Endocrine Flashcards
(95 cards)
1
Q
What tissue does the thyroid gland develop from?
A
endoderm
2
Q
What part of the kidney does ADH act on?
A
late distal tubule, cortical and medullary collecting ducts; acts by increasing the cortical and medullary collecting tubules to water and it is the primary determinant of water excretion in the kidney
3
Q
This presents with wieght gain due to fluid retention, hyponartremia, higher urine osmolality, low plasma osmolality, decreaased urine output
A
SIADH; Tx water restriction
4
Q
presents with increased UOP, dehydration, FTT. Labs show increase Na, hypotnic urine in the presence of serum hypertonicity, increased Ca, decreased K
A
nephrogenic DI, Tx with hydration, thiazdies to decrease urine concentrating ability with K supplement as needed
5
Q
Elevations in these 3 nutrients can cause factitious hyponatremia
A
hyperlipidemia, hyperproteinemia, hyperglycemia
6
Q
how does acidosis and alkalosis affect potassium?
A
acidosis can lea to hyperkalemia (for each 0.1 decrease in pH there is an increase in K by 0.6 mEg/L) and alkalosis can lead to hypokalemia
7
Q
When does TSH in the fetal pituitary gland begin?
A
12 weeks
8
Q
When are thyroid hormones secreted for the fetal thyroid gland?
A
12 weeks
9
Q
When do thyroid follicles form and begin thyrglobulin production?
A
8 weeks
10
Q
When can the fetal thyroid gland start to accumulate iodide?
A
10 weeks
11
Q
Why do T4 levels drop significantly after birth in preterm infants?
A
blunted postnatal TSH surge, loss of maternal T4 placental contribution and/or thyroid suppression from acute illness
12
Q
How is the placenta involved in thryoid function of the mom?
A
placenta produces estrogens that increase maternal TBG,T4 and T3. The placenta produces hCG which induces maternal T4 and T3 production because it is structrually similar to TSH. Placenta degrades maternal T4 to rT3 and maternal T3 to T2. T3 and T2 cross over to the fetuss
13
Q
What thyroid compounds cross the placenta?
A
TSH- receptor stimulating and blocking antibodies, iodide, TRH (small amt), T3 and T4
14
Q
What thyroid hormone does not cross the placent?
A
TSH
15
Q
What is the most common cause of congenital hypothyroidism?
A
thyroid dysgenesis (~75%)
16
Q
This syndrome manifests as a failed hearing screen and, abnml newborn screen, elevated TSH. Total T4 and free T4 may be normal to high
A
Pendred syndrome- AR organification defect with congenital 8th nerve anormality leading to deafness
17
Q
labs show normal to low TSH, low Total T4 and free T4. NBS may be normal
A
central hypothyroidism
18
Q
abnml NBS, elevated TSH and low free T4 and total T4
A
congenital hypothroidism
19
Q
abnml NBS, elevated TSH, normal to high T4 and free T4
A
thyroid hormone resistance
20
Q
normal to high TSH, normal to low Free T4 and total T4 and potentially normal NBS
A
transient hypothyroidism (drug induced, prematurity, illness, surgery)
21
Q
A newborn has an enlarged anterior fontanelle, large tongue, prolonged jaundice, delayed passage of meconium, hypotonia, hypothermia. Dx?
A
congenital hypothroidism; note: may have a goiter if the etiology is iodide transport defect, organification defect, thyroglobulin abnormnalities, or deiodinase deficiency
22
Q
What tissue is the adrenal cortex derived from?
A
mesoderm
23
Q
What tissue is the adrenal medulla derived from?
A
neuroectodermal cells of the neural crest
24
Q
What hormones are produces by the adrenal medulla?
A
catecholamines (epi, norepi, dopa)l the medulla is in the middle of the adrenal gland
25
What hormones are produces by the adrenal cortex
mineralocorticoids, glucocorticoids, sex hormones (Glomerulosa, fasiculata, reticularis)
26
What is the second most common cause of CAH?
