Endorine Flashcards
what is the difference between water/fat soluble hormones?
water - unbound, bind to cell surface receptor, short halfe-life, fast clearance eg protein
fat - protein bound to transport, diffuse into cell, long half-life, slow clearance eg steroid, thyroid
what is endocrine vs paracrine vs auto crine hormones?
Endocrine – blood-borne, acting at distant sites
Paracrine – acting on adjacent cells
Autocrine – feedback on same cell that secreted hormone
what are the classes of hormones?
peptides
amines
Iodothyronines
Cholesterol derivatives and steroids
how is hormone secretion controlled?
basal secretion - continuous or pulsatile
superadded rhythms - eg day night ACTH
Release inhibiting factors – dopamine inhibiting prolactin
releasing factors
what determines the action of hormones?
Hormone metabolism – increased metabolism to reduce function
Hormone receptor induction – induction of LH receptors by FSH in follicle
Hormone receptor down regulation – hormone secreted in large quantities cause down regulation of its target receptors
Synergism – combined effects of two hormones amplified (glucagon with epinephrine)
Antagonism - one hormone opposes other hormone (glucagon antagonizes insulin)
how are peptide hormones stored?
granules
what is the definition of anorexia?
lack of appetite
what are the BMI ranges classified as?
<18.5 underweight
18.5 - 24.9 normal
25.0 - 29.9 overweight
30.0 - 39.9 obese
>40 morbidly obese
what are some risks of obesity?
Type II diabetes
Hypertension
Coronary artery disease
Stroke
Osteoarthritis
Obstructive sleep apnoea
Carcinoma
what part of the body regulates appetite?
hypothalamus
what gut peptides affect appetite?
CCK
Ghrelin
PYY
what is leptin responsible for?
switching off appetite
what are the blood levels of leptin after eating?
increased
what central controllers increase appetite?
NeuroPeptideY
MCH - Melanin-Concentrating Hormone
AgRP - Agouti-related peptide
Orexin
endocannabinoid
what central controllers decrease appetite?
alpha-MSH
CART - cocaine and amphetamine regulated transcript
GLP-1
seretonin
what does peptide YY do?
inhibits gastric motility - reducing appetite
how does CCK affect appetite?
delays gastric emptying
gall bladder contraction
insulin release
- satiety via VAGUS nerve
what does Ghrelin stimulate?
Growth hormone release
appetite - orexigenic
how do leptin and insulin work in appetite?
- Stimulate- POMC/CART neurons increase CART and alpha-MSH levels
- Inhibit NPY/AgRP neurons, so decrease NPY and AgRPNet effect : increase Satiety and decrease Appetite
how does ghrelin work?
stimulates NPY/AgRP, increase NPY and AgRP secretion
↑ Appetite
what cells secrete peptide YY?
neuroendocrine cells in ileum, pancreas and colon
in response to food
what are the effects of incretin?
- blunting glucagon
- beta-cell stimulation of insulin production
- improved satiety
- decreased gstric motility
where does glucose come from in the fasting state?
glycogen breakdown and gluconeogenesis from liver
little bit from kidney
in the fasting state what are the insulin levels?
low
where does glucose go after ingestion (and percentage)?
40% to liver
60% to periphery, mostly muscle
what secretes insulin and glucagon?
islets of langerhans
what cells secrete insulin and glucagon?
beta - insulin
glucagon - alpha
what are the steps of insulin release from a cell?
glucose entry into cell by GLUT2 glucose transporter
glucokinase causes phosphorilation
K+ channels close - depolarisation
calcium channels open and ca2+ enters cell
insulin is released
what is the action of insulin in muscle and fat cells?
GLUT4 integrates into membrane and glucose enters cell
what are counterregulatory hormones of insulin?
glucagon
and adrenaline
(cortisol and growth hormones but take long time)
what is diabetes mellitus?
disorder of carbohydrate metabolism characterised by hyperglycaemia
what complications are associated with diabetes?
diabetes retinopathy
diabetic nephropathy
stroke
cardiovascular disease
diabetic neuropathy
what are the types of diabetes?
type 1
type 2 - includes gestational and medication induced
monogenic diabetes - youth
pancreatic
endocrine
malnutrition related
what plasma glucose levels show diabetes?
