Endocrine system Flashcards
what are the components of the endocrine system
pituitary, thyroid, parathyroid, adrenal glands, pancreas, ovary/testes
endocrine vs exocrine glands
endocrine –> secretions into blood
exocrine –> secretion into ducts
what are paracrine and autocrine actions
paracrine –> acts on adjacent cells
autocrine –> acts on cell which secreted hormone
water soluble hormones vs fat soluble hormones
water soluble
- travels unbound
- binds to surface receptor of interactions
- short half life
- fast clearance
fat-soluble
- travels by protein binding
- diffuses into cell for interactions
- long half life
- slow clearance
give an example of a peptide hormone
insulin, LH, FSH
what are characteristics of peptide hormones (polarity, storage and release)
hydrophilic
stored in secretory granules
released in pulses or bursts
what is proinsulin made of
C-peptide and insulin joined by cystine bonds
How does the insulin receptor work
binding of insulin to the alpha domain leads to phosphorylation of tyrosine kinase and leads to cascade reactions which drive glucose uptake
what type of hormone is dopamine
amine
what do you call thyroid hormones
iodothyronines
how is thyroid hormone synthesised and released
SYNTHESIS
thyroid follicular cells secrete thyroglobulin into colloid
iodine gets incorporated in thyroglobulin –> iodothyrosines
conjugation of iodotyrosines gives rise to T3 and T4
RELEASE
hypothalamus produces thyrotropin releasing hormone
this causes pituitary to release thyroid stimulating hormone
TSH binds to TSHR (receptor) and stimulates movement of colloid into follicular cell where T4 and T3 get cleaved from thyroglobulin
which is the active form? iodide or iodine
iodine
iodide –> dide for DEAD
how do nuclear receptor hormones work? give examples
they directly bind to DNA and affect transcription –> they function as transcription factors
Oestrogen, Thyroid Hormone, Vitamin D
what transports Vit D and How does it function as a hormone
it is transported by Vit D binding protein
it enters the cell directly in the nucleus to stimulate more absorption of calicum and phosphate
how do steroid hormones act?
diffuse through plasma membrane (hydrophobic)
bind to receptor
receptor hormone complex enters nucleus and binds to GRE
binding to a DNA region promotes transcription of that gene to mRNA
mRNA leads to protein synthesis
which hormones have a circadian rhythm
cortisol
prolactin
GH
LH
FSH
melatonin
what hormones are secreted by the posterior pituitary
oxytocin and ADH
what are the functions of oxytocin
lactation and uterus/cervical dilation
if a patient has abnormal hormonal tests what is the next test you would perform
MRI of pituitary
what are the functions of growth hormone
growth promotion and metabolism
what effect does growth hormone have on insulin and why
inhibiting –> promotes fat and carbohydrate metabolism
what effect does GH have on blood glucose
increase blood glucose
what effect does GH have on the liver and other tissues
Production of IGFs (insulin like growth factors)
leads to cell proliferation and cell growth
draw the HPT axis
hypothalamus > TRH . ant pituitary > TSH > Thyroid gland > Thyroid hormones > Target cells
negative feedback loops:
TSH inhibits hypothalamus and Thyroid hormones inhibit the ant pituitary and the hypothalamus
what is the blood supply of the thyroid
Inferior thyroid artery from the subclavian thyrocervical trunk
Superior thyroid artery from the external carotid
In some people there is also the IMA artery from the brachiocephalic trunk
what are the functions of the thyroid hormone
Accelerates food metabolism
Increases protein synthesis
Stimulation of carbohydrate and fat metabolism
Increase in ventilation rate, CO and HR
Brain development during foetal life and postnatal development
Growth rate accelerated
draw the HPA axis
hypothalamus > CRH > Ant pituitary > ACTH > Adrenal cortex > cortisol
Negative feedback loop:
