Endocrine Flashcards
Which Thyroid hormone is highest in fetus?
Reverse T3
(fetus metabolizes T4 to rt3)
When can fetus begin converting T4 to t3?
About 30 weeks gestational age
How does fetus maintain iodide needed for thyroid hormone production?
transplacental transfer
Why do maternal T4 and T3 increase in pregnancy?
hcg structurally similar to TSH
Does TSH cross placenta?
No
Describe steps of thyroid hormone production
TRH made in hypothalamus, acts on anterior pituitary to release TSH, TSH acts on thyroid gland
Why is Free T4 a good measure of thyroid function?
only free form can enter cells
What decreases TBG?
Essentially anything that makes you sick, prematurity, or glucocorticoids.
What does iodine exposure due to T4 levels?
decreases
Why do neurologic deficiencies manifest with hypothyroidism?
delayed myelination and abnormal neuronal cell membrane synthesis.
What is medication used for Graves in first trimester?
Propylthiouracil
What is medication used for Graves in third trimester?
Methimazole
avoid during first trimester due to cutis aplasia
Postnatal management of Hyperthyroidism?
Methmiamzole, PTU (2nd choice, due to liver failure), Beta blocker (inhibits T4 to t3), iodine (stops TRH), Glucocorticoids, block T4 to 3
Pathway of cortisol production
Hypothalamus secretes CRH, induces anterior pituitary to secrete ACTH, which than leads to production by adrenal gland
Cortisol deficiency would lead to
Hypoglycemia, hypotension, anemia
What is function of cortisol?
- Induces gluconeogenesis and antagonizes insulin
- Increases CA and phosphate release from bone
- Decreases inflammation and suppresses immune system
- Inhibits ADH, increases RBC production
21 hydroxylase deficiency leads to what?
Increase 17-OHP
increased testosterone production
salt wasting and hypotension because of aldosterone deficiency
(17-OHP can’t be converted to 11 DOC)
Laboratory findings CAH
hyponatremia, hyperkalemia, hypoglycemia, and elevated 17-OHP
In 11 Beta Hydroxylase deficiency why is there no salt wasting?
DOC can still function as mineralocorticoid
How do you diagnose 11 Beta Hydroxylase deficiency
High DOC and 11-deoxycortisol levels with increased response to ACTH
Maternal exposure to fetal androgens (female fetus) what happens before 13 weeks gestation
After 13 weeks gestation
Before 13, posterior fusion of vagina, scrotilization of labia
After, clitoromegaly
What is 5 alpha reductase deficiency?
AR disorder can’t convert testosterone to dihydrotesterone
there is absence of Mullerian structures, and presence of Wolffian (just poorly developed)
What causes hydrocele?
persistence of processus vaginalis, which usually involutes
communicating (increases with increase abdominal pressure) vs non-communicating
Do you see alkalosis or acidosis in CAH?
Acidosis due to deficiency of aldosterone
Explain salt wasting crisis
deficiencies in both glucocorticoid and mineralocorticoid activities
glucocorticoid deficiency can cause hypotension and hypoglycemia (which can lead to siezures)
mineralocorticoid deficiency can ause worsening urinary salt loss, dehydration and potassium retention.