Endocrine Flashcards
What are Exocrine Glands?
secrete products into ducts which carry the
secretion into cavities, lumen of an organ and outer surface of the body
e.g. sweat glands
What are Endocrine Glands?
secrete products into interstitial fluid surrounding the secretory cells, this then diffuses into the capillaries and is carried by the blood to the target organ/receptors.
Define Paracrine…
Local hormones which act on neighbouring cells
Define Autocrine…
Hormones which act on the same cell that secreted them e.g. Interleukin-2
Define Haemocrine…
Hormones which travel from the cell which produced them into the blood
Define Solinocrine….
Messenger molecule secreted into hollow lumen of ductal system
Name three water soluble hormones?
Amine hormones
Peptide hormones
Protein hormones
Name three lipid soluble hormones?
Thyroid hormones
Steriod hormones
Nitric oxide
Examples of amine hormones
Catecholamines so adrenaline. nor adrenaline and dopamine
Examples of peptide hormones
ADH, oxytocin, insulin
Examples of protein hormones
Human growth hormone, parathyorid hormone
Examples of thyroid hormones
T3, T4, Calcitonin
Examples of steriod hormones
sex hormones, vitamin D, cortisol
nitric oxide can be
hormone or neurotransmitter
What is the action of lipid soluble hormones?
- Lipid soluble hormone diffuses from the blood to the lipid bilayer of the plasma membrane
- target cell binds to the hormone
- activates receptors located in the nucleus/cytosol
- the receptor hormone complex then alters gene expression and turns certain genes on/off
- new proteins are made and alter cell’s activity
- protein allows response typical of that hormone.
Can water soluble hormones diffuce through the lipid bilayer?
no
What is the action of water soluble hormones?
- Hormones bind to receptor on the membrane
- the hormones act as the first messenger
- the hormone receptor complex activates G-Protein
- G protein activates adenylate cyclase
- Adenylate cyclase converts ATP into cyclic AMP
- Cyclic AMP activates protein kinases
- protein kinase phosphorylates other cellular proteins
- Phosphorylated proteins cause reactions that produce physiological responses.
What does phosphorylates mean?
adds a phosphate group
Which hormones do the thyroid gland produce?
T3, T4 and calcitonin
Which artery supplies the superior thyroid artery?
External carotid artery
Which artery supplies the inferior thyroid artery?
Subclavian artery an dthen th thyrocervical trunk
What is the artery that only around 10% of the population have called?
Thyroid ima artery
Where does the thryoid ima artery come from
brachicephalic trunk of the arch of aorta.
Which cells produce PTH?
Chief Cells
What is the overall role of parathyroid hormone?
increase blood calcium levels
What are the three OTHER functions of parathyroid hormone?
- -Stimulates osteoclastic activity in the bines to mobile bone calcium so increases calcium in the blood
- Stimulates absorption ofdietary calcium from the samll intestine
- Stimulates reabsorption of calcium in the kidney
What controls the parathyroid glands?
The calcium levels in the blood
How are thyroid glands regulated?
- The hypothalmus secretes TRH
- Stimulates TSH in the anterior pituitary
- Then in the thyroid gland, T3, T4 and calcitonin are stimulated
What cells are in thyroid gland?
Follicle cells
Follicle cells are surrounded by….
Blood vessels which contain NA+, I-, K+
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Explain the synthesis of thyroid hormones
-Thyroglobulin is proudced in follicle cells in RER
- I- is cotransported with Na+ into the follicle.
-I- enters the colloid via pendrin channel (chloride iondine channel)
- Iodide then gets oxidised into iodine
-Iodine combines with tyrosine in thyroglobulin to form MIT and DIT
- two T2 molecules join to
form T4, or one T1 and one T2 join to form T3.
-T3 and T4 go into the follicle cells and get broken out of the thyroglobulin by lysosomes.
Role of thyroglobulin
Follicular cells, packages into a vesicle and then secreted via exocytosis into the colloid lumen. They have the amino acid tyrosine attached to them also.
What doe T3 and T4 stand for?
triiodothyronine (T3)
thyroxine (T4)
Which thyroid hormone is needed more
T3 so T4 converts to T3
What is it called when you are T3/T4 deficient?
HypOthyroidism - lOw
Hyperthyroidism - high
Which hormones are produced in the anterior pituitary gland?
Growth hormone Prolactin ACTH-adrenocorticotropin LH FSH TSH MSH-melanocyte stimulating hormone
Which hormonnes are released from the posterior pituitary gland?
ADH/Vasopressin
Oxytcin
Name 5 secreting cells in the hypothalmus ?
- Somatotrophs–GH secreting cells
- Corticotrophs–ACTH secreting cells
- Thyrotroph-TSH secreting cells
- Gonadotroph-LH/FSH secreting cells
- Lactotroph–Prolactin secreting cells
Role of Human Growth Hormone?
- targets tissues in liver
- secreted by Somatotrophs
- Stimulates tissues to synthesise and secrete insulin like (IGFs)
- They promote growth of body cells, protein synthesis, tissue repair, lipolysis and elevation of blood glucose concentration.
Role of Thyroid stimulating hormone?
