Endocrine physiology Flashcards
What are examples of hormones which are produced by anterior pituitary basophils?
Be FLAT
- FSH
- LH
- ACTH
- TSH
What colour are the basophils?
Deep blue/purple
What are examples the hormones secreted by acidophils?
Acid PiG
- Prolactin
- GH
What colour are the acidophils?
Pink
What is the alpha subunit common to?
- TSH
- LH
- FSH
- hCG
Describe generally how the adrenal gland looks on histology?
Cortex is generally purple and the medulla is blue
- Zona glomerulosa (thin)
- Zona fasiculata (paler and thicker)
- Zona reticularis (thin)
- Adrenal medulla (blue)
What is the primary hormone produced by the zona reticularis?
DHEA
What are the carrier proteins called that transport ADH and oxytocin from hypothalamus to anterior pituitary?
Neurophysins
WHat is the precursor molecule that ACTH and MSH share?
Proopiomelanocortin
How can Cushing’s cause hyperpigentation?
Through proopriomelanocortin which is the precursor molecule to both MSH and ACTH
What is ADH release primarily triggered by?
Decreased plasma osmolarity
What does CRH release?
- ACTH
- MSH
- B-endorphin
What is the GHRH analog which can be used to treat HIV-associated lipodystrophy?
Tesamorelin
What hormones can dopamine suppress?
- Prolactin
- TSH
What ant pituitary hormones does somatostatin suppress?
- GH
- TSH
How does natural contraception during breastfeeding happen?
Causes production of prolactin
- Prolactin then suppresses the release of:
- GnRH (thus LH and FSH)
What does primary prolactinoma cause?
- Galactorrhea
- Hypogonadism
- Amenorrhea
- Osteoperosis
What can GH also be called?
Somatotropin
What is an example of a somatostatin analog which can be used to treat acromegaly?
Octreotide
What does ADH cause when they act on V1 receptors?
Increase BP
What does ADH cause when they act on V2 receptors?
Decreased serum osmolarity (increase urine)
What cells does ADH act on in the renal collecting ducts?
Principle cells of the collecting duct (causes increase in Aquaporin insertion)
What is Leuprolide?
GnRH agonist
TRH causes the release of TSH and can trigger the secretion of what other hormone?
Prolactin
Via what pathway does dopamine inhibit prolacin secretion?
Tuberoinfundibular pathway of hypothalamus
What is an example of a dopamine agonist which can be used in the treatment of prolactinoma?
Bromocriptine
What are examples of dopamine antagonists which can cause prolactin secretion?
- Antipsychotics
- Metoclopramide
- Estrogen
What are the 3 forms plasma Ca2+ may exist?
- Ionised free ~ 45%
- Albumin ~ 40%
- Anions ~ 15%
How does Mg2+ affect PTH levels?
A decrease in Mg2+ causes increased PTH and a large decrease causes a decrease in PTH
How does pH affect calcium and PTH levels?
Increased pH promotes increased protein binding, which decreases free calcium levels and therefore increase PTH levels
What is synthesised in the rough endoplasmic reticulum of the Beta cells?
Preproinsulin
What forms is insulin stored in before being exocytosed?
- Preproinsulin is synthesised in the RER of the B cells
- Cleaved to produce proinsulin
- Proinsulin is stored in secretory granules
- Proinsulin is exocytosed into insulin and C-peptide
What structure is in natural insulin but not in synthetic?
C-peptide
What bonds are present in insulin?
2 disulfide bonds
Where can GLUT1 transporters be found?
- RBCs
- Brain
- Cornea
- Placenta
Where can GLUT2 transporters (bidirectional) be found?
- Beta islet cells
- Kidneys
- Liver
- GI tract
Where can GLUT3 transporters be found?
- Brain
- Placenta
Where can GLUT5 (fructose) transporters be found?
- Spermatocytes
- GI tract
Where can SGLT1/2 transporters be found?
- Kidney
- Small intestine
Where can insulin independant glucose uptake occur?
BRICK LIPS
- Brain
- RBCs
- Intestine
- Cornea
- Kidneys
- Liver
- Islet B cells
- Placenta
- Spermatocytes
Where is the satiety centre located that leptin acts on?