Cortisol inhibits both the Ant pituitary and the Hypothalamus
functions of cortisol
increase metabolism of glucose (diabetes! - cortisol increases blood sugar)
control your blood pressure
reduce inflammation
what are the layers of the adrenal gland
capsule
zona glomerulosa
zona fasciulata
zona reticularis
adrenal medulla
what do the specific areas of the adrenals secrete
CORTEX
Zona glomerulosa (mineralocorticoids)
aldosterone
Zona fasciculata (glucocorticoids)
cortisol
Zona reticulata (androgens)
adrostenedione
DHEA
MEDULLA (catecholamines)
Epinephrine and Norepinephrine
what is the short term vs the long term response to stress in terms of hormone secretion
short-term –> epinephrine and norepinephrine (catecholamines)
long-term –> mineralocorticoids and glucocorticoids (aldosterone and cortisol)
all of these lead to increased blood glucose, immune suppression and increase in blood volume and blood pressure
what is the hormone produced by the heart and what does it do
ANP
decreases BP by promoting Na and H2O excretion
VASODILATION
also dilates afferent arteriole to increase GFR
where is IGF-I synthesised
Liver
where is erythropoietin synthesised
kidney
what hormones do blood vessels secrete
endothelin
NO
prostaglandins
what is the BMI formula
wt (kg)/ht (m2)
what are the BMI ranges
<18.5 underweight
18.5 - 24.9 normal
25.0 - 29.9 overweight
30.0 - 39.9 obese
>40 morbidly obese
what are the risks of obesity
Type II diabetes
Hypertension
Coronary artery disease
Stroke
Osteoarthritis
Obstructive sleep apnoea
Carcinoma
- Breast
- Endometrium
- Prostate
- Colon
what parts of the brain play a role in appetite regulation and what exactly do they control
lateral hypothalamus –> hunger
ventromedial hypothalamic nucleus –> satiety centre
what things control appetite
psychological factors
cultural factors
neural afferents –> vagus
Hormones like leptin insulin and cortisol
glucose and ketones
CCK
Ghrelin
where is leptin secreted from and what is its function
white adipose tissue
Switches off appetite and is
immunostimulatory
what is the function of peptide YY, what is it secreted by, and on what receptors does it act
binds to NPY receptors and secreted in response to food to inhibit gastric motility and appetite
secreted by neuroendocrine cells in the ileum pancreas and colon
what is the function of CCK and where are its receptors
receptors: pyloric sphincter
function:
- delays gastric emptying
- contracts gall bladder
- stimulates insulin release
draw the cycle of neurohormonal regulation of eating
look at appetite regulation slides
where is ghrelin expressed and what is its function
expressed in stomach and stimulates GH release and increases appetite
what are the functions of incretins
Reduce glucagon only when blood sugar is NORMAL OR HIGH, not when it’s low.
Boost insulin production only when blood sugar is HIGH, avoiding drops in blood sugar.
They improve the feeling of fullness after eating, aiding in appetite control.
They slow down the movement of food from the stomach to the intestine, helping control blood sugar spikes after meals.
what is the site of insulin and glucagon secretion
islet of langerhans
Beta cells - insulin
alpha cells - glucagon
what cells secrete somatostatin and PP (pancreatic polypeptide)
All cells are in the Islets of langerhans
Delta cells - somatostatin
F cells - Pancreatic polypeptide
explain the metabolism of carbohydrates in the fasting state
you get glucose via breakdown of glycogen and gluconeogenisis
glucose is used by important things like rbc and brain
insulin levels are low
muscles use free fatty acids for fuel
what is the relationship between alpha and beta cells in the islets of langerhans
they are glucagon and insulin secreting respectively and they are right next to each other so that they can have paracrine crosstalk and inhibit each other
ex.: local insulin release will inhibit glucagon release
explain the insulin secretion by the beta cell
