Endocrine Flashcards
when does embryologic devp of thyroid gland begin?
From which layer?
When does TRH start?
When does TSH production start and thyroid hormone production?
3 weeks
thyroid gland from endodermal thickening in primitive pharyngeal floor 5 - 7 weeks
TRH by 6 - 8 weeks
Fetal thyroid accumulate I by 8-10 weeks
TSH and thyroid hormone secretion by 12 weeks
Transitions of T4 and T3 - how amounts change in utero and then post natally
T4 - low until 18 - 20 wks (as hypothalamus and pituitary mature) -> increases with GA -> surge at birth 2/2 TSH surge -> peak 24 - 36 hours -> levels down over 1 - 2 weeks
T3 - low until 30 weeks when fetus can convert T4 to active T3 (mature type 1 deiodinase) -> surge at birth -> peak 24 - 36 hrs -> T3 levels increase post natally b/c of neonate’s ability to convert T4 to active T3
NOTE: fetal brain and pit T3 levels higher than serum
TSH and thyroid hormones in premature infant
Also… compare AGA term to SGA term re. TSH, fT4, T4, etc.
thyroid hormones post-natal
presentation of 3 beta hydroxysteroid dehydrogenase
EARLY in the steroidogenesis pathway – cannot convert pregnenolone to progesterone; 17 oH pregnenalone to 17 OH progesterone; DHEA to androstenedione –> small phallus, abnormal external male genitalia (underdeveloped)
Evaluation of under-virilized male
Electrolytes, LH, testosterone, DHT, FSH in 1st 24 hours, MIS (for testicular function)
what gene facilitates differentiation of gonads to testes?
SRY on Y gene
Sexual differentiation - when does it embryologically start?
When does virilization start in ebryo?
Sexual differentiation week 6 - 7
Virilization week 6 - 12
Match the following:
Embryologic origin - mosonephric duct, coelemic epithelium, genital tubercle, labiascrotal folds
with…
Wolffian duct
Mullerian duc
Corpus cavernosa or clitoris
Scrotum or labia majora
wolffian duct - from excretory mesonephric duct
mullerian duct - from coelemic epthelium
corpus cavernosum or clitoris - from genital tubercle
scrotum or labia majora - from labiascrotal folds
Review path of sexual differentiation and devp
Pre to post natal TSH, thyroid hormone
Osteopenia vs osteomalacia
Hormonal adjustments to Ca and Ph - in intestines, bone
Hormonal adjustments of PTH, calcitonin, vit D
Review adrenal steroidogenesis pathways
NB presents with ambiguous external genitalia, HTN, normal electrolytes, increased deoxycorticosterone and deoxycortisol concentrations.
Presumed diagnosis
Most appropriate management (eg rx)
11 beta hydroxylase deficiency (#2 common cause)
Low cortisol - cannot convert 11 deoxycortisol to cortisol
Low aldosterone - cannot covert deoxycorticosterone to corticosterone
Increased testosterone (alternate pathways)
NO salt wasting b/c deoxycorticosterone functions as a mineralcorticoid. SO manage by giving glucocorticoid replacement and eventual reconstructive surgery of abnormal female genitalia if desired
Expected male baby XY genotype. On exam, micropenis, urethral meatus at base. Testes palpable in inguinal canal bilaterally. FOB with a mutation in the DNA binding domain of the androgen receptor.
Mutation of the androgen receptor (AR) which is encoded on the X chromosome – lack of androgen signaling results in decreased virilization. Testosterone upregulated due to lack of gonadotropin releasing hormone inhibition by testosterone so HIGH levels.
Steroid profile of 21 alpha hydroxylase deficiency
Elevated
- Progesterone
- 17 OH progesterone, 17 OH pregnenolone
- Dehydroepiandrosterone -> androstenedione -> testosterone
- Renin
Decreased
- 11 deoxycorticosterone
- Deoxycorticosterone
- Aldosterone
Review other abnormal lab values of enzymes deficiencies in adrenal steroidogenesis pathway
