Endocrine Flashcards
Thyroid dysgenesis T4 & TSH
T4 low or normal
TSH high
Organification, thyroglobulin defects and deiodinase deficiency T4 & TSH
T4 low
TSH high
Thyroid hormone resistance T4 & TSH
T4 high
TSH normal or high
TSH deficiency T4 & TSH
T4 low
TSH normal or low
TRH deficiency T4 & TSH
T4 low
TSH low
Transient hypothyroidism T4 & TSH
T4 low or normal
TSH variably high
TBG deficiency T4 & TSH
T4 low
TSH normal
Transient hypothyroxinemia of prematurity T4 & TSH
T4 low
TSH normal or low
Sick euthyroid T4 & TSH
T4 low or normal
TSH normal
Draw adrenal cortex pathway
Google picture for confirmation
Causes of virilized female
Increased androgen production (CAH d/t 21H def, 11B def, 3B def), abn androgen metabolism (aromatase def), increased maternal androgen exposure
Causes of undervirilized male
Decreased testosterone synthesis (CAH d/t 17a def, 3B def; abn leydig cell production of testosterone)
Abn testosterone metabolism (5 alpha reductase deficiency)
Defect of testosterone action (androgen resistance or androgen insensitivity)
What substrates maintain glycogenolysis and gluconeogenesis
Lactate/pyruvate from anaerobic glycolysis
Gluconeogenic amino acids
Glycerol
Propionic acid
Etiologies of neonatal hypoglycemia
Prematurity
Sepsis
Hyperinsulinemia (IDM, SGA or LGA, discordant twins, perinatal depression, BWS, pancreatic islet adenoma)
Hormonal abn (panhypopit, GH def, cortisol def)
IEM (carbohydrate disorders, protein abnormalities, organic acidemias, fatty acids abn)
Carbohydrate disorders that can cause hypoglycemia
Galactosemia
GSD
Hereditary fructose intolerance
Protein abnormalities that can lead to hypoglycemia
Maple syrup urine disease
Organic acidemias that can cause hypoglycemia
Propionic acidemia, methylmalonic acidemia, beta methylcrotonyl glycinuria, glutaric aciduria type I and II
Fatty acid abnormalities that can lead to hypoglycemia
Long chain 3 hydroxyacyl coA deficiency
Calcium and the preterm infant
Accretion occurs during third trimester so they have low stores, abnormal calcium absorption from the intestines, increase losses of Ca and P from kidney, and physiologic hypoparathyroidism
Causes of early hypocalcemia
Birth-72h
Maternal: diabetes (bc leads to dec calcium which leads to less transfer), pet (leads to increased maternal mag and decreased PTH release), hyperparathyroidism
Prematurity, growth restriction, perinatal depression, infection, hypomagnesemia, blood product transfusion
Causes of late neonatal hypocalcemia
> 72h
Hypoparathyroidism (22q11.2, familial AD, AR, x-linked recessive)
Transient neonatal pseudohypoparathyroidism 2/2 blunted phosphaturic response to PTH
Hypomag
But D def, renal insufficiency, high phosphate milk diet, malabsorption, alkalosis, liver or renal disease, drug induced
Assessment of hypocalcemia
Total serum ca, ionized ca, phosphate, creatinine, ALK-P, urine ca excretion, calcitriol, CD4 count, skeletal radiographs, chest XR for thymic shadow
Schizencephaly
Abnormal clefts in the brain
Lissencephaly
Underdevelopment of gyri - smooth brain
Pachygyria
Broad and abnormally large gyri leading to less sulci
Polymicrogyria
Numerous small convolutions
Colpocephaly
congenital abnormality in which the occipital horns of the lateral ventricles are larger than normal because white matter in the posterior cerebrum has failed to develop or thicken
Thyroid hormone function
Basal metabolic rate
Thermogenesis
Stimulates normal growth
Increases bone mineralization and skeletal muscle activity
Increases HR, contractility and cardiac output
CNS maturation
Neonatal hyperthyroidism presenting secondary to maternal graves - timing and length of symptoms
Symptoms typically present by 14 days of age (up to 29 days)
If mom not on anti thyroid meds then present as early as 1-3 days
Symptoms can last 3-6 months
Cortisol production pathway
Hypothalamus secretes corticotropin releasing hormone (CRH)
Anterior pituitary secretes adrenocorticotropic hormone (ACTH)
Adrenal gland produces cortisol which does a feedback loop
Cortisol functions
Induces, gluconeogenesis and antagonizes insulin, leading to increase glucose and lipolysis
Increases calcium and phosphate released from bone
Critical for vascular responses to catecholamines
