Pituitary Tumours Flashcards
What are the 5 types of functioning pituitary tumours that can occur?
Somatotrophs can cause acromegaly. Lactotrophs can cause prolactinomas. Thyrotrophs cause TSHoma (very rare). Gonadotrophs cause gonadotrophinoma. Corticotrophs cause Cushing’s disease/corticotroph adenoma.
What are the 3 ways pituitary tumours can be classified?
Based on radiological features, function or whether it is beningn/malignant.
What are radiological features of pituitary tumours?
- Size. If below 1cm - microadenoma. If above - macroadenoma.
- Sellar/suprasellar
- Compressing optic chiasm or not
- Invading cavernous sinus or not - if it is, may not be possible to treat patient as difficult to surgically access this area without damaging internal carotid artery/cranial nerves which run through this space.
What are functional features of tumours?
- Excess secretion of a specific pituitary hormone
3. If no excess secretion - known as Non-Functioning Adenoma
What are benign vs malignant classifications ?
Carcinomas only make up <0.5% of pit tumours. Ki67 index used to measure mitotic index - if this is less than 3%, is benigh.
Pituitary adenomas can have benign histology but display malignant behaviour.
What problems does hyperprolactinaemia cause?
Prolactin binds to prolactin receptors on kisspeptin neurons in hypothalamus. Inhibits kisspeptin release and therefore, GnRH not stimulted. Downstream LH/FSH/Oestrogen decreased leading to oligomenorrhoea/amenorrhoea, low libido, infertility, osteoporosis.
What are 4 key points about prolactinomas?
- Commonest functioning pituitary adenoma
- Serum prolactin >5000mU/L
- Serum prolatin is proportion to tumour size.
- Normal prolactin is around 300mU/L in men and 600mU/L in women.
What is the presentation of prolactinomas?
Menstrual disturbance, Erectile dysfunction, Reduced libido, Galactorrhoea, Subfertility.
GERMS
What are physiological causes of elevated prolactin?
- Pregnancy/breastfeeding
- Stress: Exercise, Seizures or Venepuncture
- Nipple/Chest Wall Stimulation
What are 3 pathological causes of elevated prolactin?
Primary hypothyroidism, Polycystic ovarian syndrome, Chronic renal failure (kidneys don’t excrete prolactin properly)
What are 5 iatrogenic causes of high prolactin?
- Anti-psychotics
- SSRIs
- Anti-emetics
- High dose of oestrogen
- Opiates
SAAHO
What 2 things could be indicated by a mild elevation of prolactin with no other clinical symptoms?
- Macroprolactin
2. Stress of venepuncture
What is macroprolactin?
Monomeric prolactin is biologically active and majority of circulating is monomeric. However, macroprolactin is a circulating form of prolactin which is polymeric and is an antigen-antibody complex of monomeric prolactin and IgG. This is usually less than 5%. Assay records this as elevated but has limited bioavailability and bioactivity. Not dangerous.
How can stress of venepuncture be eliminated?
Cannulated protein series can be done taking sequential measurements every 20 minutes with indwelling cannula.
How is prolactinoma treated?
If true pathological elevation is confirmed, pituitary MRI done. Dopamine receptor agonists used first (cabergoline/bromocriptine) which is safe in pregnancy. Aim is to normalise serum prolactin and shrink the prolactinoma. Dose determined based on whether it is a micro/macroprolactinoma.
How do dopamine receptor agonists work?
Lactotrophs have D2 receptors which dopamine binds to, inhibiting prolactin release. D2 receptor agonists are selective synthetic analogues of dopamine and bind to the same receptor, reducing prolactin output.
What occurs if pituitary tumour secretes excess GH?
Gigantism occurs in children while acromegaly occurs in adults.
How is acromegaly diagnosed?
Insidious onset of symptoms so mean time to diagnosis is 10 years. Sweatiness, headache, macroglossia, prominent nose, prognathism, hand and feet size increased, snoring + obstructive sleep apnoea, hypertension, impaired glucose tolerance/diabetes mellitus.
How does growth hormone act?
Somatotrophin acts on body tissues and stimulates liver to produce IGF-1 and IGF-2 (Somatomedin) which have similar action. Causes growth and development.
How is acromegaly diagnosed?
GH release is pulsatile so one-time direct measurement unhelpful. Look for:
- Elevated serum IGF-1
- Failed suppression of GH following oral glucose load - should decrease GH in normal individual but leads to a paradoxical rise in acromegalic individual. Prolactin can be raised also and pituitary MRI needed.
How is acromegaly treated?
First surgical: trans-sphenoidal pituitary surgery. Aim is to normalise serum GH and IGF-1. Prior to surgery, medical treatment used to shrink tumour or if surgical resection incomplete:
1. Somatostatin analogues e.g. octreotide
2. Dopamine receptor agonists e.g. cabergoline (D2 receptors expressed by GH secreting tumours)
Radiotherapy can also be used.
If untreated, increased cardiovascular risk.
What are the symptoms of Cushing’s?
Thin skin Proximal myopathy Centripetal obesity (lemon on sticks) Diabetes, hypertension and osteoporosis Immunosuppression (reactivation of TB) Moon face Striae Mental changes (depression) Red cheeks
MIRTS DCP
What are the causes of Cushing’s DISEASE?
Taking steroids by mouth (common)
Pituitary dependent Cushing’s disease (pituitary adenoma)
Ectopic ACTH (lung cancer)
adrenal adenoma or carcinoma
Occurs due to excess cortisol/glucocorticoid
How can the causes of Cushing’s SYNDROME be classified?
ACTH dependent:
- Corticotroph adenoma
- Ectopic ACTH in lungs
ACTH independent:
- Taking steroids by mouth
- Adrenal adenoma/carcinoma
