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endocrine - pituitary
n/a
58
Accounting
Pre-School
03/02/2010

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Term
which cells are found in the central mucoid wedge? lateral wings?
Definition
wedge: corticotrophs, thyrotrophs; lateral wings: lactotrophs, somatotrophs. (gonadotrophs scattered in all 3 areas)
Term
what does vasoactive intestinal polypeptide stimulate the release of (from pituitary)?
Definition
ACTH, FSH/LH, GH, TSH/PRL, PRL
Term
what are the 2 inhibitory hormones that act on the pituitary?
Definition
somatostatin (inhibits GH); dopamine (inhibits PRL)
Term
what is the etiology of pituitary adenomas
Definition
constant stimulation of pituitary gland by trophic hormones of hypothalamus --> cell susceptible for mutations, increased mitogenic response facilitating proliferation of transformed clones into formation of an adenoma (and estrogen is a tumor promoter)
Term
what are the genes responsible for initiating tumorogensis?
Definition
GNAS and its mutant form gsp (mutation and loss of regulation); MEN-1 (mutation and loss of suppression)
Term
what are the genes responsible for promoting tumorogenesis?
Definition
P53, ras, rb, nm-23, cmyc, PTTG, p16
Term
why is estrogen a tumor promoter
Definition
it induces transcription of target genes that govern cell proliferation
Term
acidophils secrete which hormones
Definition
GH and PRL
Term
basophils secrete which hormones
Definition
GH, PRL, ACTH, LH/FSH
Term
what prolactin level is diagnostic of prolactinoma?
Definition
>200 ng/mL
Term
how do we treat prolactinomas?
Definition
bromocriptine therapy (dopamine agonist) shrinks cells. surgery is ultimate rx
Term
what are acidophil stem cell adenomas?
Definition
secrete PRL and GH, NOT responsive to bromocriptine rx, more aggressive than regular prolactinomas (common in MEN-1 and carney's complex)
Term
overgrowth findings in GH adenomas are initiated by what?
Definition
insulin-like growth factor 1 (hepatic overprod stimulated by excess GH)
Term
how to tx GH adeomas?
Definition
somatostatin analogues (shrinkage rare), usually surgery is primary tx
Term
truncal obesity, moon facies, buffalo hump, abdominal striae, osteoporosis...?
Definition
cushings disease
Term
how do we tx cushings disease?
Definition
radiosurgery, drugs, radiotherapy
Term
what is the most common type of pituitary adenoma to present with pituitary apoplexy?
Definition
gonadotropin producing adenoma
Term
how do gonadotropin producing adenomas present?
Definition
usually with mass effect (visual disturbances, headache); less so with endocrine sx (amenorrhea in women, loss of libido in men) - large and invasive tumors
Term
how do we tx gonadotropin producing adenomas?
Definition
transphenoidal surgery with adjuvant radiation rx(medical tx not effective)
Term
presentation of non-functioning/null cell adenoma?
Definition
mass effect (large and invasive) tx with surgery + radiation
Term
describe carney complex
Definition
autosomal dominant, caused by mutations in PRKAR1A gene encoding protein kinase A. characterized by CARDIAC (myxoma), ENDOCRINE (GH or prolactin PA), CUTANEOUS (naevi) and NEURAL TUMORS (psammomatous melanotic schwannomas)
Term
what is required to dx pituitary carcinoma?
Definition
CSF or systemic metastasis
Term
metastatic tumors of pituitary most commonly come from which organ? what is the usual clinical presentation?
Definition
breast (then lung), diabetes insipidus and chiasmal compression
Term
what is sheehan's syndrome?
Definition
panhypopituitarism d/t ischemic necrosis of pituitary gland during post-partum period (hypotension following postpartum hemorrhage makes previously enlarged gland of pregnant woman vulnerable to ischemia)
Term
what is pituitary apoplexy?
Definition
extensive, acute hemorrhage (or hemorrhagic necrosis) of pituitary gland or adenoma --> acute onset or worsening of sx (ha, visual impairment, cranial nerve palsies, increased ICP, meningeal signs, coma, sudden death!)
