Endocrine Flashcards
Symptoms and signs of adrenal hemorrhage
- Mild—asymptomatic
- Moderate—hypertension (induced transient reactive hyperplasia), unconjugated hyperbilirubinemia
- Severe—hypotensive shock, severe anemia, mass
Risks are difficult delivery (especially if infant large/dystocia) and perinatal depression. (Like other highly vascular areas, is at increased risk from those stresses)
Clinical findings in panhypopituitarism
- hypoglycemia
- micropenis
- cholestasis
Clinical findings in hypothyroidism
- hypoglycemia
- cholestasis
- failure to thrive
(similar to panhypopituitarism, main difference is sexual development)
The system tested by a cortisol stimulation test
Hypothalamic-pituitary-adrenal (HPA) axis
Location and stimulants of ADH excretion
Posterior pituitary
Primary stimulant: high serum osmolality (>284 mOsm/kg)
Others: hypoxia, hypotension, acidemia
What gene is required for Sertoli cells, and what two hormones do those cells make?
SOX9
Anti-mullerian hormone and mullerian-inhibiting hormone
Sertolis are SOX9 fans and Mullerian-haters
What hormone is most responsible for external genitalia development?
Dihydrotestosterone (DHT)
Made from testosterone (via 5-alpha-reductase)
Hormone elevated in classic congenital adrenal hyperplasia (CAH)
17-hydroxyprogesterone (17-OHP)
Build-up product from 21-hydroxlyase deficiency (most common form of CAH)
Four “basic” laboratory abnormalities in congenital adrenal hyperplasia (CAH)
- Hyponatremia (salt-wasting from aldosterone insufficiency)
- Hyperkalemia
- Metabolic acidosis
- Hypoglycemia
Which would be potentially higher-risk and require “urgent” labs–a maternal history of hyperthyroidism or hypothyroidism
Hyperthyroidism–if mother has Graves disease, antibodies that activate TSH receptors can cross placenta and cause neonatal thyrotoxicosis
(Rare but possibly life-threatening, requires either maternal or cord antibody [TRAb or TSI] titers)
What are features of diabetes insipidus, and the main way to distinguish nephrogenic from neurogenic
- Polydipsia
- High serum osmolality
- Low urine osmolality
* In Neurogenic DI they can’t make ADH, their brain is dumb so ADH doesn’t respond to fluid restriction*
Laboratory findings in hypoparathyroidism
Low calcium, high phosphate, low PTH
This last point can help distinguish from pseudohypoparathryoidism
Pseudohypoparathyroidism facts
- Low Ca, high Phos, high PTH (insensitivity)
- Usually autosomal dominant, see short 4th/5th metacarpals and very round face
- Associated with inability to respond to TSH as well
What hormone is responsible for sexual differentiation in the first trimester (and where does it come from)
hCG from the placenta
(After 12 weeks the fetus’ hypothalamus starts making GnRH that then stimulates LH and FSH from the anterior pituitary)
The only thyroid-related compount that canNOT cross the placenta
TSH (thyroid stimulating hormone)
Most of T4 that crosses gets “deactivated” by conversion to rT3
The thyroid gland’s derived from what embryonal tissue
Endoderm
As are the lungs and foregut, compared to heart which comes from mesoderm
Fetal thyroid starts making thyroglobulin at ___ weeks and secreting thyroid hormone at ___ weeks
8 weeks and 12 weeks
Before 12 weeks, thyroid hormone (T3/T4) comes from mother
The thyroid hormone that’s most abundant in the fetus (up until term gestation)
rT3
Majority of maternal T4 is converted to inactive rT3 at placenta by deiodinase (fetus also has deiodinase)
What maternal hormone is structurally similar to TSH and responsible for increased maternal T3/T4 production?
bHCG
Whereas placental ESTROGENS are what causes increased production of TBG as well as T3 and T4
90% of thyroid hormone secreted by the thyroid is ____
T4
Converted to T3 (more potent, shorter half-life) in peripheral tissues and mainly kept intracellular
The most common cause of congenital hypothyroidism
Thyroid disgenesis (75%), i.e. aplasia, hypoplasia or ectopy
Only 10% 2-2 hypothalamic or pituitary issues
The best test to confirm thyroid dysgenesis
Radionuclide iodine123 scan “to assess degre of RAIU (radioactive iodine uptake)
Can test TBG, T3, TRH and antithyroid antibodies
How long should infants exposed to maternal Graves disease by monitored?
