Endocrine

Question 1

Most common malignant tumor in neonates

Answer 1

Neuroblastoma

Derived from neural crest cells which migrate to form the adrenal medulla and sympathetic ganglion –> primary locus is abdomen

Presentation:
1. metastatic lesions: liver (65%) or subcutaneous (32%)
2. diarrhea, hypertension, tachycardia, myoclonus-opsoclonus, respiratory distress, jaundice, anemia
3. urinary catecholamine levels ELEVATED: homovanillic acid and vanillylmandelic acid

Question 2

Answer 2

Question 3

when does the thyroid gland begin to develop?

Answer 3

3 weeks

develops from the median ENDODERMAL thickening in primitive pharyngeal floor at ~5-7 weeks

Question 4

Development of T4
THYROXINE

Answer 4

low amts until ~ 18-20 = hypothalamus and pituitary matures in fetus

increase dramatically at birth following TSH surge

peak = 24-36 hrs then decrease over 2 weeks as TSH decreases

Question 5

development of T3
TRIIODOTHYRONINE

Answer 5

low until ~ 30 wks = fetus can convert T4 to active T3

increases dramatically at birth
peak = 24-36 hrs then continues to increase after birth

Question 6

what does the fetus metabolize T4 to?

Answer 6

reverse T3

Question 7

development of TSH

Answer 7

low amounts until 18-20 wks = hypothalamus/pituitary maturesd
increases proportionaly with GA

peak 30 min of age = extrauterine cold exposure = incr T4 + T3

levels dec over next 2 weeks

Question 8

placental role in thyroid hormones

Answer 8

placenta produces estrogens –> incr maternal thyroxine-binding globulin (TBG), T4/T3
placental produces hCG = induces mat T4/T3 (hCG is structurally similar to TSH)

EUTHYROID STATE MAINTAINED IN PREGNANCY

T4 –> rT3 –> baby
T3 –> T2 –> baby
TRH (small) –> baby
MOST IMPORTANT= iodide via transplacental transfer —> ACTIVE transport
Maternal TSH-rec stim/blocking IgG cross placenta

TSH DOES NOT CROSS THE PLACENTA

Question 9

major source of circulating T3

Answer 9

T4
converted in the peripheral tissues

Question 10

Thyroid hormone production

Answer 10

TRH (hypothalamus) –> anterior pituitary –> TSH synthesis and secretion

TSH (anterior pituitary) -> incr all steps in TH production
regulated by peripheral TH levels (mostly T4)

Question 11

What decreases TBG

Answer 11

prematurity
glucocorticoids
malnutrition
liver disease (cant make proteins)
nephrotic disease (cant hold onto proteins)
congenital TBG deficiency

Question 12

what decreases TBG binding affinity

Answer 12

phenytoin

Question 13

most sensitive and specific test of hypothyroidism

Answer 13

TSH

IV dopamine can lead to transient dec in TSH

Question 14

major findings in congenital hypothyroidism

Answer 14

prolonged jaundice > 7 days
large posterior fontanelle
puffy facies
umbilical hernia
macroglossia

long term effects:
delayed bone/body growth
mental deficiency –> delayed myelination and abnormal neuronal cell membrane synthesis
delayed puberty

tx = levothyroxine ASAP to prevent mental deficiency

Question 15

AR organification defect with congenital 8th nerve abnormalities leaidn to deafness
goiter during childhood

Answer 15

Pendred syndrome

dx: +percholate discharge test
rapid loss of radioactive iodine from thyroid gland

Question 16

types of TRAbs

Answer 16

TSH receptor STIMULATING (TSI)
- TSI binds to TSH rec on thyroid follicular cells –> incr TSH production
- if TSI > TBS = transient HYPERthryoid

TSH receptor BLOCKING (TBA)
- TBA gind to TSH on thyroid follicular cells –> block TSH production
- TSI < TBA = transient HYPOthyroidism

Question 17

maternal treatment for Grave’s

Answer 17

PTU
- use during 1st trimester –> preauricular sinus/fistula, urinary tract abnormalities, low fetal birthweight
- preferred agnet during first trimester

Methimazole
- use during first timester –> cutis aplasia, choanal atresia, GI defects
- preferred agnet after first trimester

Question 18

transient neonatal hyperthyroidism secondary to maternal grave’s disease presentation in utero

Answer 18

typically presents during 3rd trimester

fetal tachycardia
growth restriction
goiter - concern for esophageal obstruction
advanced bone maturation
craniosynostosis
increased risk of preterm birth
fetal cardiac failure/hydrops

Question 19

post natal presentation- infant affected by maternal grave’s disease

Answer 19

typically sx by 14 days of age
- can be earlier if no maternaltreatment
- can be later if maternal treatment

Question 20

treatment for postnatal neonatal transient hyperthyroidism due to maternal grave’s disease

Answer 20

methimazole = PREFERRED- inhibits thyroid peroxidase = dec TH synthesis

PTU = no longer preferred agent potential liver failure

Beta-blocker = inhibits peripheral conversion T4 –> T3

glucocorticoids: use if severe hyperthyroidism to dec TH secretion, block peripheral conversion of T4 to T3

Question 21

long term effects of untreated clinical hyperthyroidism

Answer 21

decreased growth
craniosynostosis
intellectual/developmental impairment

if early treatment, excellent outcome

Question 22

adrenal cortex derived from

Answer 22

mesoderm

Question 23

adrenal medulla derived from

Answer 23

neuroectodermal cells of neural crest

Question 24

T/F
the fetal adrenal gland is larger than adult adrenal gland

Answer 24

TRUE
large inner fetal zone that involutes durig the first few months after birth

Question 25

what does the adrenal medulla produce?

Answer 25

catecholamines- epi, norepi, dopa

Question 26

what does the adrenal cortex produce?

Answer 26

sex hormones- zone reticularis
glucocorticoids - fasciculata
mineralocorticoids- zone glomerulosa

Question 27

Hyperinsulinism lab values

Answer 27

Question 28

how does diazoxide work to prevent hypoglycemia and treat hyperinsulinism?

Answer 28

activates ATP sensitive K+ channels on the membrane of pancreatic beta cells –> promotes potassium eflux –> hyperpolarizes cell membrane –> prevents influx of calcium –> blocks the release of insulin

can cause pulmonary HTN