> 11mmol/l
or >7mmol/l when fasting
what does HbA1c measure and show?
haemoglobin attachment to glucose
>48mmol/mol is diabetic
what is the definition of type 1 diabetes?
An insulin deficiency disease characterised by loss of beta cells due to autoimmune destruction
what does failure of insulin secretion lead to?
Continued breakdown of liver glycogen
Unrestrained lipolysis and skeletal muscle breakdown providing gluconeogenic precursors
Inappropriate** increase in hepatic glucose output **and suppression of peripheral glucose uptake
what is the renal thershold of glucose?
10mM
what happens when type 1 diabetes isnt treated with insulin?
- Increase in circulating glucagon
- further increasing glucose
perceived ‘stress’ - increased cortisol and adrenaline
- progressive catabolic state
- increasing levels of ketones
what is type 2 diabetes?
- impaired insulin secretion or insulin resistance
- causing impaired glucose tolerance
- progressive hyperglycaemia and high free fatty acids
what happens to glucose disposal rate in type 2 diabetes?
becomes lower
what does impaired insulin action in type 2 diabtes lead to (metabolically?
high circulating free fatty acids
abnormally high glucose output after a meal
(no weight loss or ketones like in type 1)
what causes both glycosuria and ketonuria?
type 1 diabetes
what is treatment for type 2 diabetes?
- lifestyle - weight loss, exercise
- medication - metformin, Sulfonylureas, DPP4 etc..
- management of BP and lipids
what do sulphonylureas do?
stimulate insulin release by binding to beta receptors
- can cause weight gain and hypoglycaemia
eg - gliclazide, glibenclamide
what do thiazolidinediones do?
improve insulin sensitivity
- rarely used due to side effects like weight gain
(used in type 2)
what secretes GLP-1?
L cells in intestine
what do SGLT2 inhibitors do?
block glucose reabsorption - more glucose excreted in urine
what medication is used for type 2 diabetes?
metformin first line
DPP-IV inhibitors, GLP1 analogues, SGLT-2 inhibitors
give examples of GLP-1 analogues
(stimulate insulin secretion, inhibit glucagon production)
Exenatide(BYETTTA) twice daily
Once weekly exenatide (BYDUREON)
Liraglutide (VICTOZA) once daily
Lixisenatide (LYXUMIA) once daily
Dulaglutide (TRULICITY) once weekly
Semaglatide (OZEMPIC) once weekly
Oral semaglutide (RYBELSUS) daily
when does diabetes ketoacidosis occur in type 2 diabetes?
It is rare because the low insulin levels are sufficient to suppress catabolism and prevent ketogenesis.
It can occur if hormones such as adrenaline rise to high levels (eg during an MI)
what is the difference in insulin in type 1 and 2 diabetes?
1 - Profound insulin deficiency
2 - Insulin resistance, Impaired insulin secretion and progressive β-cell damage but initially continued insulin secretion
what are the Different insulin approaches in diabetes?
once-daily basal insulin - only in type 2 - mimics pancrease, longer acting
twice-daily mix-insulin - both
basal-bolus therapy - mostly type 1 - after eating
what are the 2 levels of hypoglycaemia?
1 - Alert value
Plasma glucose <3.9 mmol/l (70 mg/dl) and no symptoms
2 - Serious biochemical
Plasma glucose <3.0 mmol/l
(55 mg/dl)
what are some of the effects of hypoglycaemia on the body?
brain - cognitive dysfunction, seizures,comas
heart - increased risk of myocardial ischaemia
circulation - inflammation, blood coagulation abnormality
musculoskeletal - falls, fractures
what are some autonomic symptoms of hypoglycaemia?
trembling
palpitations
sweating
anxiety
hunger
what are some neuroglycopenic symptoms of hypoglycaemia?
confusion
weakness
drowsiness
vision changes
difficulty speaking
difficulty concentrating
at what blood glucose level do hypoglycaemia most commonly cause symptoms?
under 3.9mmol/l
- can be higher in patients with poor glycaemic control with elavated HbA1c
how is hypoglycaemia treated?
