Session 8: Pituitary Disorders Flashcards
Common clinical presentations of pituitary tumours.
Mass effect of tumour leading to headache and visual loss.
The visual loss depends on how the pituitary tumour grows.
Superior growth leads to visual field loss in form of bitemporal hemi-anopia by pressure on optic chiasm.
If there is lateral growth of the tumour it can lead to pain and double vision.
If it invades the cavernous sinus cranial nerve palsy may ensue like Horner’s syndrome and ptosis.
What happens to the hormones of the pituitary in the case of hypopituitarism?
GH, LH/FSH, TSH and ACTH goes down since they are under positive control.
Prolactin goes up because it is under negative control.
What is the usual order of loss of hormones due to pituitary tumour?
GH -> LH -> FSH -> TSH -> ACTH -> PRL
Following the order of how hormone secretion is usually affected in a growing pituitary tumour how will the different stages manifest itself?
GH deficiency leading to reduced quality of life in adults and short stature in children.
Gonadotropin deficiency leading to loss of secondary sexual characteristics in adults and loss of periods. Erectily dysfunction and trouble conceiving.
TSH and ACTH deficiency is life-threatening and can lead to Addison’s disease and hypopituitarism.
TSH deficiency leads to low thyroid hormones, cold, weight gain, tiredness, slow pulse and low T4 and non-elevated TSH.
ACTH deficiency leads to low cortisol, tiredness, dizziness, low BP, low sodium.
What are the most common pituitary tumours causing excess of hormone secretion?
Which are rare?
Prolactin, GH and ACTH.
TSH and LH/FSH are rare.
Remember that this is tumours causing excess and not deficiency.
How do you test the thyroid axis?
functional T4 and TSH
How do you test the gonadal axis?
LH and FSH
Testosterone or oestradiol
How do you test prolactin axis?
Serum prolactin
How do you test HPA axis?
09.00 cortisol
How do you test growth hormone axis?
GH and IGF-1
What are dynamic assessments of HPA and GH axes?
Stimulation tests and suppression tests.
When would you do a stimulation test or a suppression test?
Stimulation test when you suspect hormone deficiency
Suppression test when you suspect hormone excess
Give examples of tests of the adrenal axis suspecting deficiency of ACTH.
Direct stimulation of adrenals by ACTH like synACTHen
Response to hypoglycaemic stress because insulin stress test.
Give examples of test suspecting excess of adrenal axis.
Suppression of ACTH axis with steroids like dexamethasone.
This is to see if ACTH goes down in response to the increased dexamethasone. If the ACTH goes down you can expect a pituitary adenoma. If ACTH stays high you can expect an ectopic tumour like small cell lung cancer.
Give examples of tests suspecting either deficiency or excess of GH axis.
Deficiency do a hypoglycaemic stress test (insulin stress test)
Excess suppress the GH axis with glucose load to check the glucose tolerance. (Glucose tolerance test)
In addition to serum and dynamic tests how can you assess a suspect pituitary disorder?
By MRI
How are macro-prolactinomas best treated?
With dopamine agonist because it will start shrinking. Kind of use it or lose it.
If the prolactin levels are unusually low even for a prolactinoma but still elevated (<5000) what might you expect?
A tumour pressing on the stalk making dopamine unable to inhibit the secretion of prolactin. This means that the tumour doesn’t secrete prolactin itself but rather inhibits dopamine from making its way to the lactotropes.
So if prolactin is >5000 suspect a prolactinoma
If <5000 suspect a tumour blocking dopamine from inhibiting prolactin secretion.
Why is this important?
Because prolactinomas can usually be treated surgically but non-functioning pituitary tumours cannot. They must be treated surgically.
How might hormone levels present in a non-functioning pituitary adenoma?
All other hormones (LH/FSH, ACTH, TSH and GH) might be low but prolactin might be high.
Give example of dopamine antagonists and their side-effects.
Anti-sickness and anti-psychotic drugs.
They can cause high prolactin levels (hyperprolactinaemia)
This means that it is important to check medication before sending patient away. Also check for pregnancy.
Long-term complications of untreated acromegaly.
Premature cardivascular death
Inreased risk of colonic tumours
Probably increased risk of thyroid cancer
Disfigured body which may be irreversible
Hypertension and diabetes
Unpleasant symptoms in general
Tests to confirm acromegaly.
OGTT with GH response
Failure to suppress GH
Elevated IGF-1 levels
Treatment of acromegaly
Surgical removal
Additional treatment such as dopamine agonists to reduce GH secretion like Cabergoline and bromocriptine.
Somatostatin analogues
Pegvisomant which is a GH receptor blocker.
Radiotherapy
What is diabetes insipidus?
There are two types: Cranial DI and Nephrogenic DI.
Cranial DI is becasuse of vasopressin (ADH) deficiency in pituitary disease.
Nephrogenic DI is due to vasopressin (ADH) resistance in kidney disease.
Types of pathology that cause cranial DI.
Inflammation
Infiltration
Malignancy
Infection
Why is it uncommon for a tumour to cause cranial DI?
Because standard pituitary tumours just affect anterior pituitary not posterior.
Consequences of untreated DI.
Severe dehydration
Hypernatraemia
Reduced consciousness, coma and death.
How do you treat cranial DI?
Synthetic vasopressin like desmopressin which is either nasal spray, tablets or injection.
Clinical presentation of pituitary apoplexy (stroke either by haemorrhage or infarction)
Sudden onset headache
Double vision
Visual field loss
Cranial nerve palsy
Hypopituitarism