11 beta hydroxylase def; esp in Arab and middle east Jewish population
27
in the male, what stuctures are derived from the Wolffian duct?
the duct is derived from the excretory mesonephros duct; the duct become the epididymus, vas deferens, ejaculatory duct, and seminal vesicles
28
In the male, what do the urethral folds do?
they fuse and form the corpus spongiosum and the penile urethra
29
In the male, what does the genital tubercle become?
corpora cavernosa or the penis/phallus
30
In the male, how does the scrotum form?
the labioscrotal folds fuse and it becomes the scrotum; local conversion of the testosterone to DHT by 5 alpha reductase leads to labioscotal fusion
31
What 2 important hormones do the testes make?
testosterone and Mullarian inhibiting substance; testosterone stabilizes the Wolffian duct and helps with differentiation of the external male genitalia and MIS cuases regression of the Mullerian ducts
32
What tissue makes the Mullerian duct and what structures does the Mullerian duct form?
Mullerian duct aka paramesonephric duct is derived rom the coelomic epithelium; develops into the fallopian tubes, uterus, cervix, and upper third of the vagina
33
In the female, what happens to the urethral folds and what do they become?
they do not fuse and form the labia majora
34
What does the genital tubercle become?
clitoris
35
in the female, what happens to the labioscrotal swellings?
they do not fuse and they form the labia majora
36
In Turner's syndrome, is the deleted chromosome maternal or paternal?
paternal, that's why there is no increased risk with advanced maternal age
37
What hormone promotes testicular development?
insulin- like growth factor 3
38
Do patients with Turner's develop secondary sex characteristics?
no, and the majority are infertile but they do have normal female external genitalia
39
Male with hypogonadism, infertility, and gynecomastia. Name the Dx and explain why there is infertility
47, XXY= Klinefelter synderom- infertile because of atrophy of the seminiferous tubules;
40
If an infant with Klinefelter's that has gynecomastia, does the breast tissue need to be removed and why?
yes- at increased risk for breast cancer
41
Name the 3 disorders that cause an undervirilized male due to a defect in androgen biosynthesis
3 beta hydroxysteroid dehydrogenase deficiency type 2, 17 beta hydroxysteroid dehydrogenase def, 5 alpha reductase def
42
What diagnosis is due to androgen resistance and creates and undervirilzed male?
angroden insensitivity
43
Male with ambiguous genitalia, with normal Wolffian structures and absent Mullerian structures, small phallus, urogenital sinus with perineal hypospadius and a blind vaginal pouch
5 alpha reductase deficiency, aka testes at 12 due to virilization and descent of testes into the labial location at the time of puberty
44
In 11 betahydroxylase deficiency, what two processes adrenal cortex don't happen?
deoxycorticoserone does not get converted to aldosterone and 11 deoxycortisol doesn’t get converted to cortisol
45
full terrm infant from Saudi arabia is noted to have ambigious gentalia and elevated BP. Labs show normal electrolytes and elevaated serum androgens and deoxycorticosterone. Dx?
11 beta hydroxylase def; commonly seen in Arab and middle east Jewish population
46
1 week old with intracranial hemorrage. High urine output, hypernatremia, hyperchloremic metabolic alkalosis, low K. Elevated serum osmolality and decreased urine osmolality. What will happen if you give ADH?
decreased in serum osmolaltity and increase in urine osmolality
47
This hormone is secreted in response to low serum calcium. It stimulates the activity of renal 1 alpha hydroxylase increasing the active form of Vit D and indirectly increase intestinal Ca and Phos absoprtion
PTH
48
how does PTH act on the kidney?
increases renal Ca absoprtion and decreases renal phos absorption. It also increases renal calcitriol production
49
How does PTH act on the bones?
acts directly on the bones by mobilizing calcium and phos
50
What percent of infant's born to mothers wth Graves disease will be clinically affected?
1%
51
What happens to reverse T3 postnally?
They decrease because of increased action of doiodnase and as well as loss of placental deiodinase D3
52
Why are IDM infants surfactant deficient?
the mechanism may result from increaed fetal insulin inhibitory action on fibroblast-pnemocyte factor, which normally acts on type II alveolar cells to produce surfactant
53
Why are IDM infants hypocalcemic?
there is a delay in neonatal parathyroid hormone surge due to urinary magnesium losses, which can decease PTH secretion this resulting in hypocalcemia
54
Are the genitalia of female infants with 5 alpha reductase normal?
yes
55
What enzyme deficiencies cause an overvirilzed female?