Decreases inflammation and suppresses immune system
Inhibits a DH, increases gastric acid, secretion, increases production of red blood cells
Important enzymes in adrenal cortex pathway
3 beta hydroxysteroid dehydrogenase
17 alpha hydroxylase
21 hydroxylase
11 beta hydroxylase
17 beta hydroxysteroid dehydrogenase
Aromatase
5 alpha reductase
Laboratory characteristics of 21 OH deficiency
Elevated 17 OH P
Elevated 17 OH P following ACTH administration
Can have salt wasting (75% of cases)
11 beta hydroxylase deficiency lab characteristics
Increased DOC and deoxycortisol
Not salt wasting because DOC acts as mineralcorticoid
17 alpha hydroxylase deficiency lab characteristics
Elevated DOC and corticosterone
Low 17 OH progesterone and 17 OH pregnenolone
Not impacting enzyme of aldosterone pathway
Lab characteristics of 3 beta hydroxysteroid dehydrogenase deficiency
Rare
Elevated 17 OH pregnenolone and DHEA
(All shunted to sex hormone pathway)
Salt wasting
Ambiguous genitalia
Clitromegaly, inguinal mass, labial mass, posterior labial fusion
Micropenis with bilateral cryptorchidism
Hypospadius with undescended testes
Peniscrotal Hypospadius
Ambiguous genitalia workup
Gonads palpable:
US for mullerian structures
17 OHP
karyotype
Infant response to cut of maternal glucose
3-5 fold increase in glucagon
Decrease insulin
Increase catecholamines
All leads to increased gng, glycogenolysis, lipolysis, and ketogenesis
Substrates of gluconeogenesis
Lactate/pyruvate from anaerobic glycolysis
Gluconeogenic amino acids (alanine is very important)
Glycerol
Propionic acid
Etiologies of hypoglycemia
General: prematurity and sepsis
Hyperinsulinism: IDM, SGA, LGA, discordant twin, perinatal depression, BWS, pancreatic islet adenoma
Hormonal abnormalities: panhypopit, GH deficiency, cortisol deficiency
IEM: carbohydrate disorders, protein abnormalities, organic acidemias, fatty acid abnormalities
Review book proposed critical labs for hypoglycemia
Blood gas, BHOB, serum lactate, FFA, insulin level, urine for non glucose reducing substances, urine for ketones
Others: GH and cortisol
Increase in PTH related hormone results in
Increase in calcitriol which leads to maternal increase in calcium absorption from guy and decrease renal calcium excretion
What crosses the placenta with regards to calcium and phosphate metabolism
Calcium, phos and magnesium cross placenta which is greatest in the 3rd trimester
Calcidiol (25OH Vit D) also crosses placenta
Fetus control of calcium
High fetal serum calcium levels leads to increased calcitonin and suppressed fetal PTH
fetal kidney is capable of converting calcidiol to calcitriol (the active form)
Postnatal calcium patterns
Ca level decreases rapidly in first 6 hours with nadir 24-48 hours
PTH increases during 1st day and peaks at 48 HOL
Calcitriol increases and remains constant after 24 HOL
Phosphate is high in first few days and slowly declines
Calcitonin increases after birth and then slowly decreases
Causes of early hypocalcemia
Up to 72 HOL
maternal illness (diabetes bc of less calcium and calcium transfer, preE because of high mag and low pth, hyperpara)
Prematurity, FGR, perinatal depression, infection, hypomag, transfusion, phototherapy?
Causes of late hypocalcemia
After 72 HOL
Hypoparathyroidism, transient neonatal pseudohypoparathyroidisms secondary to blunted phosphaturic response to PTH
Hypomag, Vit d deficiency, renal insufficiency, high phos milk diet, malabsorption
Labs with metabolic bone disease of prematurity
Serum calcium usually normal (but can be increased or decreased)
Serum phos low
Vit 1,25 OH D increased
Alk Phos often increased
Labs of primary hyperparathyroidism
Serum Ca increased
Serum phos decreased
Maybe have hyperchloremic acidosis due to renal effect on PTH
Labs of hypoparathyroidism
Serum ca decreased
Serum phos increased
Pth low
Calcitriol synthesis low
Alkalosis
Paeudohypoparathyroidism labs
serum calcium decreased
Serum phos increased
Tissue resistance to pth
Increased pth
Low calcitriol
Labs of chronic renal failure
Serum ca decreased
Serum phos increased
Pth increased to compensate for low serum ca
Labs of malabsorption
Serum ca decreased
Serum phos decreased
Multiple nutrient deficiency
