B6.076 Endocrine Myopathies

Question 1

hypothyroid myopathy pattern

Answer 1

slow, progressive proximal weakness
fatigue
cramps

Question 2

neuro tests of hypothyroidism

Answer 2

EMG often normal
carpal tunnel seen on nerve conduction studies
length-dependent peripheral neuropathy may be seen

Question 3

lab findings in hypothyroidism

Answer 3

TSH high
T3 low
T4 low

Question 4

thyroid stimulation loop

Answer 4

decreased T3 and T4 in the blood stimulate…
hypothalamus to release TRH which stimulates…
pituitary to release TSH which stimulates….
thyroid to release T3 and T4 which inhibits….
hypothalamus

Question 5

type 1 fibers

Answer 5

slow twitch
oxidative
low strength, low fatigability

Question 6

type 2a fibers

Answer 6

fast twitch a
oxidative & glycolytic
high strength, moderate fatigability

Question 7

type 2x fibers

Answer 7

fast twitch x
glycolytic
high strength, high fatigability

Question 8

what is a muscle core

Answer 8

zones of myofibrillar disarray lacking in oxidative and phosphorylase enzyme activity

Question 9

risk to parathyroid glands during thyroid surgery

Answer 9

at risk of trauma, devascularization, or removal

Question 10

pathological changes with parathyroid removal

Answer 10

decreased PTH
inability to maintain serum Ca
decreased 1,25 vit D
reduced intestinal C absorption
abnormal mobilization of Ca from bone
high urinary Ca excretion
--->>> hypocalcemia

Question 11

changes in phosphate in hypoparathyroidism

Answer 11

increased serum phosphate

proximal tubular effect of PTH to promote phosphate excretion is lost

Question 12

why does hypoparathyroidism have a prolonged latency period

Answer 12

may have decreased parathyroid reserve, not complete dysfunction
increased stress on glands may precipitate symptoms (pregnancy for example)

Question 13

Chvostek sign

Answer 13

tap on facial nerve anterior to the ear

twitching of ipsilateral facial muscle is a positive test

Question 14

Trousseau sign

Answer 14

inflate BP cuff over systolic BP for 3 min

painful carpal muscle contractions and spasms are a positive test

Question 15

what do Chvostek and Trousseau signs indicate

Answer 15

latent tetany secondary to hypocalcemia

Question 16

pathophys of hypertension in Cushing

Answer 16

increased R-A-A
increased mineralocorticoid activity
increased sympathetic nervous system
increased vasoconstriction

Question 17

pathophys of atherosclerosis in Cushing

Answer 17

dyslipidemia
inflammation
insulin resistance
impaired glucose tolerance
DM
visceral obesity

Question 18

cardiac remodeling in Cushing

Answer 18

LVH
changes in wall thickness
myocardial fibrosis

Question 19

pathophys of cardiac arrhythmias in Cushing

Answer 19

hypokalemia

Question 20

thrombosis diathesis in Cushing

Answer 20

increased VIII, vWf, platelets, fibrinogen, and PAI-1

Question 21

cause of obesity in Cushing

Answer 21

unclear
increase in appetite
lipogenic effects of hyperinsulinemia caused by cortisol excess

Question 22

cause of striae in Cushing

Answer 22

subQ fat deposition which stretches the skin and ruptures the subdermal tissues

Question 23

major causes of Cushing

Answer 23

ACTH secreting pituitary adenoma
ectopic ACTH production
functioning adrenocortical adenoma / carcinoma
long term high dose exogenous glucocorticoid intage (iatrogenic)

Question 24

p-a axis

Answer 24

hypothalamus releases CRF which stimulates….
anterior pituitary to release ACTH which stimulates….
adrenal cortex to release cortisol which increases….
blood glucose, blood pressure, amino acids & inhibits hypothalamus

Question 25

how to demonstrate pathologic hypercortisolemia

Answer 25

free cortisol in 24 hour urine

overnight 1 mg dexamethasone suppression test

Question 26

steps in diagnosis of Cushing etiology

Answer 26

1. demonstrate pathologic hypercortisolemia
2. distinguish ACTH independent disease from ACTH dependent disease
3. determine anatomic localization of the ACTH source

Question 27

free cortisol 24 hour urine

Answer 27

outpatient
most sens and spec screening for Cushing
rarely normal in Cushing

Question 28

overnight 1 mg dexamethasone suppression test

Answer 28

lack of normal suppression by exogenous corticosteroid of adrenal cortisol production
in normal individuals: cortisol < 5
in Cushing: cortisol > 10

Question 29

how to differentiate pituitary or ectopic ACTH secretion

Answer 29

high dose dexamethasone suppression test

Question 30

anatomic localization of ACTH methods

Answer 30

MRI
thin section CT
IPSS
CSS

Question 31

rhabdo findings on biopsy

Answer 31

marked type 2 atrophy

Question 32

changes in myoglobin with rhabdo

Answer 32

increases rapidly following muscle injury and cleared quickly through renal excretion
normal level within 24 hours

Question 33

changes in CK with rhabdo

Answer 33

rises 2-12 hours after onset of muscle injury

peaks at 3-5 days after injury and declines over 6-10 days

Question 34

results of unaccustomed physical exercise that can lead to increased intracellular Ca

Answer 34

sarcolemmal and SR injury
increased cellular permeability to sodium
failure of energy production (Na+/K+ ATPase and Ca2+ATPase dysfunction)

Question 35

results of increased intracellular Ca

Answer 35

activation of Ca-dependent proteases and phospholipases
destruction of myofibrillar, cytoskeletal, and membrane proteins
muscle contraction

Question 36

symptoms of rhabdo

Answer 36

leakage in circulation: Ca, K, P, urate, aldolase, myoglobin, CPK, lactate dehydrogenase, aspartate transaminase
renal failure
blood clotting
cardiac arrhythmias

Question 37

CYP3A4 relationship to statins

Answer 37

oxidizes statins allowing their excretion

many drugs inhibit this CYP, reducing oxidation and resulting in greater bioavailability

Question 38

fibrate relationship to statins

Answer 38

inhibits phase 2 metabolism of statins (normally responsible for further metabolism of the statin for excretion out of the body)
fibrates cause oxidized statins to stay in the body and exert their inhibitory effect