ENDO- Pituitary Flashcards
What is origin of the anterior pituitary
comes from the upper palate, back of throat
What is development of the posterior pituitary
neuron in origin
Why is the location of the pituitary is an issue
close to the optic chiasm and can cause issue when enlarged;
near cavernous area (vessels, etc) so it can make it inoperable
How is the anatomy of the posterior pituitary
direct connection from the brain to the posterior pituitary via neurons
What is the anatomy of the anterior pituitary
anterior can still function if the stalk is cut because it is signaled through blood vessels
What is the thyroid axis
Hypothalamus -> TRH -> Pituitary -> TSH -> Thyroid -> T4
What is the adrenal axis
Hypothalamus -> CRH -> Pituitary -> ACTH -> Adrenal Gland -> Cortisol
What is the release pattern of cortisol
circadian rhythm, usually peaked in the morning
Wha is the growth hormone axis
1] Excititory: Hypothalamus -> GHRH -> Pituitary -> GH -> Liver cell -> IGF;
2] Inhibitory: Hypothalamus -> somatostatin -> Pituitary -> inhibits GH release
Describe the Male & Female Gonadotropin axis
Hypothalamus -> GnRH -> Pituitary -> LH, FSH -> Testes/Ovaries ->
Organs- Inhibin (negatively feedbacks on pituitary) and
testosterone/estrogen (negatively feedbacks on hypothalamus)
Describe the female Gonadotropin axis just before ovulation
Hypothalamus -> GnRH -> Pituitary -> LH, FSH -> ovaries -> Inhibin (negatively feedbacks on pituitary) and
estrogen (POSITIVELY feedbacks on hypothalamus)
Describe the prolactin axis
Hypothalamus -> dopamine and neural stimuli inhibits -> Pituitary -> Prolactin -> mammary gland
What are the hallmarks of pituitary dysfunction
1] Wrong hormone at the wrong time,
2] Inappropriate hormone release given the expected milieu
3] Lack of expected hormone
what happens when Low blood volume or high osmolarity of the blood?
hypothalamus- posterior pituitary - ADH to act on the kidneys. RETAIN NA, thus water
What happens if posterior pituitary tract is destroyed
unable to release ADH in response
What is elevated cortisol from any source?
Cushing Dz., rare
Central/Pituitary from elevated pituitary ACTH
S/S
1] thin skin/purple striae,
2] supraclavicular fat pads,
3] proximal muscle weakness
What diagnostic tools are used for Cushing’s Syndrome
1] Screen 24 hr urine free cortisol and/ or
2] late night salivary cortisol
What is next step if elevated cortisol of 24 hr urine free cortisol test?
1] use low dose dex, to suppression pituitary
2] check ACTH at the same time
What if ACTH low and low dose dex suppression is inadequate/ doesn’t dec cortisol?
then= adrenal Cushing’s,
LOW ACTH mean pit not release like it should
if ACTH normal or high, then pituitary or ectopic
How would you differentiate between pituitary or ectopic Cushing’s syndrome?
use HIGH dose dex suppression to differentiate pituitary vs. ectopic;
suppression = cushing’s syndrome;
no suppression=is ectopic
How do you get a late night salivary cortisol sample
Saliva sample at 11 pm to 12 midnight
Cortisol circadian
How is the dexamethasone suppression test
increases cortisol levels to see if negative feedback to ACTH
Dex is a steroid, that less invasive on body
What is the next step in management of Cushing’s Disease?
1] Image what is necessary, pituitary vs. adrenal
2] Consider vein sampling to lateralize mass
What are the treatments of Cushing’s?
1] surgery,
2] radiation, preferable gamma knife,
3] medications that decrease the synthesis of cortisol
Describe the special consideration for large masses
evaluation for loss of other pituitary functions is appropriate
Describe gigantism
excess GH is before closure of epiphyses, long bone growth
Describe acromegly
excess GH is after closure of epiphyses; circumferential bone growth (widened, rather than longer)
What lab value is used to confirm gigantism or acromegly
IGF-1 796 (nl 90-450 ng/mL), because growth hormones comes out in pulses
What are the treatments for gigantism or Acromegaly
1] generally surgery,
2] radiation, preferable gamma knife,
3] medications decrease GH release or block its binding to the receptor
Describe the characteristics of Acromegaly
1] Rare, 2] Insidious Onset, 3] coarse features. 4] Enlarged tongue, 5] Deep voice, 6] Large joints in hands, 7] old pictures to make a diagnosis
What are the cause of hyperprolactinemia
1] MC is pregnancy which is normal, 2] prolactinoma
What inhibits the production of prolactin?
Dopamine Agonist therapy for hyperprolactinemia
List the Dopamine Agonists
1] bromocriptine (long-term safety in pregnancy),
2] cabergoline (longer acting)
What should follow dopamine Agonist therapy
MRI to check for shrinkage of mass
What are possible causes of non-hormone function tumors?
1] pure non-functioning,
2] meningioma,
3] cancer
Describe the treatment of Panhypopituitarism
1] first remove or shrink the mass,
2] All the hormones need to be replaced: Steroids first for the adrenal insufficiency,
3] After 2 days, thyroid and testosterone therapy
Describe the characteristics of diabetes insipidus
Lots of low osmolarity urine and hypernateremia
ADH not responding
What tests should be done to confirm diabetes insipidus
1] Water deprivation
2] Vasopressin (ADH will cause retention challenge 5mcg SQ x one
Describe the Vasopressin challenge
DI is central(HP ant)-if urine osm increases by >50% then the kidneys are responding (ADH will make osmol HIGH)
DI is nephrogenic; if urine osm does not change, then the kidneys are NOT responding vasopressin ADH
Describe the incidence of diabetes insipidus
1] Rare, Can be seen isolated.
2] rarely associated with anterior pituitary function loss
why water deprivation is necessary in diabetes inspidus patients?
People who complain of polyuria/polydipsia usually have normal sodiums.
They just drink a lot of water to keep up.
What are exteremely rare endocrine masses?
1] gonadotrope (FSH/LH) secreting masses,
2] TSH secreting masses leading to incr free T4, 3isolated pituitary TSH loss without loss of other axes
how to determine what pituitary disorder is going on
1] Determine if low or high levels,
2] Is it endorgan or pituitary,
3] If theres a mass is it making something?,
4] Is mass blocking the release of something else?
Should A normal TSH with a low free T4 be of concern?
very suspicious for pituitary disease and rarely occurs alone. Work it up.
