Endocrine Flashcards – First Aid for the USMLE STEP 1

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  • Thyroid diverticulum arises from what?
    floor of primitive pharynx--> descends into neck
  • thyroid connected to tongue by what?
    "thyroglossal duct, which normally disappears but may persist as pyramidal lobe of the thyroid"
  • foramen cecum is what?
    normal remnant of thyroglossal duct
  • most common ectopic thyroid tissue site is where?
    tongue
  • thyroglossal duct cyst presents as what?
    an anterior midline neck mass that moves with swallowing
  • thyroglossal duct cyst must be dDx from what?
    persistent cervical sinus leading to branchial cleft cyst in lateral neck
  • fetal adrenal gland consists of what?
    an outer adult zone and an inner active fetal zone
  • features of adult zone of fetal adrenal gland?
    "dormant during early fetal life, but begins to secrete cortisol late in gestation"
  • control of cortisol secretion in fetus?
    controlled by ACTH and CRH from fetal pituitary and placenta.
  • role of cortisol in fetal development?
    cortisol is responsible for fetal lung maturation and surfactant production
  • adrenal cortex is derived from which germ layer?
    mesoderm
  • adrenal medulla is derived from which germ layer?
    neural crest
  • layers of adrenal gland from outer to inner?
    Capsule --> Zona Glomerulosa--> Zona Fasciculata --> Zona Reticularis--> Medulla- Chromaffin cells
  • "in adrenal gland, GFR corresponds with what?"
    "Salt (Na+), Sugar (glucocorticoids), Sex (androgens) The deeper you go the sweeter it gets"
  • secretory product of Zona Glomerulosa of adrenal gland?
    Aldosterone
  • secretory product of Zona Fasciculata of adrenal gland?
    "cortisol, sex hormones"
  • secretory product of the zona reticularis of the adrenal gland?
    Sex hormones (androgens)
  • secretory products of chromaffin cells?
    catecholamines
  • Primary regulatory control of the Zona Glomerulosa?
    Renin-Angiotensin
  • primary regulatory control of the Zona Fasciculata?
    ACTH hypothalamic CRH
  • primary regulatory control of the Zona Reticularis?
    "ACTH, hypothalamic CRH"
  • primary regulatory control of adrenal medulla?
    preganglionic sympathetic fibers
  • most common tumor of the adrenal medulla in adults?
    pheochromocytoma
  • most common tumor of the adrenal medulla in children?
    neuroblastoma
  • difference in the presentation between pheochromocytoma and neuroblastoma?
    pheochromocytoma causes episodic hypertension and neuroblastoma does not
  • what is the venous drainage of the left adrenal gland?
    left adrenal --> left adrenal vein --> left renal vein --> IVC
  • what is the drainage of the right adrenal gland?
    right adrenal --> right adrenal vein --> IVC
  • function of the posterior pituitary (neurohypophysis)?
    "Secretes ADH and oxytocin, made in the hypothalamus and shipped to the posterior pituitary via neurophysins (carrier proteins)."
  • posterior pituitary is derived from which germ layer?
    neuroectoderm
  • function of the anterior pituitary?
    "Secretes FSH, LH, ACTH, TSH, prolactin, GH, melanotropin (MSH)"
  • anterior pituitary is derived from which germ layer?
    derived from oral ectoderm (rathke's pouch)
  • alpha subunit is the hormone subunit common to which hormones?
    TSH LH FSH hCG
  • function of the beta subunit of anterior pituitary hormones?
    determines hormone specificity
  • acidophils of the anterior pituitary secrete what?
    GH prolactin
  • how do you remember the hormones secreted by basophils of the anterior pituitary?
    "B-FLAT Basophils- FSH, LH, ACTH, TSH"
  • how do you remember the hormones secreted by the anterior pituitary?
    "FLAT PiG: FSH, LH, ACTH, TSH, Prolactin, GH"
  • Islets of Langerhans are collections of what types of cells?
    "alpha, beta, delta endocrine cells"
  • Islets of Langerhans arise from what?
    pancreatic buds
  • what is the position and major product of the alpha cells of the pancreas?
    glucagon (peripheral)
  • what is the position and major product of the beta cells of the pancreas?
    insulin (central) INSulin INSide
  • what is the position and major product of the delta cells of the islets of Langerhans?
    somatostatin (interspersed)
  • what is the major regulator of insulin release?
    glucose
  • how is insulin released?
    ATP generated by glucose metabolism closes K+ channels and depolarizes beta cell membrane --> opens voltage gated Ca++ channels. Ca++ influx stimulates insulin secretion
  • does insulin cross the placenta?
    no
  • what are the tissues that have insulin-dependent glucose uptake?
    "Brain, RBC's, Intestine, Cornea, Kidney, Liver BRICK L"
  • what are the insulin dependent glucose transporters?
    GLUT-4
  • what is the bidirectional glucose transporter?
    GLUT2
  • what is the distribution of GLUT-1?
    RBC's Brain
  • what is the distribution of GLUT-2?
    beta islet cells liver kidney small intestine
  • what is the distribution of GLUT-4?
    "adipose tissue, skeletal muscle"
  • what are the anabolic effects of insulin?
