Endo - Pituitary Tumour Flashcards
What is the outcome of a functioning somatotrophic tumour?
acromegaly
What is a functioning lactotroph tumour called?
prolactinoma
What is a functioning thyrotroph tumour called?
TSHoma
What is a functioning gonadotroph tumour called?
Gonadotrophinoma
What is a corticotroph tumour called?
Cushing’s Disease (corticotroph adenoma)
How do you classify a pituitary tumour by size?
→ microadenoma = < 1 cm
→ macroadenoma = > 1 cm
How do you classify a pituitary tumour radiologically?
→ sellar or suprasellar
→ compressing optic chiasm or not
→ invading cavernous sinus or not
How do you classify a pituitary tumour by function?
→ excess secretion of hormone
→ no excess secretion of hormone = non-functioning adenoma
How do you classify a pituitary tumour by benign or malignancy?
→ carcinoma very rare
→ mitotic index measured using Ki67 index (benign is <3%)
→ pituitary adenoma can have benign histology + malignant behaviour
What the effect of hyperprolactinaemia on the gonadotrophin hormones?
→ Prolactin binds to prolactin receptors on kisspeptin neurons in hypothalamus
→ Inhibits kisspeptin release
→ decreases downstream homrone cascade e.g. less GRH, LH + FSH, testosterone + oestrogen
What is the most common functioning pituitary adenoma?
prolactinoma
What is the size of the prolactinoma usually proportional to?
serum prolactin
How does the prolactinoma present?
→ Menstrual disturbance → Erectile dysfunction → Reduced libido → Galactorrhoea → Subfertility → Oligo-amenorrhoea → Osteoporosis
What are the alternative physiological cause of elevated prolactin?
→ pregnancy / breastfeeding
→ stress (exercise, seizure, venepuncture)
→ nipple/chest wall stimulation
What are the alternative pathological causes of elevated prolactin?
→ primary hypothyroidism
→ polycystic ovarian syndrome
→ chronic renal failure
What are the alternative iatrogenic (drug-related) causes of elevated prolactin?
→ antipsychotics → SSRIs → anti-emetics → high dose oestrogen → opiates
How do you confirm true elevation of serum prolactin?
→ no diurnal variation
→ not affected by food
→ consistent with clinical features
What are the 2 possible explanations if a mild prolactin elevation has no consistency with clinical features + the medical history has been reviewed?
→ macroprolactin
→ stress
What is macroprolactin?
→ “sticky prolactin”
→ a polymeric form of prolactin
an antigen–antibody complex of monomeric prolactin + IgG (normally <5% of circulating prolactin)
→ Recorded on assay as elevation of prolactin – needs alternative method to confirm (macroprolactin screening test)
Why can stress cause a false positive elevation in serum prolactin?
→ stress of venepuncture (unsure why)
→ measure 20 minutes apart with indwelling cannula to minimise venepuncture stress
What’s the next step after a true elevation of prolactin has been confirmed?
pituitary MRI
How is prolactinoma treated?
→ first-line = medical
→ dopamine receptor agonists
e.g. CABERGOLINE
(bromocriptine doesn’t work as well) (also safe in preganancy)
→ aim to normalise serum prolactin + shrink prolactinoma
How do dopamine receptor agonists work?
→ dopamine receptor agonists mimic the dopamine released from hypothalamic dopaminergic neurones
→ inhibits release of prolactin from lactotrophs
What is the result of excess GH in children? Why?
gigantism
→ growth plates still active
What is the result of excess GH in adults? Why?
acromegaly
→ growth plates are closed
What are the symptoms of acromegaly?
→ Sweatiness → Headache → Coarsening of facial features → Macroglossia (huge tongue) → Prominent nose → Large jaw - prognathism → Increased hand and feet size → Snoring & obstructive sleep apnoea → Hypertension → Impaired glucose tolerance/diabetes mellitus
How is acromegaly diagnosed? What test is done to confirm acromegaly?
→ measure GH after oral glucose load
→ serum GH levels should decrease in normal person
→ serum GH has paradoxical increase in acromegalic (prolactin often increases too)
→ should also have elevated serum IGF-1
What is done after excess GH is confirmed?
pituitary MRI
Why is it important to treat acromegaly?
→ increased risk of DM
→ increased cardiovascular risk
How is acromegaly treated?
→ first-line = surgical
→ trans-sphenoidal pituitary surgery
→ aim to normalise serum GH + IGF-1
→ Can use medical treatment prior to surgery to shrink tumour or if surgical resection incomplete e.g. Somatostatin analogues eg octreotide – ‘endocrine cyanide’ or Dopamine agonists eg cabergoline (GH secreting pituitary tumours frequently express D2 receptors
What is Cushing’s syndrome vs. Cushing’s disease?
→ both = too much cortisol or other glucocorticoid
→ Cushing’s disease is due to specifically a pituitary adenoma
What are causes of Cushing’s?
ACTH dependent → adrenal adenoma or carcinoma → taking steroids by mouth ACTH independent → pituitary dependent Cushing's disease → ectopic ACTH (lung cancer)
What are the symptoms of Cushing’s?
→ mental changes → red cheeks → fat pads → striae → easy bruising → moon face → centripetal obesity → hypertension, etc...
What clinical investigation results indicate Cushing’s Disease?
→ elevation of 24hr urine free cortisol (due to excess cortisol)
→ elevation of late night cortisol (loss of diurnal rhythm)
→ failure to suppress cortisol after oral dexamethasone (oral glucocorticoid) (should be supressed due to negative feedback)
What’s next after determining elevated cortisol levels?
measure ACTH to determine whether cause is ACTH dependent/independent
What are non-functioning pituitary adenomas?
→ don’t secrete any specific hormone
→ often present with visual disturbance (bitemporal hemianopia)
→ can present w hypopituitarism
→ serum prolactin could be raised if dopamine can travel down from hypothalamus
How are non-functioning pituitary adenomas treated?
trans-sphenoidal surgery is needed for larger tumours, especially for the visual disturbance