- 15g of fast acting carbohydrate to relieve symptoms
- glucagon injection/ IV dextrose if unable to swallow
- Eat a long-acting carbohydrate to prevent recurrence of symptoms
why is it important to retest glucose levels in hypoglycaemia?
to make sure blood glucose is over 4mmol/l and retreat if needed
what are some risk factors that screening for hypoglycaemia is based of?
Low HbA1c; high pre-treatment HbA1c in T2DM
Long duration of diabetes
A history of previous hypoglycaemia
Impaired awareness of hypoglycaemia (IAH)*
Recent episodes of severe hypoglycaemia
Daily insulin dosage >0.85 U/kg/day
Physically active (e.g. athlete)
Impaired renal and/or liver function
what are some causes of hypoglycaemia?
- taking higher levels of antidiabetic medications
- antimalarial drugs
- hormone deficiency eg cortisone
- skipping meals
over exercising - excess alcohol
what are some of the effects of the parathyroid hormone?
- increased Ca2+ reabsorption, decreased phosphate reabsorption
- increased hydroxylation of 25-OH vit D - increases Ca2+ absorption
- increased bone resorption
how do you work out correct calcium levels in the blood?
total serum calcium + 0.02 * (40-serum albumin)
what signs does hypoglycaemia cause?
- parathesia
- muscle spasm
- seizures
- basal ganglia calcications
- cataracts
- ECG abnormalities - long QT interval
- chvosteks sign and trousseaus sign
what is the chvosteks sign and trousseaus sign?
chvosteks sign - spasm of facial muscle when tapping over facial nerve
trousseaus - inflation of BP cuff to 20mmHg above systolic for 5 min - flexion of wrist andadduction of thumb, extension of IP joints
- show low calcium
what are the causes of hypocalcaemia?
- low vit D intake
- hypoparathyroidism
eg due to
surgery, radiation
syndromes - Di George, HDR, Kenney-Caffey
genetic , autoimmune
infiltration - haemochromatosis, Wilsons disease
magnesium deficiency - pseudohypoparathyroidism
what is pseudohypoparathyroidism?
resistance to parathyroid hormone
- type 1 albright hereditary ostodystophy
- mutation with deficient Galpha subunit 1a
what are the symptoms of hypercalcaemia?
- thirst
- nausea
- constipation
- confusion - later coma
- renal stones
- ECG abnormalities - Short QT
what are the most common causes of hypercalcaemia?
malignancy
primary hyperparathyroidism
what is a way to rememeber consequences of primary hyperparathyroidism?
BONES - osteitis fibrosa cystica, osteoporosis
STONES - kindey stones
GROANS - confusion
MOANS - constipation - acute pancreatitis
what are the main causes of primary hyperparathyroidism?
80% due to single benign adenoma
12-20% due to four gland hyperplasia (may be MEN1/2)
rarely malignant
what is the normal range of PTH in blood?
14 to 65 pg/mL
what are normal calcium levels?
2.2 to 2.6 millimoles per litre (mmol/L)
what are the hormones released by the hypothalamus and piuitary gland?
*GHRH & SMS
* GnRH
* CRH
* TRH
* Dopamine
Pituitary
* GH
* LH & FSH
* ACTH
* TSH
* Prolactin
what causes some pituitary gland conditions?
- Benign pituitary adenoma
- Craniopharygioma - tumours
- Trauma
- Apoplexy / Sheehans - severe bleeding
- Sarcoid / TB - inflammation
what do pituitary tumours cause?
