Endocrine Hormones Flashcards
Cell types of the pituitary gland:
Somatotropes release __________
Growth hormone
Cell types of the pituitary gland:
Corticotropes release ________
adrenocorticotropic hormone
Cell types of the pituitary gland:
Thyrotropes
Thyroid stimulating hormone
Cell types of the pituitary gland:
Gonadotropes release _______
Leuteninzing hormone, follicle stimulating hormone
Cell types of the pituitary gland:
Lactotropes release ______
prolactin
Hormones that come from the anterior pituitary gland
- Thyrotropin
- Growth hormone
- Corticotropin
- follicle stimulating
- luteinizing
- prolactin
What stimulates release of hormones from the posterior pituitary gland?
posterior: nerve signals that originate in the hypothalamus
What controls release of hormones from the anterior pituitary gland?
- hormones secreted within the hypothalamus called hypothalamic releasing and hypothalamic inhibitory hormones
- brought to the anterior pituitary through small blood vessels called the hypothalamic-hypophysial portal vessels
- the hormones act on the glandular cells to control their secretions
osmoreceptor
found in hypothalamus. Shrinks and expands depending on osmolarity of blood going by
Shrink = increased signals, increased ADH
Growth hormone physiologic effects
- promotes growth of many body tissues (increased size and number of cells)
- promotes protein synthesis
- increased use of fatty acid for energy
- decreased use of glucose
* GH enhances body protein, uses up fat stores, and conserves carbohydrates
What does Growth hormone need in order to have effect?
insulin
carbohydrates
*to provide the energy needed for the metabolism of growth and enhance transport of some amino acids into cells
How much does the amount of growth hormone change throughout the lifespan?
you will have 25% of what you had as an adolescent when you are elderly
What stimulates release of growth hormone?
- starvation (especially severe protein deficiency)
- hypoglycemia or low concentration of fatty acids in the blood
- exercise
- exciement
- trauma
- ghrelin (tells you you are hungry)
- increased during first 2 hours of deep sleep
GH regulation
- Controlled mostly by GHRH more than GHIH
- GHRH attaches to GCPR on the GH cells, activates adenylate cyclase, etc…increases Ca into cell and causes vesicle release
- also controlled by Gherlin and IGF-1
GH summary
What are the two major thyroid hormones and the percent which you find them in?
Thyroxine (T4)- 93%
Triiodothyronine (T3)- 7%
Which thyroid hormone is more potent?
Triiodothyronine is 4x as potent
it is present in smaller quantities and has a shorter DOA
What is thyroglobulin?
A vesicle containing thyroid hormones
Formation of a thyroid hormone
- Iodide enters cuboidal cell surrounding colloid.
- conversion of iodide to an oxidized form of iodine which can then combine directly with the amino acid tyrosine.
- Enzyme peroxidase makes oxidation happen faster
- over time the iodotyrosines become coupled with each other.
- This thyroxine remains in the thyroglobulin molecule
How is Thyroid hormone transported?
- upon enteing blood, more than 99% of T4 and T3 are bound to proteins
- thyroxine-binding globulin (mostly)
- thyroxine-binding prealbumin
- albumin
- this affinity for proteins acts as a reservoir for the thyroid hormones, releasing them slowly into the tissues
Thyroid hormone receptors:
- Attached to DNA or very close to them
- the thyroid hormone receptor forms a heterodimer with retinoid X receptor (RXR) at specific thyroid hormone response elements on the DNA
- This activates receptor and starts the transcription process
- Make a bunch of mRNA then RNA
- actions of thyroid hormones result from the functions of these new proteins
generally, what do thyroid hormones do?
increase the metabolic activities of almost all the tissues of the body
** number and size of mitochondria increase
How is thyroid hormone stimulated?
- hypothalamus secretes thyrotropin releasing hormone (TRH)
- this activates the anterior pituitary to secrete thyroid stimulating hormone (TSH)
- TSH increases all the known secretory activities of the thyroid glandular cells
- T4 and T3 (more T4) go to target organs
How is thyroid hormone negatively controlled?
Increased thyroid hormone in the body fluids decreases the secretion of TSH from the anterior pituitary
what does the medulla of the adrenal gland produce?
catecholamines
what does the cortex of the adrenal gland produce?
- 2 major types of hormones
- mineralcorticoids
- corticosteroids
- 1 minor type of hormone
- androgenic hormones
What are the three layers of the adrenal cortex?
And what do they each secrete?
- zona glomerulosa- thin cells just under capsule
- secrete aldosterone in response to extracellular ang II and K.
- zona fasciculata- middle and widest zone (75%)
- secretes glucocorticoids (cortisol and corticosterone
- secretes andrenal androgens
- secretion controlled by ACTH
- zona reticularis- inner zone
- secretes androgens
Actions of Aldosterone
- retains Na and excretes K into tubule in exchange
- causes secretion of H ions in exchange for Na in the intercalated cells of collecting ducts
- decreases the H concentration and causes metabolic alkalosis
what role do intercalated cells play?
alpha vs beta?
- they are involved with acid/base homeostasis
- alpha- secreces acid (H), reabsorbs HCO3
- beta- secretes HCO3, reabsorbs (H)
What do principle cells do?
- mediate Na/K balance in the collecting duct with Na/k channels in the cells membrane
Aldosterone pathway
- triggered by RAAS system when low circulating volume is sensed
- released directly when high K is sensed
- increases number of Na/K exchangers and Na/Cl symporters
- water follows Na
- fluid balance increases
What do thiazide diuretics antagonize?
anything that aldosterone does.
thiazide diuretics:
decrease Na/K channels
decrease Na/Cl symporter
water follows and is secreted
What does cortisol do?
- increases gluconeogenesis
- antagonizes insulin’s effects to inhibit gluconeogenesis
- increases protein mobilization
- increases fat mobilization
- removes the GLUT4 from cell membranes, causing insulin resistance
- suppresses immune system
What percentage of cortisol binds to plasma proteins?
How long is the half life?
90-95%
has a long half life 60-90 minutes
How much circulating aldosterone is bound to proteins?
What is the half life?
60%
shorter half life of 20minutes
what is the normal plasma and ISF concentration of ionized Ca?
What is the ionized Ca used for?
1.2 mmol/L
50%
Used for most important functions
What is the concentration of bound Ca in plasma and ISF?
How is this Ca used?
1 mmol/L
the Ca bound to proteins is used as a reservoir/backup supply
What do you need/needs to function to be able to absorb Ca?
Vitamin D
liver function, kidney function
What stimulates the secretion of parathyroid hormone?
Where is it released from?
decreased blood calcium
