Pituitary Tumours Flashcards
What is acromegaly?
Abnormal excess GH production in adults
What are the causes of acromegaly?
Benign GH secreting pituitary adenoma
Ectopic GHRH carcinoid tumour
Describe the epidemiology of acromegaly
Rare - 3mil annually
M=F
Describe the normal function of GH
GH binds to G-coupled protein receptors on liver to stimulate the release of IGF-1
IGF-1 causes soft tissue and bone growth
What is the pattern of secretion of GH?
Pulsatile secretions, greater secretions at night
By ant pit gland
What stimulates the release of GH?
GHRH - growth hormone releasing hormone from the hypothalamus
What inhibits the secretion of GH?
Somatostatin - more potent
also glucose and dopamine
Why may patients w acromegaly present with vision loss and headaches?
Pit tumour may compress/ put pressure on surrounding structures
- optic chiasm -> bitemporal hemianopia
What are the signs and symptoms for acromegaly?
Signs-
Enlarge hands, feet, jaw,
Wide nose, big tongue
Carpal tunnel syndrome
Puffy lips, widely spaced teeth
Symptoms-
Vision loss, headaches, acroparaesthia (pins and needles)
Incr. sweating, sleep apnea, stiff joints
What are the investigations and results for acromegaly?
Serum IGF-1 = raised
Oral glucose tolerance test
- 75g glucose and GH measured- remain high
MRI- pit adenoma
Vision test
Why is random serum GH unreliable for diagnosing acromegaly?
As it has a pulsatile release
What is the treatment for acromegaly
- trans-sphenoidal suregry to remove tumour
- drugs to reduce GH production
somatostatin analogue IM lanreotide
dopamine agonist
GH receptor antagonist
During which part of the day has the highest GH secretion?
Night
What is the normal physiological effects of GH?
Proteinsynthesis
Gluconeogenesis and inhibits insulin
Lipolysis
How does GH mediate its effects?
Binds to liver to secrete IGF-1 (insulin gowth factor)
What is a prolactinoma?
prolactin secreting pituitary adenoma
What is hyperprolactinaemia?
abnormally high prolactin levels usually due to a prolactinoma
How may dopamine contribute to causing hyperprolactinaemia
Tumors which suppress the release of dopamine will increase the secretion of prolactin
As dopamine has an inhibitory effect on prolactin
What is the normal physiological effect of prolactin?
Regulates breast development
Stimulates breast milk production
What is the clinical presentation of prolactinomas?
Headache/ bitemporal hemianopia
Amenorrhoea, infertility
Galactorrhoea
Decr. libido/ erectile dysfunction
What are the investigations and results for prolactinomas?
3x high serum prolactin
TFT
Pit gland MRI
What is the relationship between TSH and prolactin
TSH stimulates the secretion of prolactin
What is the treatment for prolactinomas?
Dopamine agonist eg bromocriptine or cabergoline
