Hormones Flashcards
What are hormones?
chemical messengers that are secreted by endocrine glands in the bloodstream and that can produce specific responses when reaching a target organ
What type of hormones are there based on chemical structure?
- peptide/protein
- steroids
- amino acid derivative/amine
What are the characteristics of peptide/protein hormones?
- synthesised as pro hormones
- secondary messengers
- mostly water soluble
- fast changes in protein activity
- LH, FSH, GH, insulin etc.
What are the characteristics of steroid hormones?
- synthesised from cholesterol
- lipid soluble
- primary messengers
- slower onset, longer duration
- Cortisol, estrogen, testosterone, etc.
What are the characteristics of amino acid derivative/amine hormones?
- synthesised from amino acid tyrosone or tryptophan
- mix of water and lipid soluble
- mix primary and secondary messengers
- adrenaline functions like peptides, thyroid hormones function like steroids.
- catecholamines(adrenaline and noradrenaline), thyroxine etc.
What is the difference between primary and secondary messengers?
primary messengers go all the way to the nucleus to activate protein synthesis by itself
secondary messengers activate a cascade in the cytoplasm to activate protein synthesis, it does not go into the cell itself
What are the types of hormones based on functional effects?
- autocrine (targets itself)
- signalling across gap junctions
- paracrine (targets nearby cells)
- endocrine (targets distant cells through the blood streams)
What is the pathway and production of TH t3 and t4?
- hypothalamus gets stimulated by decreased TH, cold weather, hypoglycemia etc.
- Releases TRH in the hypothalamo-hypophyseal portal system
- Anterior pituitary releases TSH
- TSH stimulates thyroid gland to release TH in blood
- TH acts on cell and inhibits hypothalamus
Does testosterone work in a paracrine or endocrine manner?
BOTH! paracrine > leydig cells to stimulate spermatogenesis and endocrine to stimulate muscle growth
What is the pathway and production of GH?
- hypothalamus gets stimulated to release GHRH by age, time of day, stress and exercise etc.
- Releases GHRH in hypothalamo-hypophyseal portal system
- Anterior pituitary releases GH
- GH stimulates hepatocytes to relase IGF’s in the blood
- Both GH and IGF’s stimulate target cell effectors and inhibit hypothalamus
What is the target of testosterone?
- liver tissue > increase glycogenolysis
- lungs
- heart
- bone (stimulate osteoblast activity and chondrocyte maturation)
- skeletal muscle
- sertoli cells
what is hyperthyroidism?
the thyroid glands make too much TH, causing weight loss, hand tremors, and irregular heartbeat
What effects does IGF1 have?
- increase AA uptake and protein synthesis in muscles
- increase osteoblast and osteoclast activity, collagen type I and proteoglycans
- stimulates proliferation/differentiation of chrondroblasts (interstitial growth) in cartilage
What effects does GH have?
- increases gluconeogenesis and IGF1 production in liver
- stimulates lipolysis in adipose
- stimulates increased amino acid uptake in muscle
What is adrenarche?
activation of adrenal glands
what is pubarche
appearance of pubic arche
what is menarche
first menstrual bleeding
what is thelarche
appearance of breast tissue
from the anterior pituitary gland, what hormone is released to stimulate leydig cells to make testosterone
LH
from the anterior pituitary glandm what hormone is released to stimulate sertoli cells to up spermatogenesis?
FSH
What starts puberty?
growth peptide, nitric oxide etc. in the hypothalamus stimulates the GnRH pulse generator, meaning the pulse for GnRH gets higher and puberty is set in motions.
What are factors that stimulate the GnRH neuron?
- Kisspeptin
- neurokinin B
- GABA
- MKRN3
- neuroexcitatory amino acids
what is juvenile pause?
months and years after birth: decrease in activity of the hypothalamic- pituitary gonadal axis.
What are the 3 phases in the menstrual cycle?
- menses
- proliferative phase (estradiol and LH peaks)
- secretory phase (progesteron peaks)
What is the follicular phase?
Eggs begin to develop and one matures completely. after menstruation until 14 days
What happens in the luteal phase?
Corpus luteum is formed happens after 14 days untill menstruation
What is the process of the growth hormone(process to production)
- hypothalamus get stimulated to release GHRH by time of day, age, stress and exercise, nutrient levels in the blood
- release GHRH in hypothalamus-hypophyseal portal system
- anterior pituitary releases GH
- GH stimulates hepatocytes to release IGF’s in liver into the blood
- both GH and IGF’s stimulate target cell effectors and inhibit the first step again
What hormones/molecules can growth be affected by?
- glucocorticoid, inhibitory effect on the growth plate
- insulin, deficiency blocks growth, hyperinsulimia stimulates excessive growth
