endocrinology part 2 Flashcards
specific ACTH receptor to which ACTH can bind to are found on?
zona fasciculatata and zona reticularis
what happens when ACTH binds to its specific receptor?
Stimulation of adenylyl cyclase leading to increase production of cAMP.
what happens in G protein cascade caused by binding of ACTH to its receptor?
This activates the steroidogenic enzymes responsible for the synthesis and release of steroid hormones.
when are secretions of ACTH and cortisol max during the day?
morning
when are secretions of ACTH and cortisol min during the day?
evening
what factor is extremely important to circadian rhythms?
light
what may induce a significant increase in synthesis and release of CRH, ACTH, Cortisol?
stress stimulus
how can stress be advantageous when releasing cortisol?
it provides energy and amino acids through the breakdown of tissue proteins, especially under conditions where normal feeding is not feasible.
how can stress be disadvantageous when releasing cortisol?
it prevents wounds from healing
what can prolonged stress result in?
- elevated blood glucose
- adrenal diabetes
- decreased immune response
- loss of bone
what is addison’s disease a result of?
hypofunction of the adrenal glands
what is the main cause of addison’s disease?
- athrophy of adrenal gland due to TB
- may involve total destruction of the adrenal
what are the most severe symptoms of addison’s disease due to?
deficency of mineralocorticoids
what are some symptoms associated with addison’s disease?
- decreased ECF
- decreased plasma volume
- decreased cardiac output
- acidosis
- hyponatremia
what is hyponatremia?
low sodium levels in blood
what is cushing’s disease?
hyperfunction of the adrenal glands
what happens to the adrenal cortex in the case of cushing’s disease?
hyperplasia due to increased levels of ACTH
what happens in the case of cushing’s disease?
- excessive production of glucocorticoids
- increased production of mineralocorticoids
- uncontrolled sex hormone production leads to masculinization of female
what does an increased production of mineralocorticoids lead to?
alkalosis (increased blood pH)
where is the pancreas located?
behind the stomach
what part of the pancreas is endocrine?
islets of langerhans
what type of hormones are insulin and glucagon?
protein hormones
what is the main function of insulin?
reduces levels of glucose in the blood
what is the fasting glucose level?
80 mg/ 100 mL
how is glucose transported into cells?
through active transport
what is glucose converted to in the liver and muscles?
glycogen
what is glucose converted to in adipose tissue?
glucose is transformed to fat
what happens when B cells of the pancreas are destroyed?
leads to diabetes milletus where most tissues cannot take up glucose efficiently, thus it accumulates in circulation
can accumulation of glucose in circulation occur even without ingesting glucose?
yes, due to gluconeogenesis, proteins are broken down into aa and synthesis of glucose
under conditions of diabetes what happens to adipose tissue?
its broken down into FFA and used as the main source of energy, however not fully oxidized and leaves ketoacids and BHB which leads to ketosis
what are some symptoms associated with diabetes milletus?
- decreased blood pH (Acidosis)
- diabetic coma
- death
- glycosurea
- dehydration
- thirst
at what levels of blood glucose does it begin to spill in urine?
> 180mg/100mL
what is needed to restore levels of blood glucose to normal?
insulin injections
what is another name given to type 1 diabetes?
insulin dependent diabetes
what is another name given to type 2 diabetes?
insulin independent diabetes
what are possible causes for type 1 diabetes?
destruction of B cells or defective insulin release
treatments for type 1 diabetes?
insulin injections and proper diet
or
drugs which will stimulate release of insulin
is 20-30mg/100mL of glucose enough for the brain?
no
what type of diabetes is juvenile diabetes?
type 1 generally, however with increasing obesity, type 2 has become more prominent
how to detect type 2 diabetes?
insulin levels tend to be abnormally high
what causes for type 2 diabetes
hyperresponsiveness of target cells to insulin often due to decreased number of insulin receptors
how is type 2 diabetes related to obesity?
over eating causes for prolonged levels of high insulin down regulates the function of these receptors
how can a proper diet and exercise be a treatment for type 2 diabetes?
Decreased caloric intake = decreased insulin and thereby up regulation of receptors.
The # of insulin receptors is also increased in response to frequent endurance exercise
how is glucose tolerance in diabetes?
decreased
how is glucose tolerance in hyperinsulinismn
increased
how to conduct a glucose tolerance test?
- fasted levels are tested
- given 0.7-1.5g/KG BW of glucose
- test after 1h, 2-3H
how will the graph of a normal patient look like when testing glucose tolerance?
fasted around 80mg/100mL
after 1h: Spikes up to around 130 mg/100mL
after 2-3H: returns back to normal
how does the graph for glucose tolerance differ in a diabetic patient?
fasted glucose is more elevated, blood glucose will spike more and will take much longer to return to normal
what other test can be done to measure glucose tolerance?
AIC hemoglobin concentration, levels of A1C in blood indicate glucose levels
what do high A1C levels indicate?
shows that over past few week glucose levels have been elevated; may show a sign of lack of control
regulation of insulin secretion?
B cells respond to levels of blood glucose; low= decreased insulin secretion, high; increase insulin secretion
why does insulin begin to leave the pancreas even before the blood glucose levels increase
◦ The release of gastrin and vagal impulses in response to food stimulate the beta-cellsto induce insulin release.
what cell is responsible for the synthesis of glucagon?
a cells of the pancreas
what is the function of glucagon?
Raises blood sugar by promoting glycogenolysis (breakdown of glycogen) and gluconeogenesis (synthesis
of glucose) in the liver (it mimics glucocorticoids).
◦ Increases the rate of lipolysis in adipose tissue leading to increased concentration of FFA in the circulation.
what controls release of glucagon?
levels of blood glucose
high= decreased glucagon synthesis and release
low-= increased synthesis and release
why is glucagon not as important as insulin?
because blood glucose levels can be increased by other hormones such as cortisol and epinephrine
what type of hormone is GH?
polypetide
where is GH produced?
anterior pituitary
what is GH responsible for?
responsible for growth; increases protein synthesis, enhancing AA uptake and accelerates transcription and translation of mRNA, increases rate of lipoylsis
where are somatomedins produced?
in the liver under stimulation of GH
which one between GH can somatomedins can increase protein synthesis?
both
which one between GH can somatomedins can increase lipolysis?
GH only
which one between GH can somatomedins cans timulate growth?
only IGF-1 and IGF-2
what hormones are stucturally similar to insulin and are named IGF 1-2
Somatomedins
under what conditions may somatomedins bin to insulin receptors and vice versa?
under high concentrations
how is GH release controled?
through a complex feedback mechanism involving GRH and somatostatins
what are somatostatin?
they inhibit GH release
what happens if person is GH deficient?
decreased physical growth
what happens if person has excess GH ?
in youth: gigantism
adults: acromegaly