Endo Flashcards
When does the fetal thyroid gland develop?
3 weeks gestation
From what tissues does the thyroid gland develop?
Endoderm
- pharyngeal floor
When do thyroid follicles develop and begin thyroglobulin production?
8 weeks gestation
Iodide can accumulate in the fetal thyroid at ___ weeks.
10 weeks
When does the fetal pituitary gland produce TSH?
When does the fetal thyroid gland produce thyroid hormones?
12 weeks
When do T4 levels surge?
18-20 weeks (at hypothalamus and pituitary maturation) and again at birth
Peak levels at 24-36 hours of age
When do T3 levels increase?
30 weeks (T4 to T3 via Type I deiodinase)
Where are T3 levels highest in the fetus?
Brain and Pituitary
When do T3 levels peak?
Dramatic increase at birth–> 24-36h due to increase T4-> T3 conversion
The fetus metabolises t4
Reverse T
TSH levels are low until _____ then increase with age
18 to 20 weeks
Cold exposure at birth causes TSH levels to
Dramatically increase at 30 minutes of age
In terms infants T4 levels increase due to _______ while in preterm infants T4 ________ at birth
Dramatic TSH surge
Blunted TSH surge and loss of maternal T4
Placental estrogens cause increase in
Maternal thyroxine bonding globulin, T4, T3
HCG causes increase in _____ due to HCG mimic of _____
T4, T3
TSH
Placental conversion of ______ to ______ allow transfer to fetus
T4, rT3
T3, T2
TSH is produced by
Anterior pituitary
TRH is produced by
Hypothalamus
90% of the thyroid hormone secreted from the thyroid is
T4
9% T3
1% rT3
Congenital hypothyroidism is primarily caused by
Thyroid dysgenesis (75%)
Thyroid dyshormonogenesis (10%) Transient hypothyroidism (10%) Hypothalamic -pituitary defect (5%)
Transient hypothyroxinemia of prematurity affects ____% of infants _______
50%
<30 weeks
Congenital hypothyroidism with 8th nerve abnormality causing deafness could be due to _____, inherited _______
Pendred syndrome
Autosomal recessive
Thyroid screening for congenital hypothyroidism should happen at ______ age
36-72h
1-5% of infants born to mother’s with Graves disease will have
Congenital hyperthyroidism
Hyperthyroidism due to maternal Graves disease is caused by
Placental transfer of TSH receptor-stimulating antibodies
TSH receptor-blocking antibodies
If stimulating» blocking—> transient hyperthyroidism
If blocking»> stimulating–> transient hypothyroidism
Transient thyroid disregulation due to maternal Graves disease can present at _____ and last for _____ due to antibody half life.
10 days
8-20 weeks
Infants born to mother’s with Graves disease with our without thyroidectomy should be tested for
TSH receptor antibodies (TRAbs)
Adrenal cortex is derived from ______ and medulla is from ______
Mesoderm
Neuroectodermal cells of neural crest
Adrenal glands form from
5-8 weeks
Cortex cells 5-6 weeks
Medulla 7-8 weeks
Adrenal medulla produces
Catecholamines
Epinephrine
Norepinephrine
Dopamine
Adrenal cortex produces
Mineralocorticoid
Glucocorticoids
Sex hormones (DHEA)
Most common cause of congenital adrenal hyperplasia
21 hydroxylase deficiency
Aldosterone deficiency, cortisol deficiency, and increased testosterone with salt wasting is associated with
21 hydroxylase deficiency
21 hydroxylase deficiency presents
Normal male+/- salt wasting, precocious puberty, advanced bone age
Ambiguous female, salt wasting, virilization, hirsutism
Elevated 17-OHP, abnormal ACTH stim response
Second most common cause of Congenital adrenal hyperplasia is
11 beta hydroxylase deficiency