- pressure on local structures eg optic chiasm - bitemporal hemianopia
- pressure on pituitary - hypopituitarism
- functioning tumour - prolactinoma, acromegaly, cushings disease
what is precocious puberty?
onset of secondary sexual characteristics before 8 for girls and 9 for boys
what is delayed puberty?
absence of secondary sexual characteristics by 14 for girls and 16 for boys
what can delayed puberty lead to?
reduced peak bone mass and osteoporosis
delay in secondary sex characteristics
psychological problems
defects in reproduction
what reactivates GnRH pulse generator in puberty?
GPR54
what is the difference between precocious puberty and precocious pseudopuberty?
true - stimulated LH:FSH ratio >1
pseudo - LH:FSH <1
what is precocious puberty treated with?
GnRH super-agonist to suppress LH and FSH secretion
what causes precocious puberty?
CNS tumours
CNS disorders
what causes precocious pseudopuberty?
Increased androgen secretion
gonadotropin secreting tumours
McCune-albright syndrome
ovarian cyst
oestrogen secreting neoplasm
hypothyroidism
latrogenic or exogenous sex hormones
what signs in girls indicate need for investigation for delayed puberty?
- Lack of breast
development by 13 yrs - More than five years
between breast
development and
menarche - Lack of pubic hair by age
14 yrs - Absent menarche by age
15-16 yrs
what signs in boys indicate need for investigation for delayed puberty?
- Lack of testicular
enlargement by age 14
yrs - Lack of pubic hair by age
15 yrs - More than 5 years to
complete genital
enlargement
what is an example of primary hypogonadism?
testes/overies failing = low test/prog/oest = LH/FSH increase
eg Klinefelter syndrome in males
what is an example of secondary hypogonadism?
hypothalamus/pituitary failing - LH/FSH are low
what does kallmanns syndrome and prader-willi syndrome cause?
hypogonadotrophic hypogonadism
what causes hypergonadotrophic hypogonadism in males/females?
males - klinefelters syndrome
females - turners syndrome
what is given to males/females for replacement therapy?
males - testosterone enanthate - IM injection 2-4 years
females - ethinyl estradiol tablets or oestrogen - starting with low does for gradual growth, once full replacement dose achieved, progesterone is added
what is constitutional delay of growth and puberty?
- diagnosis of exclusion
- delayed puberty, delayed bone age, short stature
what are the secondary sexual characteristics of puberty for boys/girls?
boys - external genitalia and pubic hair growth
enlargement of larynx and laryngeal muscles
girls - growth of breast and female genitalia (ovarian oestrogens) and pubic and axillary hair growth (ovarian/adrenal androgens)
where is vasopressin and oxytocin made in posterior pituitary?
paraventricular nucleus
supraoptic nucleus
what vasopressin receptors are found in a) vasculature, b) renal collecting tubules, c) pituitary gland
v1a
v2
v1b
what is vasopressin release controlled by?
osmoreceptors in hypothalamus
baroreceptors in brainstem and vessels - emergencies
what happens after water ingestion?
plasma osmolarity decreases
vasopressin secrertion decreases
urine water excretion increases
where does ADH bind to work on the kidneys?
v2 receptors in collecting duct principle cells
what is normal osmolarity?
282-295 mOsmol/Kg
what is cranial diabetes insipidus characterised by?
lack of vasopressin
what is nephrogenic diabetes insipidus characterised by?
resistance to vasopressin
what is SIAD?
syndrome of anti-diuretic hormone secretion
- too much vasopressin released
- common
what are features of diabetes insipidus?
polyuria - excessive urine production
polydypsia - extreme thirst
no glycosuria - glucose in urine
what are the causes of nephrogenic DI?
familial - rare
- x-linked - v2 receptor defect
- autosomal - aquaporin 2 defect
acquired - reduction in medullary conc gradient or antagonism of effects of AVP
- eg drugs, chronic renal impairment, metabolic
how is AVP deficiency (cranial DI) treated?
desmopressin
- treat any underlying conditions
what can be used to measure AVP concentartion?
copeptin
how is AVP resistance (nephrogenic DI) treated?
- avoiding precipitating drugs
- congenital - very hard
- free acces to water and very high dose desmopressin