    1. increase glucose transport in skeletal muscle and adipose 2. increase glycogen synthesis and storage 3. increase triglyceride synthesis and storage (refer to book for more info)
  • which regulators lead to an increase in insulin?
    hyperglycemia GH beta2 antagonists
  • which regulators lead to a decrease in insulin?
    hypoglycemia somatostatin alpha2- agonists
  • which is the insulin independent transporter?
    GLUT-1
  • which tissues depend on insulin for increased glucose uptake?
    resting skeletal muscle and adipose tissue (GLUT-4)
  • which tissues take up glucose independent of insulin levels?
    Brain and RBC (GLUT-1)
  • Brain depends on what substances for energy?
    depends on glucose for metabolism under normal circumstances and uses ketone bodies in starvation
  • RBC's depend on what substance for energy?
    RBC's always depend on glucose because they have no mitochondria for aerobic metabolism
  • what is the source of glucagon?
    made by alpha cells of the pancreas
  • what are the catabolic effects of glucagon?
    glycogenolysis gluconeogenesis lipolysis ketone production
  • how is glucagon regulated?
    "secreted in response to hypoglycemia inhibited by insulin, hyperglycemia, and somatostatin"
  • what stimulates the release of TSH and prolactin?
    TRH
  • what inhibits the release of prolactin?
    dopamine
  • what is the function of CRH?
    "stimulates the release of ACTH, MSH, beta-endorphin"
  • what is the function of GHRH?
    stimulate the release of GH
  • what inhibits the release of GH and TSH?
    somatostatin
  • what is the function of GnRH?
    stimulate the release of FSH and LH
  • what inhibits the release of GnRH?
    prolactin
  • what is the source of prolactin?
    secreted mainly by anterior pituitary
  • what is the function of prolactin?
    stimulates milk production in breast; inhibits ovulation in females and spermatogenesis in males by inhibiting GnRH synthesis and release
  • prolactin secretion from anterior pituitary is tonically inhibited by what?
    dopamine from hypothalamus
  • how does prolactin inhibit its own secretion?
    by increasing dopamine synthesis and secretion from hypothalamus
  • what hormone increases prolactin secretion?
    TRH
  • what inhibits prolactin secretion and can be used in treatment of prolactinoma?
    dopamine agonists (bromocriptine)
  • which drugs stimulate prolactin secretion?
    "dopamine antagonists (most antipsychotics) estrogens (OCP's, pregnancy)"
  • what is the source of growth hormone?
    secreted mainly by anterior pituitary
  • what is the function of growth hormone?
    stimulates linear growth and muscle mass through IGF-1/somatomedin secretion
  • what is the effect of GH on blood sugar?
    increases insulin resistance (diabetogenic)
  • GH is released in pulses in response to what?
    GHRH
  • when does GH secretion increase?
    during exercise and sleep
  • secretion of GH is inhibited by what?
    glucose and somatostatin
  • what can cause excess secretion of GH?
    pituitary adenoma
  • excess secretion of GH can cause what?
    acromegaly in adults or gigantism in children
  • which hormone activates cholesterol desmolase?
    ACTH
  • which drug inhibits cholesterol desmolase?
    ketoconazole
  • what is the function of desmolase?
    converts cholesterol into pregnenolone
  • what is the function of 3beta-hydroxy steroid dehydrogenase?
    1. converts pregnenolone to progesterone 2. converts 17-hydroxypregnenolone into 17-hydroxyprogesterone 3. converts dihydroepiandosterone (DHEA) into androstenedione
  • what is the function of 17alpha-hydroxylase?
    converts pregnenolone to 17-hydroxypregnenolone and converts progesterone into 17-hydroxyprogesterone
  • what is the function of 21-hydroxylase?
    1. converts progesterone into 11-deoxycorticosterone 2. converts 17-hydroxyprogesterone into 11-deoxycortisol
  • what is the function of 11beta-hydroxylase?
    1. converts 11-deoxycorticosterone into corticosterone 2. converts 11-deoxycortisol into cortisol
  • what is the function of aldosterone synthase?
    converts corticosterone into aldosterone
  • what hormone activates aldosterone synthase?
    angiotensin II
  • what is the function of aromatase?
    1. converts androstenedione to estrone 2. converts testosterone to estradiol
  • what is the function of 5alpha-reductase?
    converts testosterone into DHT
  • all congenital adrenal enzyme deficiencies are characterized by what?
    enlargement of both adrenal glands due to high ACTH stimulation because of low cortisol
  • what are the hormone levels seen in 17alpha-hydroxylase deficiency?
    high mineralocorticoids low cortisol low sex hormones
  • how does 17alpha-hydroxylase deficiency present in both sexes?
    "hypertension, hypokalemia"
  • what are the presenting features of 17alpha-hydroxylase deficiency that are unique to males?
    "low DHT--> pseudohermaphroditism (variable, ambiguous genitalia; undescended testes)"
  • what are the presenting features of 17alpha-hydroxylase deficiency unique to females?
    "external phenotypic female with normal internal sex organs, lacks 2ndary sex characteristics"
  • what is the most common form of congenital bilateral adrenal hyperplasia?
    21-hydroxylase deficiency
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