Hypersecretion of anterior pituitary hormones Flashcards
what causes hyperpituitarism?
- autoimmune stimulation of TSH (Graves)
- isolated pit tumours (can also be ectopic)
- drugs like amiadrone
what defects are usually associated with hyperpituitarism due to a tumour?
visual field defects e.g. bitemporal hemianopia (Optic chiasm proximity)
both eyes may be affected
effect of excess ACTH
Cushing’s Disease
effect of excess TSH
thyrotoxicosis
effect of excess LH/FSH in children
precocious puberty in children
effect of excess prolactin
hyperprolactinaemia
effect of excess GH
gigantism, acromegaly
what are the physiological causes of hyperprolactaemia?
pregnancy, breastfeeding
describe the pathological causes of hyperprolactinaemia
prolactinoma ( micro adenoma <10mm)
- most common functioning pit. tumour making the hormone
- high prolactin suppresses GnRH pulsatility
what is the effect of high prolactin on GnRH?
suppresses GnRH pulsatility
what are the signs in women for hyperprolactinaemia?
galactorrhoea
secondary ammenorrhoea/oligomennorhoea
loss of libido
infertility
what are the signs in men for hyperprolactinaemia?
galactorrhea (uncommon)
erectile dysfunction
loss of libido
infertility
how can you switch off prolactin production?
dopamine from dopaminergic neurones bind to D2 receptors on lactotrophs to switch off prolactin secretion
what is the treatment for hyperpituitarism?
- remove tumour causing it e.g.
D2 receptor agonists (stimulate D2 receptors) - surgery (trans- sphenoidal)
- radiation
first line of treatment given orally before surgery
what is the effect of D2 receptor agonists?
decrease prolactin secretion and reduce tumour size
what are the side effects of using D2 receptor agonists?
- nausea
- postural hypotension
- dyskinesia (loss of voluntary movement)
- depression (exhausted dopamine stores)
- pathological gambling, hypersexuality
examples of D2 receptor agonists
bromocriptine
cabergoline
what distinguishes gigantism and acromegaly
children get gigantism
adults get acromegaly
they are usually due to a benign GH secreting pit. adenoma
describe the onset and death due to acromegaly
gradual but harmful onset
when left untreated, excess GH is associated with increased morbidity and mortality
death: CVS (60%), resp complications (25%) and cancer (15%)
what features grow in acromegaly?
- periosteal bone
- cartilage
- fibrous tissue
- connective tissue
- internal organs like the liver
what are the clinical features of acromegaly?
- hyperhidrosis
- polydipsia
- headache
- tiredness
- supraorbital ridge enlargement
- big nose, hands, feet
- thickened lips
- frontal bossing
- macroglossia
- prognathism (protrusion of lower jaw)
- carpal tunnel syndrome (leads to tingling fingers)
- barrel chest
- kyphosis
diagnosis of acromegaly
photographs of the patient from before physical changes occurred
how does acromegaly leads to the development of diabetes mellitus?
excess GH inhibits insulin
increased insulin resistance
impaired glucose tolerance
reduced uptake by muscles
DM
what are the complications of acromegaly ?
- obstructive sleep apnoea due to soft tissue growth in the throat
- hypertension: GH mediated Na+ reabsorption
- cardiomyopathy: hypertension, DM, toxic effects of GH on myocardium
- cancer: colonic polyps
alongside GH what else to acromegaly patients produce a lot of?
prolactin
this mean a tumour is secreting both Gh and prolactin
the hyperprolactinaemia will cause a secondary hypogonadism
how is acromegaly diagnosed?
- GH is pulsatile
- GH should drop in a healthy person as insulin rises with a glucose load
- in acromegaly, there is a paradoxical rise in GH
- an elevated serum IGF-1 can be measured
how is acromegaly treated (first line)?
first line- surgery with trans-sphenoidal entry to remove tumour
medication involved in acromegaly treatment?
somatostatin analogues or dopamine agonists
how are somatostatin analogues used to treat acromegaly?
Injected or administered in a monthly depot injection.
GI side effects common, e.g. nausea, diarrhoea, gallstones.
Reduces GH secretion and tumour size.
Also used as a pre-treatment before surgery (shrinks’ tumour).
Can be used post-operatively if not cured or whilst waiting for radiotherapy to take effect.
example of somatostatin analogue
octreotide
example of dopamine agonist
cabergoline
why may glucose be found in the urine of acromegaly patients?
excess GH suppressed insulin so high glucose will remain high so needs to be expelled in the urine