Term
describe what causes lymphocytic hypophysitis and whos affected by it?
Definition
inflam disorder of ant pituitary (autoimmune etiology). assoc with other autoimmune diseases, females during preg or post-partum. enlargement of inflamed pituitary can clinically and radiologically mimic PA --> progressive hypopituitarism
Term
what is the tx of lymphocytic hypophysitis?
Definition
steroids, immunosuppressive rx and surgery
Term
how do we distinguish between rathke's cleft cyst and PA?
Definition
rathke's is lined by ciliated columnar epithelium and mucous producing goblet cells
Term
what is central diabetes insipidus?
Definition
vasopressin/ADH deficiency d/t hypothalamic-posterior pituitary pathologies (polyuria, polydipsia, inappropriately dilute urine)
Term
what two hormones stimulate prolactin secretion?
Definition
ESTROGEN and TRH (seratonin in men, therefore antidepressants man elevate prolactin secretion)
Term
what effects do estrogen have on lactation?
Definition
estrogen stimulates prolactin secretion and also increases the number and size of lactotropes and they also block prolactin effects at the level of the breast and prevent lactation during pregnancy (lactation occurs when estradiol levels fall after birth)
Term
high levels of prolactin inhibit what?
Definition
pituitary release of gonadotropins and the peripheral effect of gonadotropins on the gonads
Term
what secretes inhibin and what is the action of this hormone?
Definition
produced in testes and ovary, inhibits FSH secretion
Term
why do we not see salt craving and hyperkalemia in secondary adrenal insufficiency? why do we not see hyperpigmentation?
Definition
aldosterone secretion is normal because it is primarily regulated by angiotensin, not ACTH; and ACTH levels are not elevated therefore no hyperpig
Term
what is the gold standard test for diagnosing central adrenal insufficiency?
Definition
Insulin Tolerance Test (give insulin and measure cortisol at 0, 30, and 60 min; cortisol >18 mcg/dL = normally functioning hypothalamic-pituitary-adrenal axis. test is adequate if a glucose of <40 mg/dL is achieved) idea: we induce hypoglycemia by giving insulin --> hypoglycemia is a strong stimulus to release ACTH by hypothalamus
Term
what morning cortisol level is consistent with dx of adrenal insufficiency?
Definition
<3 mcg/dL (early morning); >18 mcg/dL is evidence of adequate cortisol secretion
Term
what is ACTH stimulation test used for?
Definition
for dx of CHRONIC adrenal insufficiency. give ACTH via IV and measure cortisol at 0, 30, 60 min. cortisol >18 mcg/dL = normal adrenal func. not helpful for acute central adrenal insuff (may take wks-mos after ACTH reduction for adrenal glands to atrophy)
Term
what do we have to keep in mind in interpreting serum cortisol levels in women with estrogen therapy or pregnancy?
Definition
high estrogen --> increase in cortisol binding globulin --> increase in total cortisol levels (normal cortisol level may not indicate adequate cortisol secretion)
Term
how does hyperprolactinema cause amenorrhea?
Definition
increased prolactin --> increased dopamine --> alters endogenous GnRH levels and therefore affects spontaneous LH release.
Term
what effects does hyperprolactinemia have on men?
Definition
presentation: large tumors, headache, visual sx; causes hypogonadism, decreased libido, impotence, infertility d/t oligospermia
Term
how do we approach a patient with hyperprolactinemia?
Definition
r/o preg, meds that increase PRL, hypothyroidism, and renal failure. then do MRI scan
Term
how do we tx people with prolactinomas (macro and micro)
Definition
micro: leave alone and follow; or use bromocriptine if fertility is desired; macro: bromocriptine and surgery if its not shrinking
Term
indications for surgery on macroprolactinomas
Definition
inability to tolerate dopamine agonist therapy, unresponsiveness to therapy, increasing tumor size despite medical therapy
Term
how do we diagnose acromegaly?
