endocrinology

Question 1

Thyroid development

Answer 1

Thyroid diverticulum arises from floor of primitive pharynx and descends into neck

Connected to tongue by thyroglossal duct, may perisist as cysts or the pyrimidal lobe of thyroid

ectopic thyroid tissue site is the tongue, removal may result in hypothyroidism if it is the only thyroid tissue present

Thyroglossal duct cyst presents as an anterior midline neck mass that moves with swallowing or protrussion of the tongue , thyroid follicular cells derived from endoderm

Question 2

anterior pituitary

Answer 2

Anterior pituitary (adenohypophysis)

Secretes FSH, LH, ACTH, TSH, prolactin, GH, and B endorphin

Melantropin (MSH) secreted from intermediate lobe

Question 3

Posterior pituitary…neurohypophysis

Answer 3

Stores and releases vasopressin (ADH) and oxytocin

both are made in the hypothalamus (supraoptic and paraventricular nuclei) and transported to posterior via neurohphysins (carrier proteins)

Derived from neuroectoderm

Question 4

Adrenal cortex

Answer 4

GFR- G (ANG2 - mineralocorticoids, Aldosterone) ACTHCRH ( Glucocorticoids and Androgens

Medulla - chromaffin cells ( make catecholamines, epi NE)

Question 5

ADH

Answer 5

increases water permeaability of distal convoluted tubule and collecting duct cells in the kidney to increase water reabsorption

increased plasma osmolality increases release, in SIADH ADH goes up even though plasma osmolality is decreased

Question 6

CRH

Answer 6

increased ACTH MSH B-endorphins

decreased in chronic exogenous steroid use

Question 7

Dopamine

Answer 7

decreases prolactin secretion
Makes TSH

prolactin-inhibiting factor
Dopamine antagonists (antipsychotics) can cause galatorrhea due to hyperprolactinemia

Question 8

GHRH and hrowth hormone

Answer 8

increases GH secretion

Analog is tesamorelin used to treat HIV associated lipodystrophy

Also called somatotropin, secreted by anterior pituitary

Stimulates linear growth and muscle mass through IGF1 (Somatomedin C) secretion by liver)) increases insluin resistence (you want resistence when growing

Released in pulses in response to GHRH, Secretion increases during exercise, deep sleep, puberty, hypoglycemia, CKD

Secretion decreased by glucose, Somatostatin, somatomedin (IGF1)

Excess secretion of GH (pituitary adenoma) may cause acromegaly or gigantism, treatment- somatostatin analogs (octreotide) or surgery

Question 9

GnRH

Answer 9

increases FSH and LH release

Suppressed by hyperprolactinemia

Tonic GnRH analog (leuprolide) suppresses hypothalamic-pituitary gonadal axis

Pulsatile GnRH leads to puberty and fertility

Question 10

MSH

Answer 10

increases melanogenesis by melanocytes

hyperpigmentation in Cushing disease, as MSH and ACTH share the same precursor molecule proopiomelanocortin

Question 11

Oxytocin

Answer 11

Causes uterine contractions during labor

Responsible for milk let down reflext during sucking

Modulates fear, anxiety, social bonding, mood and depression

Question 12

Prolactin

Answer 12

decreases GnRH
stimulates lactogenesis

pituitary prolactinoma–> amenorrhea, osteoporosis, hypogonadism, galactorrhea

Breastfeeding–> increased Prolactin–> decreased GNRH –> delayed postpartum ovulation

Question 13

Somatostatin

Answer 13

decreases GH, TSH

GHinhibitinghormonee
Analogs used to treat acromegaly

Question 14

TRH

Answer 14

increases TSH prolactin

Increased TRH (hyporthyroididsm

Question 15

ADH vasopressin

Answer 15

synthesized in hypothalamus (supraoptic and paraventricular nuclei) stored and secreted by posterior pituitary

Regulates b1ood pressure (V1 receptors) and serum osmolality (V2 receptors)
Regulation of renal collecting duct aquaporins

ADH level is decreased in central DI, normal/increased in nephrogenic

Nephrogenic DI can be caused by mutation in V2 receptor

Desmopressin is the treatment for central DI and nocturnal enuresis (its an ADH analog)

Regulated by plasma osmolality, hypovolemia (ADH goes up)

Question 16

Prolactin

Answer 16

Secreted mainly by Anterior pituitary
Stimulates milk production in breast

structually looks like growth hormone

Inhibits GnRH (affecting fertility)

inhibited by dopamine from tuberinfundibular tract of hypothalamus

Bromocriptine inhibits prolactin by stimulating prolactin secretion via being a dopamine agonist

Question 17

Thyroid hormones

Answer 17

Thyroid produces T3 and T4, iodine containing hormones that control the body’s metabolic rate

Source: follicles of thyroid, 5’ deiodinase converts T4 (the major thyroid product) to T3 in peripheral tissue
(5,4,3)
Peripheral conversion is inhibited by glucocorticoids, B-blockers, propylthiouracil (PTU)
Reverse T3 (rT3) is a metabolically inactive byproduct of the peripheral conversion of T4 and its production is increased by growth hormone and glucocorticoids

T3 is increased by growth hormne and glucocorticoids

Functions of thyroid peroxidase include oxidation, orgarnification of iodine, and couplining of MIT and DIT. Inhibites by PTU and methimazole

