Disorders of Appetite Flashcards
define polydipsia
excessive thirst
define adipsia
inappropriate lack or absence of thirst
(with consequent failure to drink in order to correct hyperosmolality)
define anorexia
lack or loss of appetite for food
define obesity
abnormal or excess fat accumulation that presents a risk to health
which thirst disorder is more common
polydipsia is more common than adipsia
secondary polydipsia is more common than primary most common causes of secondary polydipsia are diabetes insipidus and mellitus
what is secondary polydipsia
excessive thirst that is caused by a medical condition which disrupts any step in osmoregulation or ADH secretion
(primary polydipsia = psychogenic polydipsia)
what are the causes of secondary polydipsia
differentiate between how diabetes mellitus and diabetes insipidus cause polydipsia and their treatment
diabetes mellitus:
glucose in nephron exceeds the threshold which is able to be reabsorbed
glucose lowers water potential which draws more water to move into the nephron
produces high volume dilute urine
lots of water is being lost in the urine → polydipsia
treated using insulin to control blood sugar
much more common polydipsia cause
diabetes insipidus:
ADH secretion by posterior pituitary (cranial) is disrupted or collecting duct is not responsive (nephrogenic) to ADH
failure to reabsorb water → large volumes of dilute urine produced
treated with vasopressin
other than diabetes (mellitus and insipidus) what other medical conditions can cause polydipsia
acute kidney failure - can be due to hypoperfusion, toxins, medications, sepsis, urinary blockages
Conn’s syndrome - primary hyperaldosteronism, overproduction of aldosterone (controls K+ excretion and Na+ absorption and H2O retention) → hypokalaemia → tubular damage + renal tubule ADH resistance → polydipsia
addison’s disease – hypoadrenocorticism, reduced ability to concentrate urine depist normal kidney function
what are the symptoms of diabetes
polyuria
nocturia
polydipsia
paresthesia - in the extremities, later sign
blurred vision
fatigue
weight loss
acanthosis nigricans
infections - UTIs and skin
what are the causes of primary polydipsia
not an altered physiological state which leads to the excessive thirst
mental illness - psychogenic polydipsia
schizophrenia
mood disorders - depression and anxiety
anorexia
drugs - laxatives and diuretics (for congestive heart failure and fluid overload)
trauma to brain - especially where there is damage to ADH secreting area
organic brain damage
why is polydipsia a problem
how does it manifest clinically
electrolyte imbalance → hyponatremia (electrolyte imbalance has often already caused the problem)
and fluid overload → kidneys unable to keep up with passing the excess water
kidney and bone damage
headache
nausea
cramps
slow reflexes
slurred speech
low energy
conusion
seizures
what are the different types of adipsia
type a (most common)
type b
type c
type d
what is the underlying mechanism of adipsia
plasma osmolality increases (becomes hypertonic) → osmoreceptors shrink → increased activation of cation channels → depolarization → increased firing frequency → ADH secretion from posterior pituitary
there is increased ADH secretion → water retention but no feeling of thirst
what are eating disorders
give examples
Mental disorder defined by abnormal eating habits, includes:
Binge eating disorder – large amount of food over short period of time
Anorexia nervosa – eating very little due to fear of gaining weight
Bulimia nervosa - eat a large amount of food then purge via laxatives or vomiting
Pica – eating non-food items
Rumination syndrome – regurgitation of food
Avoidant/restrictive food intake disorder - eat a very limited selection of foods for psychological reasons (doesn’t involve fear about body shape or size)
eating disorders are increasing worldwide
how is anorexia defined
mild = BMI >17
moderate = BMI 16- 16.99
severe = BMI 15-15.99
extreme = BMI <15
what are the symptoms of anorexia
low BMI
continuous weight loss
amenorrhea
mood swings
dry hair
halitosis
skin and hair thinning
what is the underlying pathology of anorexia
combination of genetic, environmental, psychological and sociological causes of anorexia
serotonin involved → people with anorexia have higher levels of serotonin metabolites in CSF + they have abnormal response to serotonergic agents but recovering anorexics don’t
what are the co-morbidities associated with obesity
what will happen to obesity levels in future
why
increasing
51% of world’s population will be obese by 2030
not due to lack of exercise → physical activity was decreasing before obesity epidemic
due to increase in cheap calorie rich and nutrient poor beverages, sweets and fast food
how do we screen for obesity
measure height, weight + abdominal girth
history - diet and physical activity levels, psychosocial factors, weight gaining medications, familial traits
BMI of 30 or over, or 25 and over + co-morbidity should then be treated
emphasis is less on BMI and more on treating the co-morbidities
how can obesity be treated
diet + exercise
surgery:
sleeve gastrectomy
gastric bypass
who is eligible for bariatric surgery
how effective is bariatric surgery
people with BMI over 40 or 35+ with a comorbidity (hypertension, sleep apnoea, GORD, diabetes)
very effective → reduced all cause mortality and morbidity after bariatric surgery
weight loss after 5 years is 30-35% of body weight
high remission of co-morbidities:
diabetes - 80% remission
obstructive sleep apnoea = 80-85% remission
what are the physiological changes which occur after bariatric surgery
hormones involved:
GLP1 and GLP2 - produced by enteroendocrine L cells, increase insulin secretion + decrease glucagon secretion + inhibits gastric motility and secretion
ghrelin - produced by stomach, stimulates appetite by activating NPY orexigenic hormones
PYY - released from ileum + colon, reduces appetite by acting on POMC neurons
after bariatric surgery:
GLP1 and GLP2 and PYY levels increase - type 2 diabetes goes into remission (increased insulin secretion + sensitivity) and there is reduced appetite
ghrelin levels decrease - stomach is smaller → becomes full quicker → ghrelin decreases → appetite decreases
