Endocrinology_1 Flashcards
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)
α subunit is the hormone subunit common to which hormones?
TSH• LH• FSH• hCG
function of the β 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?
α, β, δ endocrine cells
Islets of Langerhans arise from what?
pancreatic buds
what is the position and major product of the α cells of the pancreas?
glucagon (peripheral)
what is the position and major product of the β cells of the pancreas?
insulin (central)• INSulin INSide
what is the position and major product of the δ 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 β 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?
β islet cells• liver• kidney• small intestine
what is the distribution of GLUT-4?
adipose tissue, skeletal muscle
what are the anabolic effects of insulin?
- increase glucose transport in skeletal muscle and adipose• 2. increase glycogen synthesis and storage• 3. increase triglyceride synthesis and storage• 4. increase Sodium retention in the kidney• 5. increase protein synthesis in the muscles• 6. increase cellular uptake of K+ and amino acids• 7. decrease glucagon release
which regulators lead to an increase in insulin?
hyperglycemia• GH• β2 antagonists
which regulators lead to a decrease in insulin?
hypoglycemia• somatostatin• α2- 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 α 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, β-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 3β-hydroxy steroid dehydrogenase?
- converts pregnenolone to progesterone• 2. converts 17-hydroxypregnenolone into 17-hydroxyprogesterone• 3. converts dihydroepiandosterone (DHEA) into androstenedione
what is the function of 17α-hydroxylase?
converts pregnenolone to 17-hydroxypregnenolone and converts progesterone into 17-hydroxyprogesterone
what is the function of 21-hydroxylase?
- converts progesterone into 11-deoxycorticosterone• 2. converts 17-hydroxyprogesterone into 11-deoxycortisol
what is the function of 11β-hydroxylase?
- 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?
- converts androstenedione to estrone• 2. converts testosterone to estradiol
what is the function of 5α-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 17α-hydroxylase deficiency?
high mineralocorticoids• low cortisol• low sex hormones
how does 17α-hydroxylase deficiency present in both sexes?
hypertension, hypokalemia
what are the presenting features of 17α-hydroxylase deficiency that are unique to males?
low DHT–> pseudohermaphroditism (variable, ambiguous genitalia; undescended testes)
what are the presenting features of 17α-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
what are the hormone levels seen in 21-hydroxylase deficiency?
low mineralocorticoids• low cortisol• high sex hormones
how does 21-hydroxylase deficiency present?
hypotension, hyperkalemia, increase renin activity, volume depletion• - masculinization, leading to pseudohermaphrodtism in females
what are the hormone levels seen in 11β-hydroxylase deficiency?
low aldosterone• high 11-deoxycorticosterone• low cortisol• high sex hormones
how does 11β-hydroxylase deficiency present?
hypertension (11-deoxycorticosterone is a mineralocorticoid and secreted in excess)• masculinization
what is the source of cortisol?
adrenal zona fasciculata
cortisol is bound to what in the blood?
corticosteroid-binding globulin
what are the functions of cortisol?
- maintains blood pressure• 2. decreases bone formation• 3. anti-inflammatory/immunosuppressive• 4. increases insulin resistance• 5. increases gluconeogenesis, lipolysis, proteolysis• 6. inhibits fibroblasts
how does cortisol act to maintain blood pressure?
upregulates α1 receptors on arterioles –> increased sensitivity to NE and Epi
what are the anti-inflammatory/immunosuppressive functions of cortisol?
- inhibits production of leukotrienes and prostaglandins• 2. inhibits leukocyte adhesion–> neutrophilia• 3. blocks histamine release from mast cells• 4. reduces eosinophils• 5. blocks IL-2 production
what is the effect of chronic stress on cortisol levels?
chronic stress induces prolonged secretion
what is the effect of CRH on cortisol?
CRH (hypothalamus) stimulates ACTH release (pituitary), causing cortisol production in adrenal zona fasciculata.
what is the effect of excess cortisol on the hypothalamic pituitary axis?
leads to decreased CRH, ACTH, and cortisol secretion
what is the source of PTH?
Chief cells of the parathyroid
what is the effect of PTH on serum Ca2+, PO4, and urine PO4?
increase serum Ca++• decrease serum PO4• increase urine PO4
what are the functions of PTH?
- increase bone resorption of calcium and PO4• 2. increase kidney resorption of calcium in DCT• 3. decrease resorption of PO4 in PCT• 4. increase 1,25-OH2VitD production by stimulating kidney 1α-hydroxylase• 5. increase production of M-CSF and RANK-L in osteoblasts, stimulating osteoclasts
what is the effect of decreased serum calcium on PTH?
increase PTH secretion
what is the effect of decreased serum magnesium on PTH secretion?
increase PTH secretion
what is the effect of a dramatic decrease in serum magnesium on PTH?
decrease PTH secretion
what are the common causes of decreased Mg2+?
diarrhea• aminoglycosides• diuretics• alcohol abuse
what is the source of Vitamin D?
- D3 from sun exposure in skin• 2. D2 ingested from plants• - Both converted to 25-OH in liver and to 1,25-(OH)2 (active form) in kidney.
what is 24,25-(OH)2D3?
an inactive form of vitamin D
Vitamin D deficiency causes what?
rickets in kids and osteomalacia in adults
what is the function of vitamin D?
- increase absorption of dietary Ca and PO4• 2. increase bone resorption of Ca and PO4
which regulators cause an increase in 1,25-OH2 Vit D production?
- high PTH• 2. low [Ca++]• 3. low PO4
what regulators cause a decrease in 1,25-OH2 Vit D production?
1,25-OH2 Vit D feedback
what is the difference between PTH and Vitamin D?
PTH leads to increase Ca++ reabsorption and decrease PO4 reabsorption in the kidney, whereas 1,25-OH2 Vit D leads to increased absorption of both Ca++ and PO4 in the gut.
what is the source of calcitonin?
parafollicular cells (C cells) of the thyroid
what is the function of calcitonin?
decrease bone resorption of calcium• opposes actions of PTH• not important in normal calcium homeostasis.
how is calcitonin regulated?
high serum calcium causes calcitonin secretion
which endocrine hormones act via the cAMP signaling mechanism?
FSH, LH, ACTH, TSH, CRH, hCG, ADH (V2 receptor), MSH, PTH, calcitonin, GHRH, glucagon• - FLAT ChAMP
which hormones act via the cGMP signaling mechanism?
ANP• NO (EDRF)• think vasodilators
which hormones act via the IP3 signaling mechanism?
GnRH, GHRH, Oxytocin, ADH (V1 receptor), TRH, histamine (H1), ATII, gastrin• GGOAT
which hormones act via the steroid receptor mechanism?
Vitamin D, Estrogen, Testosterone, T3/T4, Cortisol, Aldosterone, Progesterone• VETTT CAP
which hormones act via the intrinsic tyrosine kinase signaling mechanism?
insulin• IGF-1• FGF• PDGF• EGF• MAP kinase pathway• Think growth factors
which hormones act via the Receptor-associated tyrosine kinase signaling mechanism?
Prolactin, Immunomodulators (cytokines, IL2, IL6, IL8, IFN), GH• JAK/STAT pathway• Think acidophiles and cytokines
what is the effect of high sex hormone-binding globulin in men?
lowers free testosterone–> gynecomastia
what is the effect of low SHBG in women?
raises free testosterone–> hirsutism
when do SHBG levels increase in women?
during pregnancy
what are T3/T4?
iodine- containing hormones that control the body’s metabolic rate
what is the source of T3/T4?
follicles of thyroid. most T3 formed in target tissues