1) glucose enters beta cell via GLUT 2 transporter
2) glucose metabolism forms ATP which leads to a conformational change in the Kir6.2 channel –> channel closes
3) Kir6.2 normally allows K+ diffusion in the cell so when the channel is closed the beta cell becomes depolarised which allows Ca+2 channels to open
4) opening of Ca+2 channels triggers insulin vesicle exocytosis
how does insulin act on muscle and fat cells
activation of insulin receptors triggers mobilisation of vesicles with GLUT4 channel prot to the plasma membrane –> more channel prot allows for more “doors” for glucose entry in the cell –> accelerates diffusion of glucose into cell
what are the functions of insulin
Supresses hepatic glucose output
decreases Glycogenolysis
decreases Gluconeogenesis
Increases glucose uptake into insulin sensitive tissues (muscle, fat)
supress Lipolysis
surpress Breakdown of muscle
what are the functions of glucagon
Increases hepatic glucose output
increases Glycogenolysis
increases Gluconeogenesis
Reduces glucose uptake into tissues (cuz you want more in blood)
Stimulate peripheral release of gluconeogenic precursors (glycerol, AAs)
Lipolysis
Muscle glycogenolysis and breakdown
what are the consequences of acute and chronic hyperglycaemia in diabetes mellitus
Acute hyperglycaemia which if untreated leads to acute metabolic emergencies:
- diabetic ketoacidosis (DKA)
- hyperosmolar coma (Hyperosmolar Hyperglycaemic State )
Chronic hyperglycaemia leading to tissue complications (macrovascular and microvascular) neuropathies, nephropathies, retinopathies
what are possible complications of diabetes
diabetic retinopathy –> vision loss
diabetic nephropathy –> Kidney failure
stroke
CVD
Diabetic Neuropathy –> loss of sensation in extremities; amputations
what is the most common cause of death and disability in diabetics
CVD
what are the types of diabetes
Type 1
Type 2
Includes gestational and medication induced diabetes
Maturity onset diabetes of youth (MODY), also called monogenic diabetes
Pancreatic diabetes
“Endocrine Diabetes” (Acromegaly/Cushings)
Malnutrition related diabetes
what are the blood tests for diabetes and what values indicate diabetes
Random plasma glucose > 11 mmol/l
Fasting plasma glucose > 7 mmol/l
GTT (Glucose Tolerance Test) - after fasting glucose test you give patient a drink of glucose solution - after 2h measure value > 11 mmol/l (repeated on 2 occasions)
HbA1c (glycated hemoglobin- is a measure of average blood sugar levels over the past 2-3 months) of > 48mmol/mol (6.5%)
what is the pathophysiology of type 1 diabetes
loss of beta cells due to autoimmune destruction leads to insulin deficiency
autoimmune response is because beta cells express HLA antigens which results in chronic cell mediated immune response –> chronic insulitis
what are the results of insufficient insulin secretion
Uncontrolled breakdown of glycogen from liver, fats and muscles, providing materials for glucose production.
Liver produces more glucose while peripheral uptake decreases.
High glucose levels prompt excess glucose loss in urine (exceeding renal threshold).
what does failure of insulin treatment in type 1 diabetes lead to
Increased circulating glucagon due to reduced local insulin effects.
Stress responses trigger elevated cortisol and adrenaline levels.
Progression into a catabolic state with rising ketone levels.
what is IGT
IGT stands for Impaired Glucose Tolerance, which is a condition where blood sugar levels are higher than normal but not high enough to be classified as diabetes. It’s often considered a pre-diabetic state.
why does type 1 diabetes result in ketoacidosis and type 2 diabetes is much less likely to
Ketone Production in Type 1 Diabetes:
Insulin shortage due to immune attack on pancreatic beta cells.
Glucose can’t be effectively used for energy without sufficient insulin.
Body compensates by breaking down fats for energy.
Result: Ketone production (acetoacetate, beta-hydroxybutyrate, acetone).
