6 normal pituitary function and disease Flashcards
what happens to prolactin levels if pituitary stalk is damaged and why?
increase in prolactin levels- loss of communication with hypothalamus and anterior pituitary
prolactin’s principle control is inhibitory
TRH has stimultatory role
what is the most common cause of pituitary disease?
pituitary tumour
10% of all intracranial neoplasm
Mostly benign, slow-growing (years) adenomas
define adenoma
macroadenoma
microadenoma
benign tumours of epithelial tissue of glangular origin
>10mm diameter
<10mm diameter
how can adenomas cause problems?
- Over-production of a pituitary hormone
- Inadequate production of other hormones- pituitary gland cells push against edges of bony compartment
- Local effects on anatomically-related structures (visual disturbances, headaches- increase in intracranial pressure)
prevelance of tumours
what proportion are endocrine active tumours?
what is the main type (40-50%)?
3/4 are endocrine active tumours
Prolactinoma (40-45%) hyperprolactinaemia
GH-secreting (20%) acromegaly (adults), gigantism (children)
ACTH-secreting (10-15%) Cushing’s disease
LH/ FSH-secreting: rare
TSH-secreting: rare
Non-functioning (20-25%) mechanical symptoms- headaches, facial disturbances (non-secreting) hypopituitarism – low levels of hormones: most likely consisting of chromophobes
investigations of pituitary tumour
- signs and symptoms
- endocrine investigation: baseline hormone levels
dynamic tests:
stimulation- if hyposecretion suspected
suppression- if hypersecretion suspected
- imaging: CT or MRI
example of stimulation test:
secondary hypothyroidism
Inject more TRH (hypothalamus), normally stimulate TSH (ant pituitary). Failure to stimulate TSH/ T4 suggests deficiency of TSH. (lack of response to exogenous TRH)
example of suppression test:
acromegaly (GH tumour)
Oral glucose tolerance test – high plasma [glucose] normally suppress GH release. Failure to lower GH secretion suggests GH tumour.
management of pituitary disease due to tumour:
- Pharmacological management
- Surgery- preferred method
- Radiotherapy
what are two types of surgery for pituitary tumour?
which is more common?
- Craniotomy - through the skull above the eye.
- Trans-sphenoidal - through the nose. Most common. Less invasive, patients in hospital less time, better recovery time
hyperprolactinaemia:
- most common causes
- symptoms
- treatment
- Most common cause is prolactinoma. (adenoma secreting pro lactin)
- Another is damage to the pituitary stalk (dopamine)
- Symptoms: loss of fertility/ libido, galactorrhoea- milky discharge from breast tissue
- high [prolactin] inhibit GnRH release
- Gynaecomastia m>f benign glandular tissue of breast tissue
- Treatment: mainly with dopamine receptor agonists (e.g. cabergoline, bromocriptine) which inhibit prolactin secretion and shrink tumour.
- Surgery / radiotherapy considered with tumours resistant to drug therapy.
acromegaly
- what is it?
- what is the term that happens in childhood?
- common cause
- treatment
- symptoms
- who could detect early acromegaly?
- Excessive growth hormone secretion in adulthood
(Excessive GH secretion in childhood leads to extremely tall stature (gigantism))
- Most common cause is GH-secreting tumour
- Treatment: principally surgical removal of tumour, radiotherapy in some patients.
- Somatostatin analogues (e.g. octreotide, lanreotide) inhibit GH release.
- Bromocriptine (dopamine receptor agonist). Some GH-adenomas have expression of dopamine receptors, which when activated inhibit GH release.
- coarsening of facial features (look older than their age)
- enlarged hands and feet
- headaches, vision disturbance
- sleep apnoea, general tiredness
- hypertension, cardiomegaly
- glucose intolerance (diabetes)
- irregular or loss of periods (females); impotence (males)
- As lower jaw enlarges, gaps appear between teeth
Acromegaly may be detected early by dentists
hypopituirarism
define pan- hypopituitarism
- what is it usually caused by
treatment
deficiency of one or more pituitary hormones
Pan-hypopituitarism = deficiency of all pituitary hormones
- Usually caused by pituitary adenoma, surgery/ radiotherapy of the pituitary.
- Severe head trauma can damage pituitary stalk.
treatment: hormone replacement
what are potential side effects of surgery and radiotherapy of a pituitary tumour?
hypopituitarism and damage to optic pathways
what is Cushing’s syndrome?
what can cause it?
what is the main cause?
treatment
excess glucocorticoid activity
caused endogenously and exdogenous (steroid meds)
main cause: endogenous- ACTH secreting anterior pituitary tumour
treatment: remove tumour (radiotherapy too)
