Endocrine Flashcards
Most common malignant tumor in neonates
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
when does the thyroid gland begin to develop?
3 weeks
develops from the median ENDODERMAL thickening in primitive pharyngeal floor at ~5-7 weeks
Development of T4
THYROXINE
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
development of T3
TRIIODOTHYRONINE
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
what does the fetus metabolize T4 to?
reverse T3
development of TSH
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
placental role in thyroid hormones
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
major source of circulating T3
T4
converted in the peripheral tissues
Thyroid hormone production
TRH (hypothalamus) –> anterior pituitary –> TSH synthesis and secretion
TSH (anterior pituitary) -> incr all steps in TH production
regulated by peripheral TH levels (mostly T4)
What decreases TBG
prematurity
glucocorticoids
malnutrition
liver disease (cant make proteins)
nephrotic disease (cant hold onto proteins)
congenital TBG deficiency
what decreases TBG binding affinity
phenytoin
most sensitive and specific test of hypothyroidism
TSH
IV dopamine can lead to transient dec in TSH
major findings in congenital hypothyroidism
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
AR organification defect with congenital 8th nerve abnormalities leaidn to deafness
goiter during childhood
Pendred syndrome
dx: +percholate discharge test
rapid loss of radioactive iodine from thyroid gland
types of TRAbs
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
maternal treatment for Grave’s
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
transient neonatal hyperthyroidism secondary to maternal grave’s disease presentation in utero
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
post natal presentation- infant affected by maternal grave’s disease
typically sx by 14 days of age
- can be earlier if no maternaltreatment
- can be later if maternal treatment
treatment for postnatal neonatal transient hyperthyroidism due to maternal grave’s disease
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
long term effects of untreated clinical hyperthyroidism
decreased growth
craniosynostosis
intellectual/developmental impairment
if early treatment, excellent outcome
adrenal cortex derived from
mesoderm
adrenal medulla derived from
neuroectodermal cells of neural crest
T/F
the fetal adrenal gland is larger than adult adrenal gland
TRUE
large inner fetal zone that involutes durig the first few months after birth
what does the adrenal medulla produce?
catecholamines- epi, norepi, dopa
what does the adrenal cortex produce?
sex hormones- zone reticularis
glucocorticoids - fasciculata
mineralocorticoids- zone glomerulosa
Hyperinsulinism lab values
how does diazoxide work to prevent hypoglycemia and treat hyperinsulinism?
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