Minimum 4-6 weeks outpatient
- Majority of TSH receptor antibodies are STIMULATING, so will be hypERthyroid*
- Treatment can include PTU or methimazole, beta-blocker and in emergencies corticosteroids*
The two parts of the adrenals (cortex and medulla) make which products
CortEX: SEX and other hormones (glucocorticoids, mineralocorticoids)
Medulla: catecholamines (epinephrine, norepinephrine, dopamine)
Foremost cause of CAH (congenital adrenal hyperplasia) and lab findings
21-hydroxylase deficiency
Hyponatremia, hyperkalemia, VERY elevated 17-OHP, high testosterone
Linked to HLA type/mutations (like DM1 and Celiac)
Secondmost cause of CAH and laboratory findings
11 beta-hydroxylase deficiency
Elevated DOC (deoxycortisone) and 11-deoxycortisol, high testosterone
DOC has mineralocorticoid effects so not salt wasting
Hormone products of two testicular cell types
Sertoli cells: MIS (regression of Mullerian ducts)
Leydig cells: testosterone and INSL3 (insulin-like growth factor 3)
_L_uteinizing hormone, like both factors from _L_eydig cells, works on EXTERNAL genitalia
*Testosterone also stabilizes Wolffian ducts (internal)*
What should you always test for when you see hypospadias and undescended testes
Congenital adrenal hyperplasia (CAH)
What do 5 alpha-reductase and aromatase do?
5 alpha-reductase: testosterone to DHT (dihydrotestosterone, more active form)
Aromatase: testosterone to estradiol (and androstenedione to estrone)
Two problems that can cause a blind vaginal pouch in 46XY people
5 alpha-reductase deficiency (no DHT)
Androgen insensitivity syndrome (AIS) (can’t respond to DHT/T)
For undescended testes, who ultimately have more orchiopexies–term or preterm males?
TERM males
- Frequency of undescended tests is higher in premature infants (don’t descend until ~28 weeks)*
- 90% in preemies ultimately descend vs. 75% in term*
Glucose crosses the placenta via what mechanism?
Facilitated diffusion
“Fetal glucose is maintained entirely by placental transfer…using glucose transporters” (Brodsky 2010).
In what timeframe does glucagon surge after birth?
Minutes to hours
Along with catecholamine surge and insulin down-trend, all in response to being cut off from maternal glucose
“Critical labs” to be drawn when neonates are persistently hypoglycemic (and drawn WHEN hypoglycemic)
When glucose <40: insulin, growth hormone, cortisol (and PLASMA glucose [i.e. lab-run] since whole blood glucoses are less accurate)
The rate of fetal anomalies when diabetic control is achieved after conception
- 8%
vs. 2.5% if control’s achieved pre-conception
Three types of cardiac problems most common in infants of diabetic mothers (IDM)
Hypertrophic cardiomyopathy
VSD
dTGA
The posterior pituitary contains which hormones
Antidiuretic hormone (i.e. vasopressin)
Oxytocin
Hypothalamus PRODUCES these, posterior pituitary just stores
The hypothalamic-pituitary axis STARTS production at ___ weeks, but isn’t established until ____ weeks
12 weeks (same timeframe as fetal T4 production)
18 weeks is when axis is established (same timeframe as fetal [thyroid] being sufficient)
When does T4 peak after birth?
24-36 hours
In response to TSH surge 30min post-delivery (same as glucagon/catecholamine) 2-2 cold stress
