Pituitary function Flashcards
posterior pituitary
ADH
oxytocin
measuring hormones
know whether you are expecting deficiency or excess
measure at the appropriate time of day
for deficiency measure at the peak (eg cortisol in the morning)
for excess, measure at the lowest point (eg midnight for cortisol)
often dynamic blood tests are required. try to stimulate hormones in deficiency, and suppress in the case of excess, using the bodies own negative feedback loops. eg dexamethasone test
pituitary disease
can rarely be congenital, but far more often acquired, most often by a space occupying lesion
ectopics
rare
result in hormone excess
optic chiasm
classic appearance of bitemporal temporal hemianopia in the presence of a pituitary mass
pituitary adenomas
can produce one or more hormones or none at all
can result in a picture of excess and deficiency
typical order of hormone loss in pituitary mass:
GH>LH>FSH>TSH>ACTH>prolactin
people usually become symptomatic around LH/FSH
opthalmoplegia
nerves contolling eye muscles compressed and eye muscles paralysed
pituitary compression caused by rupture
typical hormone loss
ACTH>TSH>GH>FSH>LH
vital to replace corticosteroids immediately to avoid death
primary
problem with the organ secreting the relevant hormone eg adrenals
secondary
problem higher up in the axis, eg the pituitary
pigmentation
increased ACTH increased melanocyte stimulating hormone, leading to pigmentation of the skin
this is only seen in primary conditions, as the pituitary produces higher levels of ACTH to try and stimulate hormone secretion at the target organ
addisonian crisis
hypovolaemic shock D&V hypoglycaemic abdo pain lower back pain afebrile
medical emergency - easily treatable, but fatal if missed immediate priorities: aggressive fluid resus - 1L saline stat parenteral glucocorticoid correct hypoglycaemia
hyperaldosteronism
stubborn high BP
hypokalaemia
low magnesium
metabolic alkalosis
conn’s syndrom
aldosterone producing adrenal adenoma (primary)
thyroid deficiency
treated with levothyroxine
thyrotoxicosis
Grave’s disease
prolactin
suppressed by dopamine rather than hormonal regulation
therefore dopamine antagonists, such as antipsychotics, will result in a hyperprolactinemia
any mass in the pituitary stalk that blocks dopamine delivery from the hypothalamus to the pituitary will have the same effect
dopamine agonists to treat hyperprolactinemia
acromegaly
high levels of growth hormone
stable, florid clinical features
increased interdental spacing sweating high BP impaired glucose tolerance leading to DM carpal tunnel coarse facial features
tested by glucose tolerance test and failure of GH to respond to high blood glucose
diabetes insipidus
essentially a failure of ADH (vasopressin)
central: failure of production in the pituitary
nephrogenic: failure of action on the kidney
polyuria
thirst
tend towards dehyydration
hypernatraemia (only when unable to drink sufficient to compensate the large fluid loss)
treated with desmopressin (an ADH analogue), which is essential in patients with diabetes insipidus. omission can lead to death
multiple endocrine neoplasia
MEN1, MEN2
