Endocrine System
for copying
Endocrine vs nervous
system
• act together to coordinate body’s activities
• both:
– use chemical messengers to communicate
cell to cell
– major function: homeostasis
• endocrine: slower response time
– hormones transported thru circulatory
system
– target cells (any cell with hormone receptor)
anywhere in body
• nervous: quicker conduction of signals
– neurotransmitters
– act on cells close by
Glands
• no ducts
• secretions released
and diffuse into
blood capillaries
• have ducts
• secretions released
onto surface
• example: sweat
glands, salivary
glands
Endocrine
Exocrine
2 types of hormones
• bind to protein
receptors in cell
membranes (do not
enter cell)
• receptor-hormone
activate enzyme in
cytoplasm  series
of reactions result in
cell response
• enter cell & bind to
receptor in
cytoplasm or nucleus
• Activates
transcription of gene
 protein produced
• generally action
slower than peptide
hormone
Peptide
Steroid
Endocrine system
hypothalamus
• part of brain
• secretes “releasing”
hormones that act on
pituitary gland
• axons that store the
2 posterior pituitary
hormones end there
Pituitary gland
• 2 lobes: posterior &
anterior
Negative Feedback Inhibition
Thyroid Gland
• stimulated by TSH
• secretes thyroxin (T4) and
triiodothyronine (T3)
– (-) feedback inhibition
• both have similar effects on target
cells
hypothyroidism
• Thyroid produces too little hormone
• several causes: Hashimoto’s autoimmune/
lack of Iodine in diet  goiter (enlargement
of thyroid due to increased TSH
stimulation
• Symptoms:
– Adults: lethargy, weight gain, anovulatory
cycles
– Infants:cretinism: dwarfism, low IQ, failure to
reach sexual maturity
hyperthyroidism
• excessive secretion of thyroid hormones
Parathyroid Glands
• 4 small glands embedded in posterior
surface of thyroid gland
• secrete: parathyroid hormone (PTH)
– regulated by serum Ca++ levels
• actions:
1. stimulates removal of Ca++ from bone
2. increases kidney tubules reabsorption of
Ca++
3. activates vit D which enhances Ca++
absorption from food
thymus
• upper thorax, posterior
to sternum
• largest in infants,
decreases as we age
• produces: thymosin –
programs T cells
Adrenal Cortex
• outer layer
• produces 2 kinds of steroid hormones
1. Glucocorticoids
–
–
major 1 – cortisol:
reduces swelling by inhibiting immune
system/ raises serum glucose (stimulates liver
to make glucose from proteins or lipids
2. Mineralocorticoids
–
–
major 1- aldosterone
acts on kidney to promote absorption of Na+ &
excretion of K+
pancreas
1. Insulin
–
–
–
protein
reduces blood glucose by increasing entry of
glucose into cells/making glycogen in
hepatocytes
regulated by blood glucose levels
2. Glucagon
–
–
–
protein
raises blood glucose by acting on glycogen
stores in liver
regulated by blood glucose levels
testes
• paired oval organs suspended in scrotum
• site of:
spermatogenesis
production of androgens:
Testosterone major one
made by interstitial cells/stimulated by FSH &
LH
– produces male 2◦ sex characteristics in puberty
– promotes growth & maturation of reproductive
system organs
– increases libido
–
–
1.
