroid cells
Prevents thyroperoxidase activity which makes thyroid hormones
Test for euthyroid?
Low T4/3, no TSH
What effects hormonal release?
Annual cycles – hair growth
Monthly cycles – menses
Diurnal – cortisol
Rapid amplitude cycles – insulin
Stress related – anterior pituitary hormones
Stimulus related – insulin
When should you take a urine sample?
When you have pulsatile secretion (peaks and troughs in secretion)
Analysis fo unstable hormones that break down in the blood
When you want to avoid venipuncture
What to look for in pheochromocytoma urine test?
Measure metanephrine + normetanephrine in urine (what catecholamines get broken down into)
Clinical features of phaeochromocytoma
Follow up test for phaeochromocytoma
Clonidine suppression test
What is an insulinoma + what is it's presentation?
Tumour of the pancreas
Secretes excess insulin
Presents as hypoglycaemic symptoms
Test for insulinoma?
Give IV insulin + measure C-peptide.
Exogenous insulin suppresses C-peptide, but it won’t in an insulinoma.
Signs and Symptoms of hypoglycaemia
Depression/ diaphoresis (sweating
Measuring thyroid in the blood
Free hormones are functional
When bound to TBG - inactivated
Immunoassay - take blood test to see how much free t3/4 there is