Difference in Type 2 Diabetes:
Type 2 involves insulin resistance but still has insulin production; even a little bit of insulin help to prevent ketogenisis
type 1 vs type 2 diabetes
type 1 is characterised by absent insulin production
type 2 is characterised by insulin RESISTANCE and progressive failure of insulin secretion
what causes the insulin resistance in type 2 diabetes
Genetic predisposition
Environmental factors (obesity and lack of physical activity)
Lipid deposition in liver and pancreas lead to both insulin resistance and impaired insulin secretion
how do you treat type 2 diabetes
weight loss and exercise which if substantial can reverse hyperglycaemia
BP medication and blood glucose and lipids medications
metmorphin –> Reduce gluconeogenesis in liver (gluconeogenesis increased in T2DM due to excess glucagon)
sulphonylureas –> medications which stimulate insulin release and improve glycaemic control but at the expense of weight gain
Glitazone (aka thiazolidinediones) –> Enhance uptake of fatty acids & glucose by improving insulin sensitivity but increase weight, risk of heart failure, and risk of fractures
DPP4 Inhibitors - prolong effect of GLP-1
what is GLP-1, who is it secreted by and what is its function
glucagon-like peptide
it is an incretin
secreted by L cells in intestine
stimulates insulin secretion and
suppresses glucagon
slows gastric emptying
reduces appetite
improves insulin sensitivity
what is basal bolus therapy
it is a diabetes therapy which uses two types of insulin: basal insulin and bolus insulin
basal insulin provides a constant background insulin level which helps control blood sugar levels between meals
bolus insulin is fast acting and it is usually taken after meals to handle the rapid surge in blood glucose
how are basal bolus insulin levels throughout the day different to insulin levels in a normal person
slow increase in insulin levels after subcutaneous injections and slower decline in insulin levels following meals
what are the advantages and disadvantages of basal insulin in type 2 diabetes
advantages
Simple for the patient, adjusts insulin themselves based on fasting glucose measurements (personalization of dose)
Carries on with oral therapy, combination therapy is common
Less risk of hypoglycemia at night
disadvantages
Doesn’t cover rise in blood sugar after meals
Best used with long-acting insulin analogues which are considered expensive.
advantages and disadvantages of pre-mixed insulin in diabetes
Advantages
- Both basal and prandial components in a single insulin preparation
- Can cover insulin requirements through most of the day
Disadvantages
- Not physiological
- Requires consistent meal and exercise pattern
- Comes as a fixed mix –> can’t change dose of different components
- increased risk for nocturnal hypoglycaemia
- increased risk for fasting hyperglycaemia if basal component does not last long enough
- Often requires accepting higher HbA1c goal of <7.5% or ≤8% (<58 or ≤64 mmol/mol)2,3
what are the differences between T1DM and T2DM treatment
Oral medications are not typically part of the treatment regimen for type 1 diabetes. Basal-bolus therapy is used.
Oral medications are often a first-line treatment for type 2 diabetes. Basal -bolus only used as disease progresses.
what is the difference between severe and non-severe hypoglycaemia
severe - Patient has impaired cognitive function sufficient to require external help to recover; plasma glucose in less than 3 mmol/l
non-severe - Patient has symptoms but can self-treat and cognitive function is mildly impaired; plasma glucose is less than 3.9 mmol/l
what are complications of hypoglycaemia
Brain - cognitive disfunction - seizures, comas
Heart - increased risk of miocardial ischemia and cardiac arrhythmias
Circulation - endothelial dysfunction and inflammation; blood coag abnormalities
Muscle Weakness - Due to decreased energy supply, interruption of nerve signalling, and release of adrenalin
common symptoms of hypoglycaemia
AUTONOMIC:
Trembling
Palpitations
Sweating
Anxiety
Hunger
NEUROGLYCOPENIC:
Difficulty concentrating
Confusion
Weakness
Drowsiness, dizziness
Vision changes
Difficulty speaking
NON-SPECIFIC:
Nausea
Headache
what are the physiological responses to preventing hyperglycaemia
Inhibition of endogenous insulin secretion
Secretion of glucagon and adrenaline
what are the causes of hypoglycaemia?
Long duration of diabetes
Tight glycaemic control with repeated episodes of non-severe hypoglycaemia
Increasing age
Increased physical activity
Sleeping
Use of drugs and alcohol
Not eating
how do you treat hypoglycaemia?
15 g fast-acting carbohydrate to relieve symptoms
retest blood in 15 minutes to ensure blood glucose levels > 4.0 mmol/L
Eat a long-acting carbohydrate to prevent recurrence of symptoms
why does hypoglycaemia happen to diabetics from a physiological perspective?
Hypoglycaemia occurs due to the inability of insulin therapy to mimic the physiology of the beta cell
what are the functions of the parathyroid hormone?
increased gut Ca+2 ABSORPTION and renal Ca+2 REabsorption
phosphate excretion
increased Vit D3 levels for increased Ca+2 absorption
Decrease FGF-23
increased bone RESORPTION
what is the response of PTH to decreased serum calcium?
increase in PTH secretion to enhance Ca+2 absorption via gut, reabsorption via the renal system, and resorption from bone stores.
