Endo

Question 1

When is fetal thyroid functional?

Answer 1

10-12 weeks
Begins thyroglobulin at 8 wks
Accumulates iodide at 10 wks
TSH 12 wks
Thyroid hormones 12 wks

Question 2

What is the highest type of thyroid in fetal life?

Answer 2

rT3
T4 low until rises at 18-20 wks
T3 low until rises ~30 wks
Both T3 and T4 rise 2-6x after birth

Question 3

What maternal thyroid hormone does not cross placenta?

Answer 3

TSH

All others do: T3, T4 (partial); TRH, TSH receptor antibodies

Question 4

What are components of T3? T4?

Answer 4

T3: monoiodotyrosine and diiodotyrosine
T4: two diiodotyrosine

Question 5

How are T3 and T4 different?

Answer 5

T3 more potent, intracellular, only 9% of secreted thyroid hormone
T4 90% of secreted thyroid hormone, extracellular, higher concentration in blood (50-100x), binds proteins more

Question 6

What is best test for hypothyroidism after the TSH surge?

Answer 6

TSH

Question 7

What is most common cause of congenital hypothyroidism?

Answer 7

Thyroid dysgenesis (75%): ectopic, aplasia, hypoplasia

Question 8

What is Pendred syndrome?

Answer 8

Autosomal recessive

Organification defect with congenital 8th nerve abnormality. Deafness, goiter

Question 9

What is incidence of neonatal hyperthyroidism if mom has Graves?

Answer 9

1-5%

Due to transplacental passage of TSH receptor stimulating antibodies and blocking antibodies

Question 10

How to treat neonatal hyperthyroidism?

Answer 10

1. Treat with propylthiouracil or methimazole
2. Beta blocker
3. Iodide (rapidly inhibit thyroid hormone release)
4. Glucocorticoids
   Ok to breastfeed

Question 11

What are 3 main pathways of adrenal cortex and what are end products?

Answer 11

1. Mineralcorticoids - aldosterone
2. Glucocorticoids - cortisol
3. Androgens/Estrogens - estrogen, testosterone

Question 12

What is most common cause of congenital adrenal hyperplasia?

Answer 12

21- hydroxylase deficiency

Leads to elevated 17-OH, lack of mineralcorticoid and glucocorticoid. Too much androgens

Question 13

What is second most common cause of congenital adrenal hyperplasia?

Answer 13

11- beta hydroxylase deficiency
Cant make cortisol or aldosterone (but can make aldosterone precursor so no salt wasting). Still too much androgens.
Dx: high deoxycorticosterone and 11-deoxycortisol

Question 14

What is difference between 17 alpha hydroxylase deficiency and 3 beta hydroxysteroid dehydrogenase deficiency?

Answer 14

17 alpha: ambiguous male genitalia, normal female but no secondary sexual traits. Low 17-OH progesterone and 17-OH pregnenolone
3 beta: small penis, severe hypospadias; high 17-OH pregnenolone, high 17-OH pregnenolone, DHEA

Question 15

How is cortisol made?

Answer 15

Corticotropin - releasing hormone (CRH, hypothalamus) -> ACTH (anterior pituitary) -> cortisol (adrenal cortex)

Question 16

What is the typical genotype of a true hermaphrodite?

Answer 16

Over half are 46, XX but majority raised as males

Question 17

Why is Kleinfelter syndrome infertile?

Answer 17

Atrophy of seminiferous tubules

Also have small genitals and gynecomastia (in 1/3, with inc risk of breast cancer)

Question 18

How does aromatase deficiency present?

Answer 18

Inability to convert testosterone to estradiol and androstenedione to estrone.
Ambiguous female genitalia, multicystic ovaries, tall, virilization at puberty, delayed bone age

Question 19

How does 5 alpha reductase deficiency present?

Answer 19

Males with ambiguous genitalia, small penis, blind vaginal pouch. Infertile. Testes descend at 12.
Females have normal phenotype.

Question 20

How does androgen resistance or insensitivity present?

Answer 20

Present as females, but have have hernias/labial masses. No uterus, testes present
High LH, normal FSH, high testosterone

Question 21

Which testicle is more likely to be undescended?

Answer 21

Right

Only 1/3 of cases are bilateral

Question 22

When do majority of testes descend?

Answer 22

By 9 months (90% of preterm infants, 75% of full term infants)
Orchiopexy by 1 year

Question 23

What hormone does anterior pituitary make? Posterior?

Answer 23

Anterior:
1. TSH
2. LH
3. FSH
4. Prolactin
5. GH
6. ACTH
Posterior:
1. Vasopressin (ADH) - stored and secreted here
2. Oxytocin (also stored and secreted)

Question 24

How do Ca, Mg, and Ph cross placenta?

Answer 24

Active transport

Question 25

When is the greatest time for Ca transfer to fetus? What is impact on fetal hormones?

Answer 25

3rd trimester

High serum Ca -> high calcitonin-> suppressed fetal parathyroid

Question 26

When are Ca levels the lowest after birth?

Answer 26

24 hours of life
Then PTH increases over first cpl days (peaks at 48 hours) and calcitriol also increases and stays constant after 24 hrs
* calcitonin increases immediately after birth

Question 27

What is calcitriol?

Answer 27

1, 25 vit D (active form)

Increases Ca and Ph intestinal absorption, also inc Ca from bone

Question 28

What does PTH do?

Answer 28

Increases calcitriol, increases Ca absorption from intestine and kidney. And release of Ca from bone

Question 29

What does calcitonin do?

Answer 29

Small inc in renal Ca/Ph excretion
Blocks release of Ca from bone
*opposite of PTH/calcitriol

Question 30

What is difference between hypoparathyroidism and psuedohypoparathyroidism?

Answer 30

Pseudo= tissue resistance to PTH
So PTH level will actually be high, but will have low calcitriol still.
Real hypoparathyroidism will have low PTH.