ENDO Flashcards
Describe the process of cortisol release
1 - hypothalamus releases CRH (corticotrophin release hormone)
2- anterior pituitary releases ACTH (adrenocorticotrophic hormone)
3 - adrenal gland releases cortisol
How is adrenal insufficiency diagnosed?
Short synacthen test
- administer synthetic ACTH which should induce cortisol rise
- failure of ACTH to rise = Addison’s
How would levels of ACTH differ in primary and secondary adrenal insufficiency?
Primary = high levels (problem is with adrenal glands)
Secondary = low levels (problem with pituitary)
What is Cushing’s disease?
Pituitary adenoma that secretes excessive ACTH
Give 4 causes of Cushing’s syndrome
1- long term steroids
2 - Cushing’s Disease
3 - Adrenal Adenoma
4 - paraneoplastic e.g. small cell lung cancer
How do you diagnose Cushing’s syndrome?
Dexamethasone suppression test
What’s the difference between primary and secondary thyroid disease?
Primary = problem is in thyroids
Secondary = problem in pituitary
Which antibody is most strongly related to Grave’s disease?
TSH receptor antibody
What biochemical picture would you see in someone with subclinical hypothyroidism?
TSH raised but T3, T4 normal
How do you manage subclinical hypothyroidism?
TSH > 10mU/L + normal free thyroxine =
consider offering levothyroxine if TSH level is > 10 mU/L on 2 occasions, 3 months apart
TSH is between 5.5 - 10mU/L + normal free thyroxine =
- if < 65 years consider offering a 6-month trial of levothyroxine AND if TSH level is 5.5 - 10mU/L on 2 separate occasions 3 months apart,and there are symptoms of hypothyroidism
What is a prolactinoma?
BENIGN tumour of pituitary gland
What symptoms of prolactinoma would you get in women? (4)
amenorrhoea
infertility
galactorrhoea
osteoporosis
What symptoms of prolactinoma would you get in men? (3)
impotence
loss of libido
galactorrhoea
How are prolactinomas treated?
DOPAMINE AGONSIT
- cabergoline
- surgery
Give 3 causes of LOW TSH
1 - thyrotoxicosis (with high T4)
2 - secondary hypothyroidism (low T4)
3 - sick euthyroid syndrome (low T4)
Give 4 causes of high TSH
1 - primary hypothyroidism (low T4)
2 - subclinical hypothyroidism (normal T4)
3 - poor compliance with thyroxine (normal T4)
What are the key features of Hashimoto’s?
goitre + hypothyroidism + anti-TPO
What is diabetes insipidus?
lack of antidiuretic hormone or a lack of response to ADH
What is nephrogenic diabetes insipidus?
Collecting ducts of the kidneys do not respond to ADH
Give 2 causes of nephrogenic diabetes insipidus
1 - lithium
2 - intrinsic kidney disease
What is cranial diabetes insipidus?
when the hypothalamus does not produce ADH for the pituitary gland to secrete
Give 4 causes of cranial diabetes insipidus
- brain tumour
- head injury
- brain infection
- idiopathic
What signs and symptoms would someone with diabetes insipidus have?
- polyuria
- polydipsia
- dehydration
- postural hypotension
- HYPERNATRAEMIA
How would you investigate someone with polydipsia?
Water deprivation test
What does a water deprivation test involve?
1 - patient should avoid taking in any fluids for 8 hours
2 - urine osmolality is measured and synthetic ADH (desmopressin) is administered
3 - 8 hours later urine osmolality is measured again.
What results would you expect in urine osmolality AFTER DEPRIVATION for a) cranial DI b) nephrogenic DI c) primary polydipsia?
cranial = low urine osmolality
nephrogenic = low urine osmolality
primary = HIGH
What results would you expect in urine osmolality AFTER ADH for a) cranial DI b) nephrogenic DI c) primary polydipsia?
cranial = high urine osmolality
nephrogenic = low urine osmolality
primary = high
What might high serum osmolality and hyponatraemia suggest?
hyperglycaemia
How would you investigate someone with low sodium?
1 - fluid status
2 - serum osmolality
3 - urine osmolality
What would high urine osmolality and hyponatraemia suggest to you?
renal loss of sodium
e.g. Addisons
renal failure
diuretics
SIADH
hypothyroidism
What would low urine osmolality and hyponatraemia suggest?
extra-renal loss (NOT KIDNEY)
- vom/diarrhoea
- burns
- CF
Which conditions cause gynaecomastia by increasing oestrogen?
- Obesity (aromatase is an enzyme found in adipose tissue that converts androgens to oestrogen)
- Testicular cancer (oestrogen secretion from a Leydig cell tumour)
- Liver cirrhosis and liver failure
- Hyperthyroidism
- Human chorionic gonadotrophin (hCG) secreting tumour, notably small cell lung cancer
+DRUGS
Which conditions cause gynaecomastia by reducing testosterone?
- Testosterone deficiency in older age
- Hypothalamus or pituitary conditions that reduce LH and FSH levels (e.g., tumours, radiotherapy or surgery)
- Klinefelter syndrome (XXY sex chromosomes)
- Orchitis (inflammation of the testicles, e.g., infection with mumps)
- Testicular damage (e.g., secondary to trauma or torsion)
+ DRUGS
If someone has galactorrhoea would you expect their prolactin to be raised or low?
RAISED
Give 4 causes of hyperprolactinaemia
1 Idiopathic (no cause can be found)
2 Prolactinomas (hormone-secreting pituitary tumours)
3 Endocrine disorders, particularly hypothyroidism and polycystic ovarian syndrome
4 Medications, particularly dopamine antagonists (i.e., antipsychotic medications)
What is the relationship between dopamine and prolactin?
Dopamine INHIBITS prolactin production
- therefore dopamine ANTAgonists i.e. antipsychotics can lead to raised prolactin’
- dopamine agonists e.g. cabergoline/bromocriptine can be used to suppress prolactin secretion
What results would you get in a low dose dexamethasone suppression test of someone with Cushing’s syndrome?
9am cortisol = normal/high
If someone has high/normal cortisol on a low dose dexamethasone suppression test - what further investigation would you arrange?
High dose dexamethasone suppression test
How would you interpret the results from a high dose dexamethasone suppression test?
High cortisol + low ACTH = adrenal adenoma
High cortisol + high ACTH = small cell lung Ca
Low cortisol = pituitary adenoma
