Pituitary Tumors Flashcards
What do pituitary tumors of somatotrophs cause?
Acromeglay
What do pituitary tumors of lactotrophs cause?
Prolactinoma
What do pituitary tumors of thyrotrophs cause?
TSHoma
What do pituitary tumors of gonadotrophs cause?
Gonadotrophinoma
What do pituitary tumors of corticotrophs cause?
Cushings disease (corticotrophadenoma)
How are pituitary tumors classified radiologically?
Size, micro or macrodenoma (less or more than 1cm), sellar or suprasellar, invading optic chiasm or not, invading cavernous sinus or not
How are pituitary tumors classified functionally?
Is there excess secretion of a specific pituitary hormone or not (non functioning adenoma)?
How are pituitary tumors classified as benign or malignant?
Mitotic index measured, benign if <3%
NOTE: can have benign histology but display malignant behaviour
Where is the cavernous sinus found?
The sides of the pituitary gland
What is special about pituitary tumors that invade the cavernous sinus?
They are non operable- many important structures are present in cavernous sinus eg cranial nerves and carotid artery
Are most pituitary tumors functioning or not?
Non functioning and benign- not carcinomas
Are most pituitary tumors benign or malignant?
Benign
Describe the hormonal axis in hyperprolactinaemia
Excess prolactin
Binds to kisspeptin neurons in hypothalamus
Less kisspeptin released
Reduced release of GnRH from hypothalamus
Reduced release of LH/FSH from anterior pituitary
Reduced oestrogen (women) and testosterone (men)
How is GnRH released in the body?
Pulsatile in puberty
What are the physiological effects of hyperprolactinaemia?
Oligo-amenorrhea, low libido, infertility, osteoporosis
Why does hyperprolactinaemia cause osteoporosis long term?
Bones require sex hormones (oestrogen and testosterone) for strength
What is the most common pituitary adenoma?
Prolactinoma
How does size of prolactinoma effect prolactin levels?
Serum prolactin is proportional to tumor size, bigger tumor=more prolactin
How do prolactinomas present?
Menstrual disturbance, erectile dysfunction, reduced libido, galactorrhea (milk production from breast), subfertility (no sperm production or egg release)
What are causes of elevated prolactin other than prolactinomas?
Physiological= pregnancy/breastfeeding, stress (venepuncture, exercise, seizure), nipple stimulation Pathological= primary hypothyroidism, PCOS, chronic renal failure Latrogenic= antipsychotics, SSRIs, high dose oestrogen, opiates
How do we confirm elevated serum prolactin isnt a false positive?
If there is mild elevation, check that they have at least one symptom thats expected if not, consider:
Macroprolactin= instead of circulating as singular molecules, the prolactin sticks together in big clumps
Stress of venepuncture= exclude this by a cannulated prolactin series
How are prolactinomas treated?
Medical not surgical
Use a dopamine receptor agonist eg cabergoline to normalise serum prolactin and shrink tumors
How do dopamine receptor agonists work?
Dopamine binds to D2 receptors on lactotrophs which prevents prolactin release, the agonist does the same
What happens to growth plates when you grow up?
They fuse so you stop growing
What are presentations of acromeglay?
Sweatiness Headache Macroglossia Prominent nose Large jaw Snoring/sleep apnoea Larger hand and feet
Describe the mechanisms of GH
Body tissues metabolic actions leads to growth and development
Increases IGF-1
How is acromegaly diagnosed?
Check if IGF-1 is high
Give them a 75g drink of glucose, in acromegaly GH will go up for normal people it should go down
What is the main risk for those with acromegaly?
Increased cardiovascular risk
What happens when someone has excess cortisol?
Cushings syndrome
What are the causes of Cushings?
ACTH dependant or independant: Too many oral steroid Adenoma of corticotrophs Cancer of lung= too much ACTH Tumor of adrenal gland
How do we investigate Cushings?
Observe urine cortisol for 24 hrs (will be constantly high in Cushings) Elevation of late night cortisol (via blood test) Give dexomethasone (cortisol will still be high in Cushings)
How do non functioning pituitary tumors commonly present?
Visual disturbance eg bitemporal hemianopia
What can non functioning tumors surprisingly present with?
Hypopituitarism- stops all hormones being secreted
What happens to prolactin in non functioning tumors and why?
Cant be raised as dopamine cant travel down pituitary stalk from hypothalamus
How are non functioning tumors treated and when?
Trans sphenoidal surgery but only if close to optic chiasm to prevent visual disturbance
What medicine is given for acromegaly?
Octreotide- GH agonist