Wolff-Chaikoff effect- excess iodine temporarilly turns off thyroid peroxidase (decreased T3, T4 production

Function of T3 (free, T3 binds nuclear receptor better than T4) 7Bs- brain maturation, Bone growth (synergism with GH), B-adrenergics, Basal metabolic rate increase, Blood sugar increases, Break down lipids (hyper lipidemia), stimulates surfactant synthesis in babies)

Question 18

Parathyroid hormone

Answer 18

chief cells of parathyroid

Free Ca++ in blood, increased Ca and PO4 absorption in GI system, increased Ca and PO4 resorption
Increased CA reab from DCT

decreased PO4 reabsorption PCT

Increases 1a-hydroxylase in PCT (increased 1,25 OH2D (calcitriol D3)

PTH increases RANKL (receptor NF kB Ligand secreted by osteoblasts and osteocytes binds RANK r on osteoclasts–> increase Ca release

Decreased serum calcium, increased serum PO4, decreased serum Mg all INCREASE PTH

Very decreased MG will decrease PTH secretion

Question 19

Ca homeostasis

Answer 19

Plasma Ca exists in 3 forms

ionized /free (45% in active form)
bound to albumin 40%
Bound to anions 15%

increased pH (less H+, less anealing) –> albumin binds more Ca–> decreased ionized Ca (cramps pain parasthesias, carpopedal spasm –>increased PTH

decreased pH (messes up albumin)–> binds less Ca - increased ionized CA–> decreased PTH

free Ca is the 1’ regulator of PTH changes in ph alter pth secretion, whereas changes in albumin dont

Question 20

Calcitonin

Answer 20

Parafollicular cells (C cells of thyroid

decrease bone resorption of Ca
increase serum Ca –> increased Calcitonin secretion

Calcitonin opposes actions of PTH

Question 21

Glucagon

Answer 21

Made by a cells of pancreas

Promotes glycogenolysis, gluconeogenesis, lipolyis, ketogenesis

Elevates blood sugar levers to maintain homeostasis when blood stream glucose levels fall too low

Secreted in response to hypoglycemia, inhibited by insulin, hyperglycemia, somatostatin

Question 22

insulin

Answer 22

Preproinsulin (synthesized in RER of pancreatic B cells)–> cleavage of presignal –> proinsulin (stored in secretoryt granules–> cleavage of proinsulin–> exocytosis of insulin and C peptide

binds insulin tyrosine kinase–> induces glucose uptake (carrier-mediated transport) into insulin dependent tissue and gene transcription

increased glucose transport skeletal muscle and adipose tissue, glycogen synthesis and storage, TG synthesis, Na retention kidneys), protein synthesis (muscles), cell uptake of K and amino acids, decreases glucagon release, decreases lipolysis in adipose tissue

Insulin doesnt cross placenta (glucose does)

Glut 4 is insulin dependent (adipose tissue, striated muscle (excercise cn also increase GLUT 4)

Glut 1 (RBCs, brain, cornea, placenta)
Glut 2 (bidirectional B islet cells, liver, kidney, GIT (2 ways
Glut 3- brain and placenta
Glut 5- fructose in spermatocytes, GIT

Question 23

Regulation of insulin

Answer 23

Glucose is major regulator of insulin release. increased insulin response

increased insulin response with oral vs IV glucose due to incretins (GLP1) and GIP

Glucose enters B cells–> increase ATP generated from glucose metabolism–> closes K channels –> depolarization of B cells –> Voltage gatesd Ca chennels open–> Ca influx–> stimulates insulin exocytosis

Question 24

17 a hydroxylase deficiency

Answer 24

increased mineralocorticoids–> decreased K and increased BP

decreased cortisol, decreased Sex hormones
decreased androstenedione

XY- ambiguous genitalia, undescended testes
XX- lacks 2’ sexual development

Question 25

21 hydroxylase deficiency

Answer 25

Most common

decreased mineralocorticoids (like taking spironolactone)

increased K, decreased BP, decreased Cortisol, increased sex hormones

increased renin, increased 17 hydroxy progesterone

Presents in infancy (salt wasting) or childhood precocious puberty

XX- virilization

Question 26

11 B hydroxylase

Answer 26

decreased aldosterone, increased 11 deoxycorticosterone (increased BP)

decreased K BUT increased BP

decreased cortisol

increased Sex hormones

decreased renin activity

infants have hypertension, with precocious puberty
XX- virilization

Question 27

Cortisol

Answer 27

increases Appetite, increase Blood pressure (upregulates a receptors on arterioles so increased sensitivity to NE and EPu, at high concentrations can bind to mineralocorticoids receptors, increased gluconeogenesis lipolysis, and proteolysis
decreased fibroblast activity (poor wound healing, decreased collagen synthesis, increased stria

decreased infalmmatory and immune responses (inhibits leukotrienes and PGs, inhibits WBC adhesion–> neutrophilia, blocks histamine release from mast cells, eosinopenia, lymphopenia, Blocks IL2 production

Decreases bone formation

Question 28

Appetite regulation

Answer 28

Grelin- stimulates hunger (orexigenic effect) and GH release (via GH secretagog receptor)

Obese people have increased leptin due to increased adipose tissue, but decreased sensitivty to it

Sleep dep ==> leptin down regulates

Endocannabinoids–> increase appetite