Pituitary tumours Flashcards
What terminology is used to describe the size of a pituitary tumour?
Microadenoma <1cm (10mm)
Macroadenoma >1cm (10mm)
Sellar: stay in the sella turcica
suprasellar: situated or rising above the sella turcica (outgrowth)
2 types:
* Compressing optic chiasm or not
* Invading cavernous sinus or not
What is a functioning/ non-functioning tumour?
- Excess secretion of a specific pituitary hormone
eg prolactinoma (Functioning adenoma) - No excess secretion of pituitary hormone (Non Functioning Adenoma)
Are pituitary tumours usually benign or malignant? why?
- Usually benign (pituitary carcinomas are v. rare)
- Pituitary adenomas can have benign histology but display malignant behaviour
- Do not metastasize, but not a lot of room for maneuver; complications caused even without spreading
What is a prolactinomas?
Pituitary tumour that leads to hyperprolactinaemia
* Commonest functioning pituitary adenoma
* Usually serum [prolactin] >5000 mU/L
* Serum [prolactin] proportional to tumour
size
What causes the presentations of prolactinomas
- Prolactin binds to prolactin receptors on kisspeptin neurons in hypothalamus
- Inhibits kisspeptin release.
- Decreases in downstream GnRH/LH/FSH/T/Oest
(known as “secondary hypogonadism”) - Causes symptoms: Oligo-amenorrhoea/Low
libido/Infertility/Osteoporosis
What are some symptoms of prolactinomas?
- Menstrual disturbance
- Erectile dysfunction
- Reduced libido
- Galactorrhoea (milky nipple discharge unrelated to the normal milk production of breast-feeding)
- Subfertility
- Milk production outside of post partum lactation- even seen in men sometimes
What are some physiological causes of elevated prolactin levels?
- Pregnancy/breastfeeding
- Stress: exercise, seizure, venepuncture (blood test)
- Nipple/chest wall stimulation
at this point, patient requires medical advice- no need to see a specialist
What are some pathlogical causes of elevated prolactin levels?
- Primary hypothyroidism (thyroid gland not working, T4 decrease, TSH increaes, TRH increases- TRH can also stimulate prolactin production
- Polycystic ovarian syndrome
- Chronic renal failure (kidney usually removes prolactin- not excerted; builds up)
What are the treatment steps after confirmed pathological elevation of serum prolactin?
- Organise a pituitary MRI (if prolactinoma confirmed provide further treatment)
How do you treat a prolactinomas?
- First-line treatment is medical not surgical
- Dopamine receptor agonists mainstay of
treatment (dopamine inhibits prolactin release) - 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 reduce prolactin and shrink prolactinomas?
- Anterior pituitary lactotrophs have D2 receptors on them
- Dopamine from hypothalamic dopaminergic neurones bind to D2 receptors
- Act as an off switch to the prolactin production
- D2 receptor agonists mimic the dopamine & tumour shrinks
What 2 conditions are caused from a pituitary tumour secreting excess GH?
- Gigantism (children)
- Acromegaly (adults)
What are the presentations of acromegaly?
- Often insidious presentation (proceeding in a gradual, subtle way, but with very harmful effects)– mean time to diagnosis from onset of symptoms = 10y
- Sweatiness
- Headache
- Coarsening of facial features
- Macroglossia (tongue is larger than normal.)
- Prominent nose
- Large jaw - prognathism
- Increased hand and feet size
- Snoring & obstructive sleep
apnoea - Hypertension
- Impaired glucose
tolerance/diabetes mellitus
Describe the mechanisms of growth hormone action?
- Growth hormone releasing hormone released from hypothalamus
- Growth hormone released from the anterior pituitary
-acts DIRECTLY on the body tissues= growth and development
-INDIRECTLY: - GH acts on liver- IGF-1 released from liver and that acts on the body tissue= growth and development
How do you diagnose acromegaly?
- GH pulsatile – so random measurement unhelpful
- Elevated serum IGF-1
- Failed suppression (‘paradoxical rise’) of GH following oral glucose load – oral glucose tolerance test
- Prolactin can be raised – cosecretion of GH & prolactin
- Once confirm GH excess, pituitary MRI to visualise
pituitary tumour
