Pituitary Tumours Flashcards
What do somatotrophs produce?
Growth Hormone / somatotrophin
What do lactotrophs produce?
Prolactin
What do thyrotrophs produce?
Thyroid stimulating hormone (TSH/thyrotrophin)
What do gonadotrophs produce?
Luteinising hormone (LH) Follicile stimulating hormone (FSH)
What do corticotrophs produce?
Adrenocorticotrophic hormone
ACTH/corticotrophin
What does a tumour affecting somatotrophs result in?
Acromegaly (adults)
Gigantism (children)
What does a tumour affecting lactotrophs result in?
Prolactinoma
What does a tumour affecting thyrotrophs result in?
TSHoma
What does a tumour affecting gonadotrophs result in?
Gonadotrophinoma
What does a tumour affecting corticotrophs result in?
Cushing’s disease (corticotrophasdenoma)
How is a pituitary tumour classified from an MRI?
- Size:
<1cm : microadenoma
>1cm : macroadenoma - Location
- Suprasellar or sellar
- Whether it is compressing the optic chiasm or not
- Whether it is invading the cavernous sinus or not
How is a pituitary tumour classed based on it’s function?
- excess secretion of a pituitary hormone
- no excess secretion, therefore a: non-functioning adenoma
How is a pituitary tumour classed as either benign or malignant?
(carcinomas are very rare, <0.5%)
Using the mitotic index (Ki67 index), with benign being <3%
It is possible for pituitary adenomas to have a benign histology but display malignant behaviour
How does hyperprolactinaemia (caused by a prolactinoma) inhibit kisspeptin neurons?
- prolactin binds to prolactin receptors on kisspeptin neurons in the hypothalamus
- inhibits kisspeptin release
- decreases in downstream (GnRH/LH/FSH/T/Oest)
- leading to oligo-amenorrhoea/low libido/infertility/osteoporosis
Describe prolactinomas?
- Most common functioning pituitary tumour
- serum prolactin >5000mU/L
(proportional to the size of the tumour)
How to prolactinomas present?
- menstrual disturbance
- erectile dysfunction
- reduced libido
- galactorrhoea
- subfertility
What are other possible causes of elevated prolactin levels?
Physiological - pregnency/breastfeeding - stress: exercise, seizure, venepuncture - nipple/chest wall stimulation Pathological - primary hypothyroidism - PCOS - chronic renal failure Iatrogenic - antipsychotics - SSRIs - Anti-emetics - High dose oestrogen - Opiates
What is macroprolactin?
a polymeric form of prolactin
- an antigen-antibody complex of monomeric prolactin and IgG (normally <5% of circulating prolactin)
- limited bioavailability and bioactivity
Why is it necessary to confirm a ‘true’ elevation in serum prolactin?
Macroprolactin and stress of a venepuncture can present as an elevation of prolactin (which is false), therefore an alternative method is needed to confirm
How to reduce the effect of the stress of venepuncture on prolactin measurements?
Exclude using a cannulated prolactin series
- sequential serum prolactin measurements 20 minutes apart with an indwelling canulla to minimise stress.
How to diagnose a prolactinoma?
- confirm an elevated level of serum prolactin
- a pituitary MRI
How to treat a prolactinoma?
Medical (first line)
- dopamine receptor agonists
- cabergoline (bromocriptine)
- safe during pregnancy
- dosage depends on size of the prolactinoma (micro = smaller dose)
- Aim: normalise serum prolactin and shrink the prolactinoma.
How do dopamine receptor agonists work?
They bind to D2 receptors to inhibit the release of prolactin
How does acromegaly present?
Sweatiness Headache Coarsening of facial features - Macroglossia - Prominent nose - Prognathism Increased hand and feet size Snoring and obstructive sleep apnoea Hypertension Impaired glucose tolerance/diabetes mellitus
How to diagnose acromegaly?
- elevated serum IGF-1
- Failed suppression (‘paradoxical rise’) of GH following oral glucose load
(oral glucose tolerance test) - Raised prolactin (due to co-secretion)
Once GH excess confirmed, Pituitary MRI.
How to treat acromegaly?
Surgery (First Line) - trans-sphenoidal pituitary surgery Aim: normalise serum GH and IGF-1 Medication (Second Line) (shrink pre-surgery or if surgical resection is incomplete) - somatostatin analogues eg: octreotide 'endocrine cyanide' - dopamine agonists eg: cabergoline (GH pituitary tumours often express D2 receptors) Radiotherapy (slow)
What causes Cushing’s syndrome?
excess cortisol or other glucocorticoid ACTH-dependent: - Cushing's disease (corticotrophadenoma) - Ectopic ACTH (lung cancer) Independent - oral steroids (common) - adrenal adenoma or carcinoma
What is Cushing’s disease?
Excess ACTH due to a corticotrophadenoma
How to diagnose Cushing’s Disease?
- elevation of 24hr urine free cortisol - increased secretion
- elevation of late night cortisol (salivary or blood test) - loss of diurnal rhythm
- failure to supress cortisol after oral dexamethasone
(exogenous glucocorticoid) - increased cortisol secretion
Once confirmed hypercortisolism, measure ACTH.
If high, pituitary MRI
How do non-functioning pituitary adenomas present?
- no specific hormone secretion
- often cause visual disturbance
(bitemporal hemianopia) - occasional hypopituitarism
- elevated serum prolactin (dopamine can’t travel down the pituitary stalk)
How to treat visual disturbance caused by non-functioning adenomas?
Trans-sphenoidal surgery
also can be used if the tumour is large
