Lecture 83 - Pituitary Disorders Flashcards
why is random plasma hormone testing not helpful?
what other tests should you consider if you suspect a deficiency in a hormone ?
If you suspect an excess of a hormone what should you consider?
hormones are cycling throughout the day (cortisol is lowest at midnight, peaks at 8am);
When suspecting hormone deficiencies, consider stimulation testing
For suspected hormone excess, consider suppression testing
inputs to the HPA axis that stimulates cortisol
what is the HPA axis?
Pain, pleasure, fear, anxiety, inflammation, hypoglycemia, depression
Hypothalamus –> CRH –> Pit —>ACTH –> Adnrenal —> Cortisol
Cortisol has negative feedback on levels of CRH and ACTH
what tests are are used to stimulate cortisol
cosyntropin (ACTH analog) test –
insulin tolerance test (ITT) – induces hypoglycemia which stimulates CRH
what the difference between primary and secondary adrenal insufficiency?
how can you differentiate between the two based on labs?
what is the best test for secondary hypothyroidism ?
Primary – due to direct adrenal failure (will have low cortisol, but high ACTH)
secondary – problem at the Pit or Hypothalamus (will have low CRH/ACTH + low cortisol)
secondary: ITT
Suspected Results for ITT and Cosyntropin tests for primary vs secondary adrenal insufficiencies?
Cosyntropin –
Primary – abnormal
Secondary - normal
ITT –
Primary – abnormal
secondary - abnormal
Cushing’s syndrome
whats the ddx for the etiology?
whats the most common exogenous etiology vs endogenous etiology
cortisol excess
Pitutiary adenoma (most common from endogenous)
Exogenous steroids (most common exogenous + overall cause) (such as those given for inflammatory)
Adrenal Tumor
Ectopic – Lung cancer (Small cell), carcinoid tumor
three bests diagnostic tests for hypercortisolism?
24 hour urine free cortisol (most specific)
Overnight 1 mg dexamethasone suppression test – should be low the next morning; but if Cushing’s state, then the cortisol will still be high
Midnight salivary free cortisol
tests for localization of the tumor
ACTH
if Adrenal – too much cortisol = negative feedback = low ACTH
If central/ectopic = normal or high ACTH
MRI - of brain
effects of too much cortisol
Cushing's features obesity moon facies poor bone and muscle strength Buffalo hump etc
what is Psueo-cushing state?
what can cause it?
Mild hypercortisolism in patients who have features of cushing’s
Hypercortisolism often seen in patients with clinical features
and
Generalized obesity
Active alcohol abuse
Depression
what is the thyroid axis
TRH –> TSH –> T3, T4
what is the most common cause of hypothyroid?
what is the level of TSH and T3/4?
in what other setting is the axis depressed?
how do you differentiate between primary and secondary hypothyroid based on labs ?
Hashimoto’s Disease
High TSH (b/c no neg feedback) Low T3, T4
Commonly depressed in very ll patients (neuro-endocrine response to severe illness)
Central (secondary) = low TRH, low T3, T4
Thyroid (primary) = low T3, T4 but high TRH
central vs primary hyperthyroidism:
how to you use labs to differentiate
whats the most common cause of primary hyperthyroid?
Central = High TSH, High T3, T4
Primary hyperthyroid (graves) = Low TSH, High t4, T3
Most common Primary = Graves Disease
what is Laron dwarfism? what are the GH labs?
what can these patients be treated with?
Normal GH levels
form of dwarfism in which the receptor is defective (therefore “effective” GH)
IGF1 (insulin like growth factor) is a possible treatment
beneficial effects of GH therapies for adults with GH deficeincy
Decreases in total and visceral body fat
Increase in muscle mass and bone density
Improved CV performance
Can help prevent HTN, Dyslipidemia, Insulin resistance, vascular effects, inflammation, osteoporesis