CAH (21-OH def, 3 B-OH dehydrogenase def, 11 B OH def), aromatase def, maternal androgen and progesterone therapy during weeks 8-13 of pregnancy; adrenal virilizing tumor, gestational hyperandrogenism (mother with virilization during pregnancy)
56
What are will the labs for a baby with CAH due to 21 OH deficiency show?
elevated 17 OH Progesterone that continues to be elevated after ACTH stim is done; males can present at 2 weeks of life with low Na, low Cl and high K and vomting and dehydration
57
What will the labs for a baby with 11 beta hydroxylase deficiency show?
increased deoxycorticosterone and increased deoxycortisol
58
What will the labs for a baby with 17 alpha hydroxylase deficiency show?
elevated deoxycorticosterone and corticosterone, low 17 OH progesterone and low 17 OH pregnenolone
59
What will the labs for baby with 3 beta hydrosteriod dehydrogenase defiency show?
elevated 17 OH pregnenolone, pregnenolone, and dehydroepiandrosterone
60
What is hyperglycemia in a preterm neonate correlated with?
stress and septicemia
61
Preterm infants with hyperglycemia have glycosuria. Is this associated with osmotic diuresis?
No. Preterm infans with hyperglycemia have glycosuria that is NOT a/w osmotic diuresis.
62
Which hormone contributes to the development of macrosomia in IDM infants?
insulin like growth factor-1 and insulin-like growth factor binding protein-3
63
What factors contribute to hyperglycemia in the preterm neonate?
early and high rates of intralipid infusions (leads to high FFA that promote gluconeogenesis which leads to glucose production); insuffient insulin secretion in preterm and growth restricted neonates; lack of feedings leads to diminshed incretin secretion (incretin is a hormone that promotes insulin secretion from the pancreas)
64
Are growth restricted infants at risk for hyperglycemia, hypoglycemia or both?
both
65
Why does an infant < 30 weeks have low total T4 and normal TSH?
total T4 is low due to low TBG, but free T4 may be normal; decreased stores of thyroid iodine, increased production of rT3 b/c of illness with correspondingly lower amt of T4, blunted post-natal TSH surge
66
What is the most common presentation of an infant with congenital hypothyroid at birth?
aymptomatic in 90%; note if BOTH mom and fetus are hypothyroid, most infants will have permanent coginitive delay
67
What is the most common cause of maternal-fetal hypothyroid world-wide?
iodine deficiency; note both iodine deficiency and excess can lead to hypothroidism
68
what medications can inhibit TSH secretion and lead to depressed T4 ?
dopamine, steroids, possibly caffiene inhibit TSH secretion; maternal PTU or methimazole
69
In SGA infants, how does the TSH and free T4 compare to AGA infants?
SGA infants have a significantly higher TSH surge and lower total and free T4 compared to AGA infants. This may be due to in utero malnutrition, fetal hypoxia and acidemia
70
What is the dominant thyroid hormone in neonatal life?
T3. After birth, TSH secretion increases --> T4 increases, Deiodinase 1 in fetal and placental tissue is activated and converts T4 to T3. After birth when D3 is no longer present, concentrations of rT3 significantly decrease
71
During times of critial illness among preterm infants, what thyroid hormone is increased?
rT3; during illness, D1 is decreased --> decreased conversion of free T4 to T3. Inactive D3 im turn converts T4 to rT3 which is why concentrations of T4 are lower during illness
72
In fetal life, what is the dominant thyroid hormone?
rT3 (starting at 20 weeks)
73
How does fat necrosis affect calcium levels?
increases Ca; hypercalcemia results from increased production of 1,25 OH vit D by the granulomatous lesions which increases intestinal absorption of Ca
74
DDX for hypomagnesemia
amphothericin B, maternal illness like DM or Pre-E, IUGR, prematurity, malabsorption, chronic diarrhea, liver dz, perinatal depression. Presents with irritability, tremors, muscle weakness, seizures
75
What are common non-specific findings in infants with hypopituitarism?
prolonged jaundice, hypothermia, lethargy, poor feeding, constipation.
