definition
hormone
chemical messengers produced by endocrine glands
hormones are produced by
endocrine glands
endocrine glands
ductless
hormones are released
into circulation and travel to target tissues where after binding to specific receptors
they exert specific effect
endocrine glands
definition
no ducts
- -release hormones into tissue fluids
- -have dense capillary networks to distribute hormones
- -intracellular effects, alter target cell metabolism
Exocrine glands
definition
- -ducts carry secretion to a surface or organ cavity
- -extracellular effects (food digestion)
steroids
–all steroids are metabolites of cholesterol
steroids are
hydrophobic
most steroid hormones have
specific binding protein in the plasma
e.g. SSBG, transcortin
Steroids bind
specific nuclear receptors
example of progestins
progesterone
progesterone
main sex steroid in the second half of the menstrual cycle
and pregnancy
progesterone maintains
pregnancy
mineralocorticoids
aldosterone
Na+ retention
glucocorticoids
cortisol
INCREASE glucose
dihydroxy Vit D
calcitriol
not a steroid
acts as nuclear receptor Ca2+ absorbed
androgens
testosterone
main circulating male sex steroid
penis growth, 2nd sex char, male behavior, libido
testosterone converted in target cells to
estradiol
or
5 alpha dihydrotestisterone
deficiency of
estradiol
or
5 alpha dihydrotestisterone
born with ambiguous genitalia
despite XY
possible sex reveral at puberty
male born with few/no androgen receptors
estrogen
18C
estradiol
estriol
estradiol
menstrual cycle
estriol
late in pregnancy
uterus growth
secondary sex characteristics
female behavior, libido
protein and polypeptide hormones
have primary amino acid structure
polypeptide hormones
have less amino acids than protein hormones
examples of protein hormones
- insulin
- growth hormone
- follicle-stimulation hormone
- glycoproteins
glycoproteins
LH
FSH
TSH
peptide hormone…
anti-diuretic hormone
oxytocin
GnRH
for each receptor sites on plasma membranes..
hormone binds and leads to a cascade of events in cell and ultimately an effect
amine hormones
have NH2 group at end of molecule synthesized from single amino-acids
amine hormones act
at plasma membrane receptor
e.g catecholamines
amine hormones ex
- norepinephrine
- epinephrine
- melatonin
eicosanoids
prostaglandins
hypersecretion
endocrine secretion
Too much
hyposecretion
endocrine secretion
too little
endocrine diseases
- hypersecretion
- absence/ nonfunctioning receptors
- hyposecretion
endocrine organs
- pineal gland
- hypothalamus
- pituitary gland
- thyroid gland
- thymus
- adrenal gland
- parathyroid gland
- gonads
pineal gland
found in the brain
pituitary gland
hypophysis
pituitary gland is suspended
from hypothalamus by stalk (infundibulum)
location and size of pituitary gland
housed in sella turcica of sphenoid bone
1.3 cm diameter
adenohypophysis
anterior pituitary
arises from hypophyseal pouch
hypophyseal pouch
out growth of pharynx
neurohypophysis
arises from brain
pituitary gland sits
in hole called sella turcica
turkish saddle
pituitary gland is called
“master gland”
of endocrine system
anterior pituitary
- TSH
- ACTH
- LH
- FSH
- GH
- prolactin
posterior pituitary
- oxytocin
2. vassopressin
target gonads
gonadotropin
FSH
follicle stimulating hormone
LH
luteinizing hormone
TSH
thyroid stimulating hormone
thyrotropin
ACTCH
adrenocorticotropic hormone
corticotropin
PRL
prolactin
GH
growth hormone
somatotropin
pars intermedia
–present in fetus, absent in adult
–remnant cells
–produce MSH
Remnant cells
produce POMC
(pro-opiomelanocortin)
processed into ACTH and endorphins
MSH in animals influences
pigmentation of skin, hair, or feathers
MSH
no present/functioning in human pituitary but present in skin
hypothalamus
“master gland”
neuroendocrine organ
hypothalamus synthesizes
OT
ADH
hypothalamus controls
the release of hormones at the anterior pituitary gland
hypothalamus secretes
releasing factors or inhibiting factors
blood goes to
anterior pituitary from hypothalamus
thyroid
found on either side of trachea
thyroid hormones produced by
thyroid epithelial cells from thyroglobulin
thyroid hormones
T4 T3
increases BMR
Increases cell oxidation
Increases heat generation (uncoupling)
growth and development
thyroid produces…
calcitonin by C cells
Decreases Ca2+ in bloodstream
parathyroid glands
found embedded in the thyroid tissue
parathyroid glands produce
parathyroid hormone
- -polypeptide
- -increase Ca2+ in bloodstream
thymus
produces thymosins and other hormones
Atria produce
atrial natriuretic factor or peptide
ANF or ANP
ventricles brain
natiuretic factor
or peptide
BNF or BNP
Na+ balance in body..
