🧪Endocrinology🧪 - Pituitary tumours Flashcards
What is the name of the condition caused by a functioning somatotroph tumour?
Acromegaly/gigantism(in children)
What is the name of a functioning lactotroph tumour?
Prolactinoma
What is the name of a functioning thyrotroph tumour?
TSHoma
What is the name of a functioning gonadotroph tumour?
Gonadotrophinoma
What is the name of a functioning corticotroph tumour?
Cushing’s disease (corticotroph adenoma)
What are the 3 categories by which pituitary tumours can be classified?
Radiologically (MRI)
Function
Benign or malignant
How can pituitary tumours be classified radiologically?
Size:
-microadenoma <1cm/10mm
-macroadenoma >1cm/10mm
Sellar or supresellar
Compressing optic chiasm or not
Invading cavernous sinus or not
How can pituitary tumours be classified by function?
Excess secretion of a specific pituitary hormone, named after that hormone (e.g. prolactinoma)
OR
No excess secretion of pituitary hormone (non functioning adenoma)
How can pituitary tumours be classified as benign or malignant?
Pituitary carcinoma is very rare (<0.5%)
Pituitary tumours can have benign histology but display malignant behaviour - space is so confined than any growth will be invasive/aggresive
What kind of pituitary tumour is shown here, and how would the patient be presenting?
Tumour shown is suprasellar (expanded beyond the sella turcica) and is compressing the optic chiasm significantly
Macroadenoma
Patient extremely likely to be reporting visual defects (e.g. bitemporal hemianopia)
What would be the effect of a prolactinoma?
Greatly increased prolactin levels
Prolactin inhibits kisspeptin release, so also shut down of the GPH axis
What are some key facts about prolactinomas?
Commonest functioning pituitary adenoma
Usually serum [prolactin] >5000 mU/L - significantly higher than normal, diagnosis will be very clear
Serum [prolactin] proportional to tumour size
How will a patient with a prolactinoma present?
Menstrual disturbance (women)
Erectile dysfunction (men)
Reduced libido
Galactorrhoea (women)
Subfertility
Why is galactorrhoea occurring in men very rare in cases of prolactinomas?
Galactorrhoea (lactation) very very rare in men, need oestrogen to prime/develop breasts to lactate
What conditions will be caused by a prolactinoma?
Secondary hypogonadism - hypogonadotrophic hypogonadism
What are the physiological causes of an elevated prolactin?
Pregnancy/breastfeeding
Stress: exercise, seizure, venepuncture
Nipple/chest wall stimulation
What are the other pathological causes of an elevated prolactin, other than a prolactinoma?
Primary hypothyroidism (features low T3/T4 and high TSH, high TSH stimulates prolactin production - unknown mechanism)
Polycystic ovarian syndrome (also not fully understood, thought to be related to hormonal imbalance and hypothalamus dysfunction)
Chronic renal failure
What are the iatrogenic causes of an elevated prolactin?
Antipsychotics
Selective serotonin re-uptake inhibitors
Anti-emetics
High dose oestrogen
Opiates
What is the first step once a true pathological elevation in prolactin has been identified?
A pituitary MRI
What is shown in this image?
Sellar microadenoma
What is shown in this image?
Suprasellar macroadenoma - not yet reached, but is approaching, the optic chiasm
What is the treatment for a prolactinoma?
First-line treatment is medical not surgical
Dopamine receptor agonists - cabergoline (bromocriptine)
Safe in pregnancy
Aim is to normalise serum prolactin & shrink prolactinoma
Microprolactinomas will need smaller doses than macroprolactinomas
How do dopamine receptor agonists work?
Lactotrophs (including those in prolactinomas) have D2 receptors on their surfaces
Dopamine binds to these, which inhibits prolactin secretion
Dopamine receptor agonists also bind to these receptors, and so also stop prolactin secretion
What conditions would a pituitary tumour secreting excess GH lead to?
Acromegaly(adults)/Gigantism(children)
How does acromegaly present?
Often insidious presentation – mean time to diagnosis from onset of symptoms = 10y
Sweatiness
Headache
Coarsening of facial features: Macroglossia, prominent nose
Lage jaw - prognathism
Snoring/obstructive sleep apnoea
Hypertension
Impaired glucose tolerance/DM
What is the mechanism of growth hormone action?
Acts directly on body tissues, stimulating growth
AND/OR
Acts on the liver, stimulating IGF-1 (and IGF-2) to be released, which acts directly on body tissues, stimulating growth
How is acromegaly diagnosed?
GH pulsatile - random measurement unhelpful
Elevated serum IGF-1
Failed suppression of GH following oral glucose load
Why dose acromegaly need to be treated in a timely manner?
Increased CVD risk in untreated acromegaly
What is the first line treatment for acromegaly?
Surgery - trans-sphenoidal pituitary surgery
Aim to normalise serum GH and IGF-1
What can be used in conjunction with surgery to treat acromegaly?
Can use medical treatment prior to surgery to shrink tumour or if surgical resection incomplete
Somatostatin analogues e.g. octreotide – ‘endocrine cyanide’
Dopamine agonists e.g. cabergoline (GH secreting pituitary tumours frequently express D2 receptors)
What is the difference between Cushing’s syndrome and Cushing’s disease?
Cushing’s syndrome = excess cortisol due to any underlying cause
Cushing’s disease = specifically a pituitary corticotroph adenoma secreting ACTH
What investigations can be used to confirm Cushing’s disease?
Elevation of 24h urine free cortisol - increased cortisol in blood
Elevation of late night cortisol - salivary/blood test - loss of diurnal rhythm
Failure to suppress cortisol after oral dexamethasone
What are the steps in confirming that a case of Cushing’s syndrome is actually Cushing’s disease?
Once confirmed hypercortisolism, measure ACTH
If ACTH high (ACTH dependent), pituitary MRI
What are the ACTH dependent and independent causes of hypercortisolism?
ACTH dependent
-Cushing’s disease (pituitary corticotroph adenoma)
-Ectopic ACTH (eg lung cancer)
ACTH independent
-Taking steroids by mouth (common)
-Adrenal adenoma or carcinoma
How does a non-functioning pituitary adenoma present?
Don’t secrete any specific hormone
Often present with visual disturbance (bitemporal hemianopia)
Can present with hypopituitarism
Serum prolactin can be raised (dopamine can’t travel down pituitary stalk from hypothalamus, so no inhibition of prolactin) - won’t be raised in most cases, but is possible
Any prolactin raise will be mild