76
Which hormon contributes most to phallic enlargement and testicular descent?
fetal LH; in the first trimester, testosterone production from the Leydig cells is drive by placental hCG. Fetal LH secretion increases during the second trimester and stimulates phallic enlargement and testicular descent
77
What structures are present in a female infant with androgen insensitivity?
normal female genitalia; but may have unilateral or bilateral inguinal hernias or labial masses, cryptorchidism, blind vaginal pouch, hypoplastic labia majora, NO UTERUS OR OVIDUCTS, underdeveloped Wolffian structures; labs show elevated LH, normal FSH, increased testosterone
78
What are the 2 main causes of an undervirilzed male?
decreased testosterone production or androgen insensivity
79
True or false. Because DHT is the primary hormone responsible for differentiation of male external genitalia, patients with 5 alpha reductase deficiency will have various degrees of ambiguous genitalia, ranging from a blind vaginal pouch to mild hypospadius with a bifid scrotum
TRUE
80
Sexual differentiation begins between 6th and 7th weeks of gestation. What activates the events that leads to to the differentiation of the gonad to testes?
SRY gene; 6-12 weeks is the critical time for external virilzation of the male fetus
81
When do you use PTU for maternal hyperthyroidism
1st trimester, then methimazole in the 2nd and 3rd
82
What are the possible fetal effects from exposure to methimazole
cutis aplasia congenita, choanal atresia, TEF, esophageal atresia
83
What is the most useful for the management of hypocalcemia?
calcitriol (aka Vit D)
84
normal osteoid production and decreased bone mineralization is consistent with?
osteomalacia; because osteoblast are still able to make matrix, the mineral content of bone is decreased and the bones are softer and more radiolucent
85
This diagnosis is characterized by decreased bone matrix as a result of either decreased deposition or increased matrix resorption
osteopenia of prematurity
86
What hormones positively influences mineral accretion in the fetus
maternal estrogen; it has an anabolic effect on bone growth and positively influences mineral accretion
87
What is elevated in the preterm infant compared to the term infant with regard the thyroid hormones and protiens?
serum Thyroglobulin is higher in preterm infants compared to term infants. But preterm infants have lower T3, T4, lower iodide stores and decreased TBG levels compared to term infants
88
What is the first hormone to stimulate Wolffian duct differentiation?
testosterone
89
What is the primary action of PTH in the intestin?
increased renal production of active form of Vit D and thus indirectly increases Ca and P intestinal reabsoprtion
90
What effect do low phosphate formulas have on calcium?
help maxmize calcium re-absorption
91
Which hormons if responsible for phallic development prior to the 8th week of gestation?
hCG
92
A term infant is born to parents that had a free cell DNA showing an XY genotype. BW 3400 g and length 50 cm. The infant has a micropenis and a urethral meatus at the base. The infant's testes are palpable in the inguinal canal bilaterally. The FOB has a mutation in the DNA binding of the androgen receptor. What lab test will be abnormally high in this infant?
Dihydrotestosterone drives the virilzation process in both males and females. A mutation in the androgen receptor (encoded on x chromosome), can lead to disorders of sexual development. Lack of androgen signaling leads to decreased virilization. In patients with androgen receptor (AR) mutation, testosterone is upregulated due to lack of GnRH inhibition by testosterone. Patients with AR mutations do not have adrenal defects so cortisol and electrolyte abnormalities are not expected.
93
What are the initial lab studies needed in a patient with ambiguous genitalia?
electrolytes to monitor for salt wasting due to CAH, karyotype, FISH for SRY, and pelvic US. At > 48 hrs of life, serum for 17 OH Progesterone, FSH, LH, testoserone and estradiol. Consult Endocrine
94
What structures form from the Mullerian duct?
uterus, fallopian tubes, upper 2/3 of the vagina
95
Which hormone is primarily responsible for the development of the normal male external genitalia?
Dihydrotesterosterone (DHT). It is needed for fusion of the urethral and labioscrotal fold, lengthening of the genital tubercle and regression of the urogenital sinus
