Endocrinology Flashcards
Most URGENT work up to obtain for ambiguous genitalia?
Electrolytes - think CAH because of decompensation risk
How are calcium, magnesium and phosphorous transported across the placenta?
A COW carries the 3 across the placenta via ACTIVE transport.
What is the cut off level for TSH to treat for hypothyroid?
> 40
MCC of neonatal hypothyroidism
Ectopic thyroid (dysgenesis)
Goal of orchipexy if undescended testes?
Increase sertoli cells, increase germ cells and increase testicular volume. Reduce risk of testicular cancer
When does anatomic development of the thyroid gland begin?
3 weeks
Where does the thyroid gland form from?
Midline endodermal thickening in the primitive pharyngeal floor at 5-7 weeks
When does the fetal thyroid gland start secreting thyroid hormones?
12 weeks
When does the TSH surge occur and what is it in response to? When do levels decrease?
Peaks at 30 min age, due to extrauterine cold exposure
Levels decrease over 1-2 weeks postnatally
When does the T4 surge occur and what is it in response to? When do levels decrease?
Peaks at 24-36 hours after birth, in response to TSH surge.
Levels decrease over 1-2 weeks (follows TSH)
When does the T3 surge occur and why?
Peaks at 24-36 hours after birth due to neonate’s increased ability to convert T4 to T3.
How much do the thyroid hormones cross placenta:
TRH
TSH
T4 and T3
TRH is produced in small amounts during pregnancy and crosses the placenta
TSH does NOT cross the placenta
Placenta partially degrades T3 and T4 (partially permeable), reverse T3 is in the highest concentration in the fetus
Most common cause of congenital hypothyroidism?
Primary -> permanent type due to thyroid dysgenesis. Ectopic thyroid most common
Features of Pendred syndrome?
Autosomal recessive
CN 8 deafness
Thyroid hormone dysgenesis
How is glucose transported across the placenta?
Facilitated diffusion using glucose transporters
What are the 4 main substrates for gluconeogenesis??
- Lactate/pyruvate
- Gluconeogenic amino acids (alanine most important)
- Glycerol
- Propionic acid
When does glycogen storage occur in the liver?
During 3rd trimester
Which thyroid hormone does NOT cross the placenta?
TSH
Which hormones are produced in the anterior pituitary?
GH, TSH, ACTH, LH, FSH and prolactin
Which hormones are produced in the posterior pituitary?
Oxytocin and ADH
Which hormone promotes calcium and phos deposition in the fetus?
Maternal estrogen
Because of fetal high calcium, the fetal PTH is suppressed
Physiologically active form of calcium?
iCal
Tightly regulated by an interaction of PTH and 1,25-OH-D
For an infant born to a mother with Graves, when should TSH and fT4 levels be obtained?
3-5 days of age, repeat at 10-14 days
Which hormone needs to be tested with infantile hemagiomas and why?
Thyroid
Infantile hemangiomas undergo consumptive hypothyroidism during their proliferative phase
Cause of hypercalcemia in subcutaneous fat nodule
unregulated increase in the extrarenal release of 1,25-dihydroxy vitamin D during necrosis of granulomatous fat cells, leading to an increased intestinal absorption of calcium.
