Flashcards in Endocrine Physiology Deck (59)
Where is the preprohormones for protein and peptide hormones first synthesized?
Rough endoplasmic reticulum.
signal peptides are cleaved from preprohormone producing prohormone which is transported to the golgi aparatus.
What are amine hormones?
These are derivatives of tyrosine so mostly thyroid hormones, epinephrine, and norepinephrine.
Give an example of a hormone that functions through positive feedback.
Positive feedback is very rare.
LH reacting to estrogen release is an example.
As Estrogen is released before ovulation, it acts on the anterior pituitary to release LH. LH acts on the ovaries and increases estrogen release even more.
What do TSH, LH, and FSH all hav in common?
These all share the exact same alpha subunit however have different beta subunits.
It is important to understand that Beta subunit is the important portion.
What is the importance of POMC?
This is broke apart to form ACTH as well as melanocytre stimulating hormone.
Growth hormone is directly identical with what hormone?
What effect does growth hormone have on glucose?
Decreases glucose uptake into cells.
What is octreotide?
A somatostatin analogue that treats excessive growth hormone release.
What is the difference between acromegally and gigantism?
Acromegally occurs in adults.
gigantism occurs in children.
How is prolactin controlled?
Thyroid releasing hormine from the hypothalamus increases Prolactin secretion.
Dopamine released from the hypothalamus decreases the secretion of prolactin.
Prolactin also negatively regulates itself by causing dopamine release.
What is bromocriptine?
A dopamine analogue that can be used to inhibit prolactin overgrowth.
What are the two hormones released from the posterior pituitary?
Oxytocin and ADH
Describe ADH's effect on V1 cells vs V2 cells
Vi effects are contriction of vascular smooth muscle.
V2 effects are increased H2O permeability in the principal cells
What does oxytocin do?
Released from the periventricular nuclei of the posterior pituitary, it results in ejection of milk from the breast following suckling.
How does the dexamethasone suppresion test work?
Normally dexamethasone would stop ACTH secretion and subsequently cortisone release.
With ACTH-secreting tumors, low does dexamethasone does not inhibit cortisol secretion but high does does.
In people with adrenal cortical tumors, neither high or low dose dexamethasone inhibits cortisol secretion.
How do glucocorticoids (cortisol) exhibit antiinflammatory effects?
By inducing the synthesis if lipocortin which is an inhibitor of phospholipase A2.
Inhibits the release if IL-2 (recruits T cells)
Inhibit the release of histamine and serotonin from mast cells and platelets.
How does cortisol elevate blood pressure?
Up regulates alpha 1 receptors on arterioles increasing sensitivity to norepinephrine.
Why is there hyperpigmentation in adrenocortical deficiency?
Lack of cortisol leads to excessive ACTH release.
ACTH has a pigmentation effect.
How does glucose stimulate insulin release from beta cells?
Binds to Glut 2 receptors.
Glucose is formed into ATP closing the potassium channels leading to depolarization and calcium channels opening releasing insulin and C-peptide.
What effect does CCK and amino acids have on glucagon release?
Increase glucagon release.
How does magnesium interact with PTH?
Decreased magnesium can cause an increase in PTH.
Severe decreases in magnesium actually cause a deficiency in PTH.
Increased hyroxyproline excretion is a sign of .....
Increased bone reabsorption seen most commonly through PTH activity.
In children vitamin D deficiency causes.... In adults it causes?
In children it causes rickets
In adults it causes osteomalacia.
whats the active form of vitamin D?
Made in the kidneys by 1 alpha hydroxylase.
Liver makes 25-OH cholecalciferol which is the preform f 1,25 activated in the liver.
The sertoli cells are responsible for....
Forming anti-mullerian hormone in men
and spermatogeisis folowing FSH.
The leydig cells are responsible for forming....
Form testosterone in men following LH reaction. .
5 alpha reductase
converts testosterone to its active form dihydrotestosterone in the prostate.
Where can Glut 1 be found?
Found within the brain and cornea
Where can glut 2 be found?
Beta islet cells
These are bidirrectional.
Where can glut 3 be found?
Found within the brain
Where can GLUT 5 be found?
Found within the spermatocytes, and GI tract.
THIS TRANSFERS FRUCTOSE.
Which organs can take up glucose without the need for insulin?
Brain, RBC, Intestine, Cornea, Kidney, Liver.
What effect does GH have on insulin?
Increases insulin resistance thus increasing insulin release!
Think about the need to grow!
Which hormone does dopamine negatively inhibit?
Negatively inhibits prolactin release.
Thus Dopamine antagonists such as antipsychotics can cause increased prolactin levels!
which hormones are down regulated by somatostatin?
Octreotide is an anologue used to treat acromegally.
what hormone increases prolactin release?
Stimulates hunger and GH release
Increased in prader-willi syndrome
Satiety hormone produced by adipose tissue
Describe V1 and V2 ADH receptors
V1 works on the blood pressure (think of alpha1)
V2 works on the kidneys to increase water absorption in the principle cells of the collectin duct
What's the difference between central and peripheral diabetes insipidus
Central are within the kidneys through V2 receptors. This is called nephrogenic diabetes insipidus.
Peripheral are problems with the central release of ADH.
ADH analog which is a treatment for central diabetes insipidus.
(ADH cannot be released by the posterior pituitary)
If 17 alpha hydroxylase is knocked out, what builds up?
Cortisol and sex hormones are knocked out.
There is excessive aldosterone formation.
If 21-hydroxylase is knocked out, what builds up?
Both Cortisol and Aldosterone are knocked out.
Sex hormones greatly elevate.
If 11beta-hydroxylase is knocked out, what builds up?
Aldosterone and cortisol are knocked out
Sec hormones greatly increase..
How does cortisol feedback on itself?
Cortisol works to feedback on itself through the release of ACTH in the hypothalamus.
Excess cortisol decreases ACTH release.
Vitamin D actions
Increase calcium and phosphate reabsorption by the gut.
Increase calcium reabsorption from the bone.
What is the feedback for vitamin D?
increased PTH causes increased vitamin D as well as decreased calcium and phosphate levels.
High levels of 1,25 OH inhibits vitamin D production.
Which cell types release parathyroid hormone?
Chief cells in the parathyroid gland.
which enzyme in the kidney activates vitamin D?
1alpha-hydroxylase in the proximal convuluted tubule.
Activated by PTH
Which type of PTH release can actually stimulate bone formation?
Intermittent PTH release can stimulate bone formation.
What cell type releases calcitonin and how does it work?
Calcitonin is released by parafollicular cells in the thyroid.
Decreases bone resoprtion and is activated by high levels of serum calcium.
What channel types are insulina nd growth factors
What receptor types are vitamin D?
Steroid intranuclear receptor.
What happens if there is increased sex hormone binding globulin in men?
Testosterone is greatly decreased
Can lead to gynecomastia
In women a decrease in sex hormone binding globulin can cause
During pregnancy there is increases SHBG.
How does sex hormone binding globulin change with pregnancy?
It is increased thus free estrogen levels remain unchainged.
Peroxidase for thyroid
organifies iodine into MIT and DIT
5'-deiodinase for thyroid
This hormone converts T4 to T3