Vit D synthesis also increases to aid intestinal absorption of Ca+2
Phosphate excretion increases because phosphate and calcium are tightly coupled in bone tissue. When PTH stimulates bone resorption, calcium and phosphate are uncoupled and released into the bloodstream. The PTH will increase Ca+2 reabsorption and decrease PO4-3 reabsorption.
why is calcium homeostasis important?
functioning of muscles and nerves (heart muscle, skeletal muscle, and nerve impulses depend on calcium movement)
why do you have to be careful with serum calcium readings?
because the serum calcium reading includes both free-floating ionised calcium which is active and the calcium which is albumin-bound. If you have a low serum calcium reading it might actually just be due to hypoalbuminemia, not necessarily low active calcium levels in the blood. Your active calcium levels might still be normal.
what are the consequences of hypocalcaemia?
paresthesia
muscle spasm
seizures
basal ganglia calcification
cataracts
ECG abnormalities
long QT intervals
what is Chvostek’s sign and how is it tested
A positive Chvostek’s sign, which is characterized by facial twitching in response to tapping the facial nerve in front of the ear, can be indicative of hypocalcemia in some cases.
This sign is one of the clinical manifestations of hypocalcemia, suggesting increased neuromuscular irritability due to low blood calcium levels. When the facial nerve is tapped in individuals with hypocalcemia, it can trigger involuntary muscle contractions or twitching in the facial muscles.
what is Trousseau’s sign and how is it tested
Trousseau’s sign is a clinical sign used in medicine to indicate increased neuromuscular irritability associated with hypocalcemia
The sign is elicited by inflating a blood pressure cuff on the arm to a pressure higher than the systolic blood pressure for a few minutes. This occlusion of blood flow can result in ischemia to the tissues below the cuff. In individuals with hypocalcemia, this brief ischemic episode can trigger involuntary muscle twitching or spasms which might cause flexion of the wrist, thumb and metacarpophalangeal joints, resulting in a characteristic hand posture resembling a claw or “paddle-shaped” hand.
*there is no flexion of the interphalangeal joints
what are the possible causes of hypocalcaemia?
vit d deficiency
hypoparathyroidism
pseudohypoparathyroidism
what are the causes of hypoparathyroidism?
surgical
radiation
Di George syndrome –> developmental abnormality which leads to many congenital defects
Genetic cause
Autoimmune
Magnesium deficiency
very rare but could also be due to hemochromatosis and Wilson’s disease cuz they are characterised by increased iron and copper depositions respectively which could affect the parathyroid gland
what is pseudohypoparathyroidism
resistance to PTH
why might keeping the tourniquet on for too long ruin the blood results
Prolonged use of a tourniquet during blood collection can cause hemoconcentration due to restricted blood flow. This can lead to an increase in blood components like proteins and electrolytes, affecting certain blood test results. Additionally, hemoconcentration from restricted blood flow might trigger muscle breakdown, releasing substances like calcium, potassium, myoglobin, and creatine kinase into the bloodstream, and potentially altering blood test values.
what are the complications of hypercalcaemia?
thirst
polyuria
nausea
constipation
confusion -> coma
renal stones
ECG abnormalities
short QT interval
what are the causes of hypercalcaemia?
90% of cases are due to:
Primary hyperparathyroidism
OR
Malignancy - causes unregulated bone breakdown leading to increased calcium levels in the blood
Non-Hodgkin’s Lymphoma
Myeloma
Bone metastases and production of local factors that mobilise calcium
PTHrP – Parathyroid Hormone relating peptide, occurs in some kidney and lung cancers, behaves similarly to PTH but isn’t measured on assay
adrenal insufficiency can also be a cause
what are the consequences of primary hyperparathyroidism?
bones, stones, groans, moans
Bones - osteitis fibrosa cystica and osteoporosis
Stones - kidney stones
Psychiatric groans - confusion
Abdominal moans - Nausea, Vomiting, Constipation, Indigestion
also possible cardiac arrest
what are the causes of primary hyperparathyroidism?
80% due to single benign adenoma
15-20% due to four gland hyperplasia
what is the difference between hypoparathyroidism vs pseudohypoparathyroidism?
Hypoparathyroidism = insufficient production or secretion of PTH
Pseudohypoparathyroidism = rare genetic disorder where the body exhibits resistance to the action of PTH