Endo 2: Hypersecretion of anterior pituitary hormones Flashcards
Define hyperpituitarism
- symptoms associated with excess production of adenohypophysial hormones
What is hyperpituitrism usually due to?
- usually due to isolated pituitary tumors
- but also can be ectopic
What kind of hyperpituitarism often associated with ?
- often associated with visual field
- and endocrine related symptoms
Describe what is bitemporal (heteronymous) hemianopia
BASICALLY: loss of peripheral vision with optic chiasm compression
- at optic chasm –> fibers from nasal part of both retina cross
- light from left visual field –> hits right part of retina
(and vice versa) - due to crossing over, all light from left visual field = detected by right side of brain
- pituitary tumor can protrude out of sella turcica –> and disrupt the fibres coming from nasal parts of the retina
- meaning you can lose temporal part of the visual field
- -> can see in nasal field
- -> can’t see in temporal fields
Excess release of ACTH =
cushing’s disease
Excess release of TSH =
thyrotoxicosis
Excess release of LH + FSH =
precocious puberty in children
Excess release of Prolactin =
hyperprolactinaemia
Excess release of GH =
gigantism, acromegaly
What is hyperprolactinaemia ?
What is it associated with?
- excess circulating prolactin
- not due to physiological cause such as pregnancy / breast-feeding
associated with:
- pituitary tumors (prolactinoma)
What are effects of hyperprolactinaemia (due to pituitary adenoma) in women?
women:
effects:
- galactorrhea
- secondary amenorrhoea
- loss of libido
- infertility
What are effects of hyperprolactinaemia (due to pituitary adenoma) in men?
men:
- galactorrhea = uncommon
- loss of libido
- erectile dysfunction
- infertility
What is the effect of high levels of prolactin on the reproductive axis?
- decreases LH + FSH levels
- leads to secondary amenorrhoea
- loss of libido
- infertility
Give methods of treatment of hyperprolactinaemia
dopamine receptor (D2) agonists:
- decreases prolactin secretion
- reduces tumor size
e.g bromocriptine, cabergoline
What are some side effects of dopamine receptor agonists
- nausea + vomiting
- postural hypotension
- dyskinesias
- depression
- pathological gambling
Describe patterns of acromegaly
- describe its onset
- has an insidious onset
- signs/symptoms progress gradually
What happens if acromegaly = untreated?
- untreated excess GH
- leads to increased morbidity + mortality
- increased CVD/ Resp complication/ cancer
What grows in acromegaly?
- periosteal bone
- cartilage
- fibrous tissue
- connective tissue
List clinical features of acromegaly
- excessive sweating
- headache
- enlargement of supraorbital ridges/noes/hands/feet
- macroglassia
- mandible grows –> prognathism
- carpal tunnel syndrome
- barrel chest
describe the metabolic effects of acromegaly
and how it takes place.
- excess growth hormone
- insidious onset
- causes increase in endogenous glucose production +
decreased muscle glucose uptake - which causes increase in insulin production
- insulin resistance occurs
- leads to DIABETES MELLITUS
What are complications associated with acromegaly?
- obstructive sleep apnoea
- hypertension
- cardiomyopathy
- increased risk of cancer
explain the relationship between acromegaly + prolactin
- in acromegaly
- prolactin level = high
- reflects tumor secreting GH + prolactin
- hyperprolactinaemia
what are 3 methods for diagnosis acromegaly?
- GH pulsatile
- elevated serum IGF-1
- Oral glucose tolerance test (Failed suppression of GH following oral glucose load )
Describe graph of glucose induced suppression of GH secretion in acromegaly
-
Give methods of treating acromegaly
- surgery (1st line)
- somatostatin analogues
(e. g octreotide) - dopamine agonists
(e. g cabergoline) - radiotherapy
What is the effect of somatostatin analogues ?
- Reduces GH secretion + tumor size
How is somatostatin analogue administered?
- injection
What are possible GI side effects of somatostatin analogues?
- nausea
- diarrhea
- gallstones
how is high levels of prolactin linked with secondary gonadism?
high levels of prolactin –> causes suppression of GnRH pulsatility
- which can cause secondary hypogonadism
regulation of prolactin
- prolactin = always inhibited
- less inhibition –> prolactin release
- less dopamine binding to D2 receptor
- -> more prolactin secretion
- you can mimic dopamine
how can you mimic dopamine?
- D2 receptor agonists
act similarly to dopamine
How would you diagnose acromegaly?
- elevated serum IGF 1
- gold standard = oral glucose tolerance test
- ->
What test is used to diagnose acromegaly and how are the results interpreted?
- Oral glucose suppression test
