the pituitary gland - hyperprolactinaemia and acromegaly Flashcards
what medications can cause high prolactin?
dopamine antagonists such as anti-emetics and anti-psychotics commonly cause a high prolactin
therefore when investigating hyperprolactinaemia a full medication profile should obtained
what are some causes for hyperprolactinaemia?
- medications e.g dopamine antagonists (antipsychotics and antiemetics)
- secondary to renal failure, primary hypothyroidism, adrenal insufficiency and PCOS
- prolactinoma pituitary tumour
- pregnancy
- breast stimulation
- stress
what is a micro prolactinoma and what are some features it can present with?
commonest pituitary tumours
women>men
<1cm and present with
- menstrual disturbance
- hypergonadism in men
- galactorrhea
how is PCOS distinguished from a prolactinoma?
- androgenic symptoms
- less elevated prolactin levels
- absence of a pituitary lesions on MRI
what is a macro prolactinoma?
a type of pituitary tumour
> 1cm in size, may be very large
men>women
when levels of prolactin are extremely high, immunoassay can give inaccurately low results (the hook affect) so it may be necessary to dilute sample to achieve more accurate results
what is the treatment for prolactinomas?
- dopamine agonists, most commonly cabergoline or bromocriptine
- cabergoline is given once or twice weekly and is tolerated better than bromocriptine, which is given daily
what are the common side effects of dopamine agonists?
- nausea
- postural hypotension
- psychiatric disturbance rarely
- macro prolactinomas are treated medically and usually have good reduction. CSF leaks due to rapid reduction in size, which gives potential risk of meningitis.
- high cumulative dose of dopamine agonist is associated with cardiac valve abnormalities in Parkinson’s disease
name 2 dopamine agonists
cabergoline or bromocriptine
what is acromegaly?
caused almost exclusively by a GH secreting pituitary tumour
patients usually have for many years before diagnosis
untreated can lead to disfiguring feature and premature death from CV disease
what are the clinical features of acromegaly and features of GH hyper secretion?
- increased size of hands and feet
- facial features become coarser over time
- frontal bossing of the forehead
- protrusion of the chin
- widely spaced teeth
- soft tissue swelling causes enlargement of the tongue and soft palate, snoring and sleep apnoea
- puffiness of the hands with carpal tunnel
specific features of GH hyper secretion
- sweating
- headaches
- hypertension
- DM (may result following treatment)
what investigations are done for acromegaly?
oral glucose tolerance test (OGTT) and IGF 1 levels
Failure to suppress GH after OGTT and elevated IGF 1 levels are found in active acromegaly
how does the oral glucose tolerance test OGTT prove acromegaly?
a higher blood glucose level usually causes the body to stop producing GH.
Therefore, a doctor will purposely raise your blood glucose level using an OGTT and watch how your GH level responds. They should fall, but in acromegaly they stay the same.
Take blood before and 4 times throughout 2 hours (30, 60, 90, 120mins) to check GH and glucose levels.
If GH level doesn’t drop to below 1 ng/mL, you have acromegaly.
when imaging can be done for pituitary adenoma?
pituitary MRI
micro adenomas may need contrast enhanced scans
why may some tumours co secrete GH and prolactin?
as they share the same cell origin
therefore prolactin may be simultaneously elevated
how is acromegaly managed?
- surgery is the treatment choice. micro adenomas = high chance of remission
medically
- somatostatin analogues can help sumptoms and GH/ IGF 1 levels refractory acromegaly.
- dopamine agonists may help
- external bean or stereotactic radiotherapy may be used. Stereotactic provides more targeted treatment at higher dose, but only suitable for lesions well away from the optic chiasm.
- Radiotherapy may also take years to lower GH and can cause gradual onset hypopituitarism and possible cerebrovascular disease.