indirectly BP regulation
adrenal glands found
superior to the kidneys in most mammalian species
involved with stress response
adrenal cortex
outer layer
responsible for the synthesis of
- aldosterone
- cortisol
- sex steroids
adrenal medulla
inner layer
responsible for secretion of
epinephrine
norepinephrine
involved in emergency reactions
stomach
releases gastrin from G-cells
duodenum releases
cholecystokinin (CCK)
duodenum goes
to gallbladder to release bile
duodenum goes to pancreas
to release enzymes to break down protein
duodenum releases secretin
goes to pancreas to release HCO3- to neutralize low pH
pancreas releases
insulin
glucagon
somatostatin
pancreatic polypeptide
fat cells
leptin
kidney
Renin
erythropoietin
gonads
ovaries
testes
ovaries produce
estrogen (estradiol)
progesterone
inhibin
relaxin
testes produce
testosterone
inhibin
placenta
rich source of hormones
human chorionic gonadotropin
hCG
maintains pregnancy
acts like LH-basis for home pregnancy test
human placental lactogen
HPL
acts like growth hormone
progesterone
maintains pregnancy
estrogen
estriol
feeback mechanisms
regulate hormone concentrations
negative feedback loop
LH
LH to blood
- causes testosterone production INCREASE
- testosterone enters the blood (brain): inhibits release of LH DECREASE
positive feedback loop
very few hormonal systems exist
hypothalamus is critical
to life controlling reproduction, body temp, stress response, eating, drinking
pituitary gland
made up of anterior/posterior
adrenocorticotropic hormone
ACTH
produced from proopiomelatocortin(POCMC)
released into blood –> adrenal cortex –> release glucocorticoids
cortisol is major INCREASE
-tropin
exerting an action or stimulating growth
glucocorticoids exert
a negative feedback effect on
ACTH release at the anterior pituitary
Luteinizing hormone
LH
glycoprotein to blood
LH action on females
causes produces ovulation
stimulates CL to produce progesterone (maintain pregnancy) and estrogen
LH action on
males
stimulates Leydig or intestitial cells in testis –> testosterone INCREASES leads to male characteristics
beard, body hair, muscling, balding
testosterone or progesterone exert
a negative feedback
luteinizing
causes formation of the corpus luteum CL
Follicle-stimulating hormone
FSH
glycoprotein
2nd gonadotropin
FSH…
ACTIONS on gonads
female STIMULATES FOLLICLES
causes estrogen release (by FOLLICLES in ovaries)
stimulates production of inhibin which inhibits FSH release
FSH males stimulates
spermatogenesis
Thyroid stimulating hormone
TSH
Thyrotropin
TSH
glycoprotein
acts on thyroid gland
- -production and release of thyroid hormones
- -growth
–thyroxine and triiodothyronine INCREASE
thyroid hormones have
negative feedback effct on the TSH
growth hormone
GH
protein
called somatotropin
muscle size INCREASE and bone accretion
GH acts
through IGF-1 on growth
excess growth hormone
in children leads to gigantism
excess GH in adults
acromegaly
only affects areas that can still grown
hands, head, feat
deficiency of GH
hypopituitary dwarf
treated with human growth hormone
laron dwarf
lacking GH receptor
prolactin
protein
lactation
- -mammary gland development
- -milk production
melanocytes
cells in skin that contain melanin changes skin color
brown/black pigment
eumelanin
red/orange
pheomelanin
hormones released from the posterior pituitary
produced in hypothalamus
neurosecretory neurons
nerve cell bodies in the hypothalamus.
modified axons to PP
neurosecretory neurons end up with
neurosecretory terminals
ADH or vasopressin
9 amino acids
ADH or vasopressin
acts on
distal convoluted tubule and collectind ducts
ADH vasopressin
does what
INCREASE permeability to H2O
no feedback mechanism
oxytocin
size
9 amino acid
peptide
Oxytocin…
pitocin is a sythetic oxytocin analog
Oxytocin actions
INCREASE smooth muscle contraction in
uterus, vagina, mammary glands
Milk ejection
Hypo –> PP –> oxytocin –> milk ejection
Milk production
Hypo –> AP –> prolactin –> milk production
thyrotropin releasing hormone
TRH
released by hypothalamic neurons into blood
TSH secretion INCREASED
negative feedback
prolactin secretion INCREASE