Transcript Endocrine Part 2 Powerpoint

Endocrine System Part 2
Thyroid
• The thyroid is a gland in your
neck, stimulated by the anterior
pituitary’s release of TSH
• The thyroid releases thyroxine
which stimulates cells to increase
metabolism
• Thyroxine’s key ingredient is
iodine, which is required in small
doses for life
– Hypothyroidism (less thyroxine)
causes exhaustion and weight gain
– Lack of iodine can cause
hypothyroidism and a swelling of
the thyroid (goiter)
Protip: do NOT OD on iodine
• Common reaction to discovery of
metabolic properties of iodine:
“Wow awesome I can take iodine
and it will make me burn more
calories!”
– Yes, but…
• Excessive intake of iodine can result
in a thyroid storm, where all the
internal organs are also in overdrive
– Diet-based hyperthyroidism
– Results in severe illness and possible
death (and yes, weight loss)
Calcium Management
• The thyroid releases calcitonin,
ostensibly to decrease calcium
levels
– Not clear whether its action is
important
• The thyroid also has small
glands attached called the
parathyroid glands
– Four or eight small dots on the
back
• The parathyroid glands release
parathyroid hormone or PTH
PTH
• PTH is released when blood
calcium is low
– Stimulates digestive system to
absorb calcium
– Stimulates kidneys to reabsorb
calcium from urine
– Stimulates osteoclasts to release
calcium from bone
• This is a big part of why
calcium intake should be
ongoing and not just once a
week
Glucose Management
• Long-term metabolism is
controlled by the pituitary
gland (GH)
• Medium-term metabolism is
controlled by the thyroid
(thyroxine)
• Short-term metabolism is
controlled by the pancreas
– Releases hormones that
manage glucose levels in the
blood
Why Glucose?
• Recall that glucose is the
energy source for all cells in
the body
– Neurons in particular
absolutely must be nourished
by glucose
• Also recall that glucose is a
polar (hydrophilic) molecule
and so is “sticky”
– No one wants to have their
heart pump syrup through their
arteries
Insulin
• The pancreas releases insulin
whenever blood glucose gets high
– Signals all cells to absorb additional
glucose
• This helps cells use and store
energy
– The liver produces more glycogen
– Fat cells convert sugar to fat
• If cells cannot absorb sugar then
they cannot produce ATP and make
things/move things
– What do we call it when there is not
an insulin signal to the cell?
Insulin and Diabetes
• Failure to release or receive
insulin is called diabetes
- Excessive sugar in the blood is
called hyperglycemia and often
results from diabetes
• Type I diabetes results from a lack
of insulin (usually damage to the
pancreas by the immune system)
• Type II diabetes results from
excessive sugar intake, where
cells become resistant to insulin
signals via overuse
Glucagon
• The pancreas releases
glucagon whenever blood
sugar gets low
– Stimulates fat and liver to
release glucose into
bloodstream
• A deficiency of glucagon or
excess of insulin can cause
hypoglycemia
– Critically low blood sugar causes
crankiness followed by coma
and death
Gonads
• The testes in men and ovaries in
women are collectively referred
to as gonads
– AKA “the ‘nads”
– Produce gametes (sperm & eggs)
for babymaking
• Produce sex hormones
testosterone, estrogen and
progesterone
– Stimulated to do so by FSH and LH
from the anterior pituitary
Effects of Sex Hormones
• Sex hormones promote production of
gametes and development of gonads
• Sex hormones also promote secondary
sexual characteristics, especially after
puberty
– Men: facial/chest hair, Adam’s apple
– Women: Breast development, wider hips
– Men and women: pubic and axillary hair,
production of sebum, actual interest in sex
• What part of the brain do you think the sex
hormones affect?
Bonus Hormones
• Erythropoietin (EPO) is a hormone released by
the kidneys in response to low blood oxygen
– Increases production of red blood cells
• Two hunger hormones act against each other:
– Leptin is produced by fat cells and lowers hunger
– Ghrelin is produced by the intestines that
stimulates hunger (mimicked by marijuana)
• Human Chorionic Gonadotropin (hCG):
Pregnancy hormone produced by the placenta
that blocks menstruation
– Tested for in pregnancy test
Negative Feedback Loops!
• Body temperature falls: TSH increased, thyroxine
increased, body temperature increases, TSH inhibited
• Glucose goes high: insulin released, glucose goes
down, insulin inhibited
• Glucose goes down: glucagon released, glucose goes
up, glucagon inhibited
• Calcium goes down: PTH released, calcium goes up,
PTH inhibited
• Also note that injecting steroids into the body will
register as testosterone levels, causing an excess to
cause the testes to shrivel in response