–
ovaries
• paired, almond-shaped organs in
pelvic cavity
• produce ova
• release: estrogens & progesterone
• begin functioning in puberty in
response to anterior pituitary
gonadotrophins
estrogens
• Estrone &Estradiol made by follicle
where ova is maturing
• stimulate:
– development of 2◦ sex characteristics
• work with progesterone to prepare
uterine lining for implantation
• help maintain pregnancy & prepare
breasts to lactate(those estrogens made
in placenta)
progesterone
• made &secreted by corpus luteum
• acts with estrogen to prepare uterine
lining for implantation
• quiets uterine muscle during early
pregnancy
• helps prepare breasts for lactation
placenta
• produces hCG (human Chorionic
Gonadotropin)
– stimulates corpus luteum of ovary to
continue producing estrogens and
progesterone so lining of uterus does not
slough off (like in menstruation)
– turns pregnancy tests +
– by 3rd mo pregnancy placenta produces
estrogen & progesterone (ovaries become
inactive rest of pregnancy)
– also produces hPL (human placental
lactogen) works w/E & P in preparing
breasts for lactation
Pituitary disorders
• Giantism:
• hypersecretion hCG
during chidhood
• abnl increse in
length of long bones
• hypersecretion hCG
in adulthood 
acromegaly
(epiphyseal plates
sealed) see
thickening of bones
of hands, face &
thickening of skin
on brow
• Diabetes
Insipidus:
• defects in ADH
• excrete large
volumes of urine
 dehydration &
thirst (bed-wetting
in children)
• can die w/in 2 days
from the
dehydration
Anterior
Pituitary
Posterior
Pituitary
Thyroid gland disorders
• Hypothyroidism:
• Cretinism: congenital
hypothyroidism
– severe mental retardation if not tx’d
– most states require testing new borns
• Myxedema:adults
– hallmark:edema of facial tissues, slow
HR, low body temp, sensitivity to cold,
dry skin & hair, muscle weakness
Thyroid gland disorders
Graves Disease
most common form of hypothyroidism
7 – 10 x more common in females
autoimmune disorder: autoantibodies
that mimic TSH  causes thyroid to
grow & make thyroid hormones
• signs: enlarged thyroid, exophthalmos
• tx: surgical excision of all or part of
thyroid or use of antithyroid drugs to
block synthesis of hormones
•
•
•
•
goiter
• enlarged thyroid
• could be associated with hypo- or
hyperthyroidism, or euthyroidism
(normal level of hormones) seen
when intake of iodine too low
Adrenal Gland disorders
• Cushing’s Syndrome:
• hypersecretion of cortisol
• caused by tumors that secrete
– cortisol (in adrenal cortex)
– ACTH  stimulates more cortisol
production in adrenal cortex
• muscle wasting  spindly arms & legs,
“moon” face, “buffalo hump” red face
• ~80% have hypertension
Adrenal gland disorders
• Addison’s Disease:
• hyposecretion of glucocorticoids &
aldosterone
• most are autoimmune: antibodies
cause adrenal cortex destruction or
block binding of ACTH to its receptors
• TB can destroy adrenal cortex
• symptoms: (after 90% of cortex
destroyed) mental lethargy, anorexia,
N/V, wt loss, hypotension,
hypoglycemia, muscular weakness
Pancreatic islet disorders
Diabetes mellitus: (honey-sweetened)
inabillity to use or produce insulin
4th leading cause death in USA
blood glucose levels high 
glucosuria
• 3 polys: polyuria, polydipsia,
polyphagia
•
•
•
•
Diabetes Mellitus
• Type 1: autoimmune abys destroy beta
cells
– mostly develops <20 yrs old
– most common in northern European
heritage
– cells starved for glucose so switch to
breaking down fatty acids  ketone
production  ketoacidosis  untx’d 
death
– transport of lipids from adipocytes 
plaque formation in walls of arteries =
atherosclerosis
– excess glucose attaches to proteins in lens
 catarracts
– small vessel disease: blindness, kidney
failure, amputation of toes  legs,
impotence
Diabetes Mellitus Treatment
• self-monitoring of blood glucose
levels  injections of insulin
• Diet:
– 45 – 50% carbohydrates
– <30% fats
Exercise
Type 2 Diabetes
• non-insulin-dependent diabetes
(NIDDM)
• more common (90% of all cases)
• typically occurs in obese people >
35 yrs old
– #s children diagnosed increasing
• many control it with diet,
exercise, wt loss
• oral hypoglycemic drugs
– stimulates secretion of insulin from
beta cells