Impaired conversion of 11 deoxycortisol causes
Cortisol deficiency
Increased testosterone
Aldosterone deficiency without salt wasting
11- beta hydroxylase deficiency
Normal male/ambiguous female with high BP is ______ while ambiguous male/normal female without secondary sex characteristics with high BP is _______
11 beta hydroxylase deficiency
17 alpha hydroxylase deficiency
Normal BP with salt wasting with ambiguous genitalia in both sexes is
3 beta hydroxy steroid dehydrogenase deficiency
Cortisol is produced by
CRH from hypothalamus–>
ACTH from anterior pituitary –>
Zona faaciculata/reticularis of adrenal glands–> cortisol
Cortisol causes
Gluconeogenesis Increased RBC production Decreased inflammation Immune system suppression Calcium/phosphorus release from bone Decreased ADH Lipolysis Vascular catecholamine response
46,XX ambiguity
21-hydroxylase
11-beta hydroxylase
3-beta hydroxysteroid dehydrogenase deficiency
Maternal androgen/progesterone
Aromatase deficiency
46, XY ambiguity
17- alpha hydroxylase
3-beta hydroxysteroid dehydrogenase deficiency
5 alpha reductase deficiency (AR)- late virilization
Androgen resistance/insensitivity
Hypospadias + bilateral undescended testes= eval for
CAH
Cryptorchidism can be associated with
Hypothalamic-pituitary testicular axis abnormalities Abdominal defects Meningomyelocele Trisomy 13, 18 Noonan Smith Lemli Opitz Familial
Cryptorchidism is usually
Unilateral (2/3)
Right» left
Inguinal
Euglycemia is maintained at birth with
Increasing glucagon
Decreased insulin
Catecholamine–>glycogenolysis, gluconeogenesis, lipolysis, ketogenesis
Pituitary gland develops from
Ectoderm
Anterior pituitary develops from
Rathke’s pouch
Posterior pituitary develops from
Forebrain
Anterior pituitary function:
Hormone secretion (TSH, LH, FSH, prolactin, GH, ACTH, pro-opiomelanocortin)
Posterior pituitary function:
Store and secrete anterior pituitary gland hormones
Hypothalamus hormones:
Vasopressin (ADH)
Oxytocin
HPA axis functions at
18 weeks
Panhypopituitarism should be treated with
Growth hormone
Increased osmolality at osmoreceptors
OR
Hypovolemia at cardiovascular volume receptors –>
increased ADH secretion–>
Water reabsorption
ADH causes water reabsorption by
Increasing distal nephron permeability
Vasoconstriction
Decreased renin
Increased ACTH
ADH fails to cause water reabsorption in
Nephrogenic DI
RAAS pathway
Renin–>
Angiotensin I –>
Angiotensin 2 –>
Aldosterone/ADH
Transplacental transfer of Ca, phos and mag is by
Active transport
Maternal ______ increases fetal Ca availability by _____
PTHrP
Increased calcitriol production –> maternal intestinal calcium absorption
Calcium and phosphorous are reabsorbed in the neonatal
Kidney, proximal tubule (>90%)
____ and ____ hormones increase calcium and phosphorous release from the bone
Cortisol
Thyroid hormone
To increase Ca, PTH levels ____ and phosphorous levels are _____
Increase
Decreased
Hypocalcemia can cause ______ in EKG
Prolonged QT
Hypoparathyroidism and infantile hypophosphatemia cause
Hypercalcemia
Hypomagnesemia can cause ____ on EKG
Prolonged QT
Decreased bone matrix suggests
Osteopenia
Decreased bone mineralization suggests
Osteomalacia
Widened growth plates with fraying occurs in
Osteomalacia
Bone disease of prematurity has low _____ and high _____
Phosphate
1, 25 OH D
PTH
+/- calcium, alk phos
Pseudohypoparathyroidism is marked by
Decreased Calcium
Increased phosphorus
High PTH**
In primary hypoparathyroidism, labs are
Decreased calcium
Increased phosphorous
Low PTH**