-targets tissues in thyroid gland
-secreted by thyrotophs
- Stimulates the synthesis and secretion of thyroid
hormones by the thyroid gland.
Role of Follicle stimulating hormone?
- targets the ovaries and testes
- secreted by gonadotophs
- In females, it initiates development of oocytes and induces ovarian secretion of oestrogen.
- In males, stimulates testes to produce sperm.
Role of Luteinising hormone?
-targets the ovaries and testes
-secreted by gonadotrophs
-In females, stimulates secretion of oestrogens and
progesterone, ovulation and formation of corpus luteum.
-In males, stimulates testes to produce testosterone.
Role of Prolactin?
- targets mammary glands
- secreted by Lactotrophs
- Together with other hormones, promotes milk production by mammary glands.
Role of Adrenocorticotropin?
- targets adrenal cortex
- secreted by Corticotrophs
- Stimulates secretion of glucocorticoids (mainly cortisol) by adrenal cortex.
Role of Mealoncyte stimulating hormone?
-targets brain
-secreted by Corticotrophs
-Exact role in humans is unknown but may influence
brain activity; when present in excess it can cause
darkening of the skin
Role of Oxytocin?
-targest uterus and breasts
-secreted by magnocelluar cells
-Stimulates contraction of smooth muscles of
uterus during childbirth.
-Stimulates contraction of myoepithelial cells in
mammary glands to cause milk ejection.
Role of ADH?
- targets kidneys
- secreted by magnocellular cells
- Conserves body water by decreasing urine volume
- decreases water loss through perspiration
- raises blood pressure by constricting arterioles.
Define the main glucose transporters?
GLUT 1-brain, erythrocytes (no mitochondria), placenta, foetal tissue
GLUT 2-liver, kidney, intestine, pancreatic beta-cell
GLUT 3-brain
GLUT 4-muscle and adipose tissue (found in vesicle membranes)
GLUT 5-jejunum
How does insulin work with GLUT4?
Insulin binds to receptor and initiates the recruitment of GLUT4 to the cell surface by initiating a protein kinase cascade
How does insulin work with GLUT2?
· Insulin accelerates the uptake of blood glucose into the liver by GLUT2.
· The catalytic sites of glucokinase become filled with glucose – converting glucose to glucose 6-phosphate
· The increase in glucose 6-phosphate coupled with insulin action leads to a build-up of glycogen stores
Where is insulin produced?
produced by beta cells in the islets of langerhans
Where is glucagon produced?
produced by the alpha cells in the islets of langerhans
Where is gastrin produced?
secreted from G cells
Insulin______blood glucose whereas glucagon______blood glucose
Decreases
Increases
What is hypOglycemia
decrease in blood glucose so therefore stimulates glucagon.
What stimulates insulin secretion?
- high blood glucosse
- GIP and GLP-1 secretion from the intestine
What stimulates glucagon secretion?
- Low blood glucose
- rise in blood amino acids
What does glucagon do?
Acts on hepatocytes to stimulate glycogenolysis via GCPR, adenylyl cyclase, cAMP, protein kinase A cascade
· Inhibits fatty acid synthesis by reducing production of pyruvate (blocking glycolysis) and stimulates gluconeogenesis
What is type 1 diabetes?
Results in the beta cells of the pancreatic islets being lost because of an auto-immune process, hence meaning that little or no insulin is produced.
What is type 2 diabetes?
A condition where peripheral tissues are not responsive to insulin (insulin resistance)
The pancreatic beta cells initially compensate for insulin resistance by increasing production
What is the role of adrenaline in glucose level regulation?
· During a fasting period, adrenaline is released into circulation from adrenal glands
·promotes the breakdown of glycogen to glucose in skeletal muscle
· Lactate (conjugate base of lactic acid) is released and converted to glucose by the liver
What is the role of cortisol (glucocorticoids) in glucose level regulation?
· Secreted by the adrenal glands in prolonged fasting (form of stress)
· Cortisol supports the breakdown of glycogen and the conversion of amino acids, lactate, and glycerol to glucose in our liver
· Cortisol promotes protein breakdown of skeletal muscle – supplying amino acids to the liver to be converted to glucose
What are the hormones produced fro adrenal glands?
Aldosterone
Cortisol
Androgens
What are the 3 layers in the adrenal cortex?
Zona glomerulosa - Aldosterone
Zona fasciculata - Cortisol
Zona reticularis - Androgens
Boisynthesis of Aldosterone
· Angiotensin 2 binds to cells of the zona glomerulosa
· This causes Ca2+ to be produced as a second messenger
· This activates protein kinase C which converts cholesterol to pregnenolone
· Pregnenolone is then converted to progesterone then corticosterone in the mitochondria
· Corticosterone is converted aldosterone in the mitochondria – catalysed by K+
Biosynthesis of Cortisol
· ACTH binds GPCR on cells of the zona fasciculata – activating adenylyl cyclase
· ATP is converted to cAMP which activates PKA
· An LDL binds to an LDL receptor – which along with lipase and PKA converts a cholesterol ester to cholesterol
· In the mitochondria, cholesterol is converted to pregnenolone
· Pregnenolone is converted to 11 deoxycortisol in the cytoplasm
· This then moves back into the mitochondria where is converted to cortisol
· Cortisol leaves the cell and moves to target cells
How is the adrenal hormones regulated?
