Flashcards in Endocrine - Online MedEd - Anterior pituitary Deck (35):
Posterior pituitary is a continuation of which structure
-Hypothalamus has neurons that go into the posterior pituitary
ACTH causes secretion of...
for BP control
Hypo --> CRH --> Ant pit --> ACTH --> target organ --> adrenal --> hormone is cortisol (respond to stress/increase blood glucose)
Hypo --> TRH --> TSH --> thyroid --> release T4 --> metabolic activity
Hypo --> GHrH --> GH --> liver --> insulin-like growth factor 1 --> causes growth
GnRH --> FSH/LH --> reproductive organs --> testosterone and estrogen --> reproduction
What is the negative feedback loop?
Original hormones from pituitary and hypothalamus get produced (default)
Distal hormone turns off proximal hormones
Prolactinoma - what is it?
Prolactin secreting tumour
Not a cancer
Presentation - prolactinoma
Women - amenorrhea, galactorrhea - present with microadenomas (unlike men were tumours present bigger, this is because women will notice these symptoms). As the tumours are small there is no visual field deficit
Men - don't have breasts that produce milk, can't notice amenorrhea and galactorrhea - symptoms are reduced libido, will get macro adenoma, may get bitemporal hemianopsia
Where does the pituitary sit and what can it affect?
Diagnosis of prolactinoma
Check meds that might increase prolactin - like DA antagonists
TSH - hypothyroidism can induce prolactinoma
Check PRL level
Need MRI to look for tumour*
Treatment of prolactinoma
Use dopamine agonists - cabergoline better than bromocriptine
Rarely will need surgery and radiation
Prolactin and dopamine - what relationship?
Dopamine inhibits prolactin
So dopamine antagonists (such as antipsychotics) disinhibit inhibition on prolactin --> cause prolactinoma like symptoms, reason for noncompliance
Prolactin and TRH relationship?
TRH stimulates prolactin
So in hypothyroid --> low T4, elevated TRH --> prolactinoma
Prolactinoma - what labs/imaging
Measure TSH - if hypothyroid, will be high and treat with levothyroxine
If normal TSH, get prolactin level --> if elevated PRL, get MRI
MRI positive - prolactinoma --> use dopamine agonists
Acromegaly - what is it?
Growth hormone secreting
Can cause cancer cells to grow, other cells
Acromegaly - presentation
Kids look different than adults
-Kids before closure of growth plates, cause long bones to grow - gigantism
-Adults after fusion of growth plates, all things that can grow, will! Hands, feet, face, visceral organs, will also get Diabetes (because GH causes glucose to rise)
-Hands don't fit, hat resized
What is the killer in acromegaly in adults?
Diastolic heart failure - LV hypertrophy is so bad!
Acromegaly - diagnosis?
Check insulin-like growth factor 1
If elevated, do glucose suppression test
If glucose suppression test is positive, then get an MRI
Only treatment for acromegaly
Can use octreotide/somatostatin (turns insulin like growth hormone to stasis)
What does growth hormone tell the liver?
Make glucose - diabetes
Make insulin-like growth factor 1 - stimulate bones, and heart to grow
What is the glucose suppression test?
If suppression test suppresses glucose, then not acromegaly
-Give someone an oral glucose load, what should happen is insulin should increase to lower glucose; other hormones should shut off
-Positive test, is when GH that should decrease, does not change!
Regulation of insulin?
Epinephrine, growth hormone, cortisol
Insulin tries to bring down glucose
Hypopituitarism - presentation
1) Sudden, acute, devastating - causes: infection, infarction, iatrogenic (i.e. take too many tumour during surgery) - catastrophic
2) Chronic, insidious - causes: autoimmune, deposition disease, slow growing tumour that gradually presses on stalk
Loss of cortisol by adrenal removal can lead to catastrophic symptoms
Loss of T4 presents with
Diagnosis of hypo pit?
Assess levels of cortisol and T4 - random level
Treatment of hypo pit?
Replace with hormones
Infarct of pituitary
Get coma right after
Large tumour recognized
Obtunded, nuchal rigidity, headache
Patient will try to preserve in chronic hypo pit. What is the main hormones?
3) GH less important - fatigue
4) FSH/LH - loss of libido/menstruation
*Very vague symptoms
How to diagnose hypo pit that is chronic?
Because ACTH and TSH will be preserved
Test the GH by using an insulin stimulation test, can also do the vasopressin stimulation test
If these are positive, check MRI
Insulin stimulation test - how does it work?
If give insulin, BG will fall
Epi, GH, and cortisol will be stimulated
Failure for GH to rise means a lack of these hormones
Treatment of hypo pit that is chronic?
Replace hormones and fix the underlying disease and treat underlying disease