Definition
oral glucose challenge test --> (should suppress GH) GH level cannot be suppressed below 1 ng/mL
Term
when measuring IGF-1 levels, what are 2 important things to remember?
Definition
1. serum IGF-1 must be interpreted in light of values in normal sex and age matched subjects 2. IGF1 levels may be lowered in pts with malnutrition and protein insufficiency (consider nutritional status)
Term
how do we tx acromegaly?
Definition
1. surgical removal of adenoma (50% success) --> need multimodality rx 2. radiation (req mos to yrs for radiation to be effective therefore tx with medicine while wait for effects - only for ppl who cant/wont do surg or ppl w/unsuccessful surg) 3. meds (somatostatin analogs, growth hormone receptor antagonists, dopamine agonists)
Term
whats usually the first test performed in people suspected of having cushings syndrome?
Definition
overnight dexamethasone suppression test (1mg given at night, cortisol drawn in morn, cortisol <5mcg/dL r/o cushings, >5mcg/dL --> further testing)
Term
describe alcohol-pseudo-cushings syndrome?
Definition
alcohol abusers have many features suggestive. have elevated levels of usual diurnal variation and fail to suppress with screening overnight dexamethasone suppression test
Term
what do we need for definitive dx of cushings syndrome?
Definition
show plasma cortisol cannot be suppressed <5mcg/dL w/48 hrs of dexamethasone given in low dose every 6 hours (8 doses). urinary cortisol should fall <30mcg in a 24 hour collection
Term
how do we distinguish between cushings disease and other causes of cushings syndrome?
Definition
high-dose dexamethasone suppression test. (2mg q6hx8 doses). pts with CD WILL suppress plasma cortisol to <5mcg/dL, while pts with other causes will fail to suppress.
Term
what is the tx for cushings disease?
Definition
surgical removal (transphenoidal surgery). not cured?--> radiation, gamma knife therapy, bilateral adrenalectomy, med therapy
Term
3 causes of hypotonic polyuria
Definition
1. primary (excess water intake, normal) 2. hypothalamic (lack vasopressin) 3. nephrogenic (vaspressin levels high, but kidney unresponsive bc of defect in receptor response. can be congenital or caused by electrolyte abn like hypokalemia or hypercalcemia or drugs)
Term
how to dx diabetes insipidus
Definition
standard dehydration test (drink no fluid, record polyuria and weight --> 2 consecutive voided urines differ by <10% osmolality? and pt has lost 2% body weight? --> give 2 mcg desmopressin --> normals will have <5% increase in urine osmolality over next 2 hrs, and pts with DB insipidus will have increase >50%)
Term
what are the 3 forms of hereditary diabetes insipidus?
Definition
autosomal dominant central neurogenic diabetes insipidus (many mutations of the vasopressin gene); x-linked nephrogenic db insipidus (abn of the gene for vasopressin V-2 receptor in kidney); autosomal recessive nephrogenic diabetes insipidus (abn of aquaporin-2 water channel)
Term
what is essential hypernatremia
Definition
absence of osmoreceptor input, but intact volume receptor input. excrete excess hypotonic urine and do not sense thirst to replace fluid. dehydration --> vol receptors release vasopressin and pt maintains hypernatremia and concentrated urine
Term
what is triphasic diabetes insipidus?
Definition
after acute injury to neurohypophysis (i.e. trauma) --> section/contusion of posterior pituitary stalk --> disruption of vasopressinergic neurons and decreased release of vasopressin --> db insipidus. THEN disruption of blood flow to posterior pituitary--> necrotic posterior pituitary --> post pituitary releases stored vasopressin in uncontrolled manner --> max anti-diuresis --> hormone depleted --> back to db insipidus
Term
how do we tx pts with db insipidus?
Definition
water, desmopressin
Term
how can pts recover from diabetes insipidus alone?
Definition
hypothalamic db insipidus from trauma or tumor --> hypertrophy of remaining vasopressinergic neurons--> re-establish axons adjacent to capillaries in the hypothalamic suprasellar area
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