- There is a long term stress in the hypothalmus in the brain stimulates corticotrophin releasing hormone
- stimulates ACTH to be released in the anterior pituitary
- ACTH then goes into the blood stream and targets cells specifically in the cortex.
- These layers have cells that stimulate hormones.
Actions of cortisol
- provides a negative feedback to the brain
- hypERglycaemia
- Protein breakdown and lipolysis
- Gluconeogenesis
- Supression of Immune system
- Osteoclast stimulation
Actions of aldestrone
- important in increasing bp
- involved in the RAAS System
- stimuates water and sodium retension
Actions of Androgens
- promotes prostrate growth
- male characteristics like hair
- Female: sexual drive
What happens in the adrenal medulla?
It produced catecholamine hormones like adrenaline and nor adrenaline.
involved in the flight and fight response
- the hormones binds to proteins around the liver, lungs, digestive system, muscles
Name the insulin receptor?
Tyrosine Kinase Receptor
What components make tyrosine kinase receptor?
2 alpha subunits
2 betal subunits
2 TYR enzyme (needs to be phosphorylated to be active)
Describe the steps in the RAAS system?
· Dehydration, Na+ deficiency or haemorrhage cause a decrease in blood volume (and hence BP)
· This stimulates juxtaglomerular cells in the kidney to secrete renin (enzyme)
· Angiotensinogen is a plasma protein secreted by hepatocytes in the liver
· Renin converts angiotensinogen to angiotensin 1
· Angiotensin 1 is converted to angiotensin 2 by angiotensin converting enzyme (ACE) in the lungs
· Angiotensin 2 stimulates the adrenal glands (zona glomerulosa) to secrete aldosterone, the posterior pituitary to secrete ADH and vasoconstriction causing increased BP
Aldosterone:
· Increases cardiac output
· stimulates the kidneys to reabsorb Na+ and increases secretion of H+ and K+ into the urine (retension)
· vasconstricts ateries and arterioles
This is all to increase the blood pressure
What is the control mechanism for high calcium?
· High blood calcium stimulates parafollicular cells of the thyroid to secrete calcitonin
· Calcitonin inhibits osteoclast activity – so decreases blood calcium
What si the control Mechanism for Low Calcium?
· Low blood calcium stimulates chief cells of the parathyroid gland to secrete PTH
· PTH stimulates osteoclasts to resorb bone ECM – releasing calcium (and phosphate and magnesium) into the blood
· PTH also stimulates the kidneys to retain more calcium (and phosphate) from urine (but it increases phosphate loss)
· PTH also stimulates the kidneys to synthesise calcitriol (from vitamin D
Role of Vitamin D
· UV light converts 7-dehydroxycholesterol to vitamin D in the skin
· Vitamin D is also absorbed from the GI tract (via dietary sources)
· In the liver, vitamin D is converted to calcidiol via 25-hydroxylase
· Calcidiol is converted to the active calcitriol in the kidney – stimulated by PTH
· Calcitriol increases osteoclast activity and increases calcium uptake from the GI trac
What do sex steroids do?
steroid hormones either bind to the extracellular membrane with their transporter or binds directly to genetic material (nuclear hormone)
Testosterone Properties (Type of Androgen)
· Male sexual characteristics
· Stimulates libido in males and females
· Increases bone thickness and periosteal bone formation
· Increases basal metabolic rate and muscle mass
· Stimulates erythropoiesis (promoting RBC formation)
Oestrogen Properties
· Female primary and secondary sexual characteristics
· Energy homeostasis and metabolism
· Decreases bone resorption by osteoblasts and osteoclasts
· Decreases the risk of atherogenesis in males and females (atheroma formation)
FSH Properties
· Stimulates Sertoli cells in males – supports sperm maturation
· Growth and maturation of ovarian follicles
LH Properties
· Binds to Leydig cells (in males) – stimulating testosterone production
· Stimulates Theca cells (in females) to produce testosterone – which is then converted to oestrogen by adjacent granulosa cells (in the ovary)
Aromatase
· It catalyses the last steps of estrogen biosynthesis from androgens
· It transforms androstenedione to estrone and testosterone to oestradiol
Albumin
· Sex hormones are Lipophilic and therefore only weakly water soluble thus specialised transport of steroids in blood is used
· All steroids can be transferred via albumin
What is Hypogonadism?
reduction or absence of hormone secretion or other physiological activity of the gonads (testes or ovaries
What is Klinefelter’s Syndrome (Primary Hypogonadism)?
· Genotype – XXY (male)
· No early symptoms but can cause smaller genitalia, enlarge breasts and infertilit
What is Turner’s Syndrome (Primary Hypogonadism)?
· Genotype – X0
· Female genitalia present, no functional gonads, short stature, amenorrhea and delayed/absent puberty
What is Kallmann Syndrome (Secondary Hypogonadism)?
· Neurons that stimulate release of GnRH fail to migrate into hypothalamus during development