Ventromedial area of hypothalamus
Why is there a bigger insulin response with oral glucose compared with IV?
Incretins:
- glucagon-like peptide (GLP-1)
- Glucose-dependent insulinotropic polypeptide (GIP)
These are released after meals and increase Beta cell sensitivity to glucose
Where are the Beta cells located in the islets?
Centrally
How does Insulin release happen in the Beta cells?
- Glucose enters the cell via GLUT2
- Glycolysis causes increased ATP/ADP ratio
- ATP closes ATP sensitice K+ channel
- Depolarisation occurs voltage-gated Ca2+ channels open
- Increased intracellular Ca2+
- Insulin exocytosed from the granules
How does epinephrine effect insulin release?
Insulin release inhibited and plasma glucose increased
What receptors does insulin act on in the pancreas?
- B2 receptors (which increase insulin release)
- a2 receptors (decrease insulin release)
- Alpha effect is dominant effect in pancreas therefore plasma glucose increased
What enzyme is induced by insulin?
Glucokinase (it converts glucose into G6P)
Why is a bidirection glucose transporter (GLUT2) needed in kidney or liver cells?
Gluconeogenesis
What is the insulin receptor made out of?
- 2 a units (extracellular)
- 2 B units (transmembrane)
Connected by disulfide bonds
What enzyme does insulin activate by activating the insulin receptor?
Tyrosine kinase
What can the brain not use for energy?
fatty acids
- Uses glucose/ketones
Why do RBCs use GLUT1 for glucose uptake?
They lack mitochondria therefore depend on glycolysis
What is lipase inhibited by?
Insulin
Describe how insulin causes glucose uptake into cells?
- Phosphorylates tyrosine on the tyrosine kinase (insulin) receptor
- Recetpror binds substrates (insulin recepetor substrates) (IRS-1,2) these mediate downstream effects
- PIK3 pathway and RAS/MAP kinase pathway
- Phosphatidylinositol 3-kinase pathway forms PIP3 from PIP2
- Glycogen, lipid synthesis + GLUT4 releaase from vesicles
- RAS/MAP kinase pathway causes cell growth and DNA synthesis
What pathway is responsible for the uptake of GLUT4 and glycogen, lipid and protein synthesis?
Phospoinositide-3 kinase pathway
What tissues are insulin dependent?
Muscle and fat
How does insulin affect glycogen and glucose levels?
- Glycogen synthesis (activates glycogen synthase and inhibits glycogen phosphorylase)
- Inhibits gluconeogenesis (increases fructose-2,6-biphosphate levels and inhibits frictose 1,6 biphosphate 1)
How does cortisol regualte itself?
Excess cortisol decreases CRH and ACTH and cortisol secretion
What are the functions of cortisol?
A BIG FIB
- Increases apetite
- Increases BP (upregulates a1 receptors) and can bind to aldosterone receptors
- Increases insulin resistance (diabetogenic)
- Increases gluconeogenesis, lipolysis and proteolysis (decreased glucose utilisation)
- Decreased Fibroblast activity
- Decrease Inflammatory and immune responses (inhibits leukotrienes and prostaglandins, WBC adhesion, neutrophilia. Blocks histamine release from mast cells, eosinophilia, lymphopenia. Blocks IL-2 production
- Decreases bone formation thru decreasing osteoblast activity
What processes does glucagon promote?
- Glycogenolysis
- Gluconeogenesis
- Lipolysis
- Ketogenesis
What is glucagon inhibited by?
- insulin
- Amylin
- Somatostatin
- Hyperglycemia
What genetic disorder causes increased ghrelin production?
Prader-Willi syndrome (deletion of chr15 from father)
Where does ghrelin act on?
Lateral area of hypothalamus (hunger centre)
Do obese people have increased leptin?
Yes (incr adipose) but they are resistant/tolerant to its anorexigenic effect
How does sleep deprivation effect leptin?
Decreases leptin (more hungry/less satiated)
What do endocannabinoids act on?
Cannabinoid receptors in hypothalamus and nucleus accumbens, 2 key brain areas for the homeostatic and hedonic control of food intake - increases apetite
