Hormones affecting metabolism
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Transcript of Hormones affecting metabolism
Part 3: Metabolism Regulation
Endocrine System
Thyroid Gland
Location: base of neckventral surface of tracheaBelow & anterior to larynx
One of the largest endocrine glands in the body
Functional Unit: Follicle
Thyroid Gland
Structure:Two lobes4 cm long, 1-2 cm
wideconnected by a
narrow neck (isthmus)
Color: Red / BrownProduces thyroid
hormones
Thyroid Hormones: T3 and T4T4: Thyroxine / Tetraiodothyronine T3: TriiodothyronineRequires iodination
Comparing T3 and T4
T3 (Triiodothyronine) T4 (Thyroxine)
# of Iodine atoms 3 4
% in blood 0.3% 0.03%% produced by thyroid glands ~ 20% ~ 80%
Potency 4X more than T4 Not very
Half Life Span Shorter (1-2.5 d) Longer (5-7 d)
Main Purpose Regulate basal metabolic processes Conversion to T3
Questions
Why is more T4 made than T3?Why have T4 at all when T3 is so
much more effective?
Thyroid Hormones PropertiesPeptide hormone
Derived from the amino acid tyrosineNot very soluble in bloodHydrophobic and will diffuse into cells
Thyroid hormone receptorIntracellular, in nucleusHas greater affinity for T3 than T4
Thyroid Hormones FunctionAct on nearly every cell in the bodyRegulates metabolism
Increase glucose metabolism Increase protein synthesis Increase oxygen consumption (blood pressure,
heart rate)Regulates growth and tissue differentiation
DigestionReproductionBone growthMuscle toneDevelopment of nerve cells
Thyroid Regulation
Stimulus: change in metabolic rate (decreased metabolism)
Detected by hypothalamus
http://eso-cdn.bestpractice.bmj.com/best-practice/images/bp/en-gb/1121-2-iline_default.gif
Thyroid Regulation:Neuroendocrine pathway
Location HormoneHypothalamus
TSH Releasing Hormone / Thyrotropin releasing hormone (TRH)
Anterior Pituitary
Thyroid Stimulating Hormone (TSH)
Thyroid gland Thyroid hormones T3 & T4
Thyroid Regulation: FeedbackHigh levels of
T3/T4 in blood turn off production of TRH and TSH
http://yaplog.jp/cv/miharu_akimoto/img/21/img20090310_1_p.jpg
decreased metabolismIncreased blood sugar
Anterior pituitary release TSH
Hypothalamus release TRH
increase sugar metabolism
Thyroid Regulation
Thyroid gland released T3/T4
Thyroid Regulation: Feedback
Stimulus Low T3/T4 High T3/T4
Effect on TRH Stimulated Inhibited
Effect on TSH Increase InhibitedEffect on T3/T4 Increase Decrease
Thyroid Disorders
HyperthyroidismPlummer’s diseaseGrave’s disease
HypothyroidismHashimoto’s thyroiditis
Hyperthyroidism: Goiter
enlarged thyroid gland due to overactivity
Cause: Iodine deficiency
Low iodine levels means low levels of T3/T4
Body tries to compensate by working the thyroid gland more to make more T3/T4
Hyperthyroidism Symptomshigh T4 (thyroxine) releasehigh glucose metabolism:
weight loss with increased appetiteanxietyincreased heat release
Cause: Nodules(Plummer’s Disease)Nodule: small lumpstoxic multinodular goiter (many
nodules)
http://www.phoenity.com/diseases/goiter.html
Cause: Autoimmunity (Grave’s Disease)Thyroid stimulating immunoglobulin
(TSI)An antibody that targets TSH receptors
to stimulate TSH secretion (from anterior pituitary)
TSI not subject to negative feedback8x more common in womenbetween ages 20 – 40
Grave’s Disease Symptomsprotruding eyeseye irritation and double vision
Hyperthyroidism: Other CausesOveractive thyroid gland that produces
too many thyroid hormones without requiring stimulation by TSH
Inflammation of the thyroid (thyroiditis)Pituitary tumorsToo much thyroid hormone medicationExcessive intake of iodine
Hyperthyroidism Treatment:Drug TherapyAnti-thyroid drugs (suppressive
medication)Block amount of thyroid hormone in
the blood streamPrevent iodine from entering thyroid
gland
Hyperthyroidism Treatment:Radioactive Iodine TherapyGiven when drug therapy failsRadioactive iodine-131Damages thyroid cells over timeThyroid gland shrinks returning
thyroid hormone to normal level.
Hyperthyroidism Treatment:SurgeryThyroidectomy: removal of all or
some parts of the thyroid glandPost-surgery, thyroid replacement
drugs may be necessary, depending on how much of the thyroid gland is left.
Hypothyroidism Symptomslow thyroxine releaselow glucose metabolism
weight gainfatiguedecreased heart release
4x more common in women than men
usually between ages 35 – 60
Hypothyroidism
Cause: Autoimmunity(Hashimoto’s Thyroiditis)Immune system attacks thyroid
glandInflammation of the thyroid gland
20x more common in womenbetween the ages 30 – 50Treatment: thyroid hormone
supplements
Hypothyroidism: Other CausesIodine deficiencyThyroid gland dysfunction:
producing too little thyroid hormones
After radiation therapy with radioactive iodine
After a thyroidectomy
Comparing Symptoms
Hyperthyroidism Hypothyroidism
Weight Loss but good appetite GainBody Function
Increased bowel movementLight/absent menstrual periods
ConstipationHeavy menstrual periods
Temperature
Warm/moist skin, Feel hot
Feel cold
Neurological
Fatigue, InsomniaIrritability, Nervousness
FatigueSlowed thinking
Others Bulging eyes, goiter Dry skin
Calcium Regulation
Antagonistic hormones:PTHcalcitonin
Calcium Storage
99% stored in bonesIn cells: mitochondria
and ERIn skeletal muscles:
sarcoplasmic reticulum (SR)
http://www.bio.miami.edu/~cmallery/150/neuro/SR2.jpg
Calcium Function
MusclesCa levels inside muscle cells change
when muscles contractNerves
Ca stimulate release of neurotransmitters
Bone Cells
Osteoblast: bone-forming cells, take Ca from blood to build into bones
Osteoclast: break down Ca in bones and release into blood
Parathyroid Gland
4 small oval shaped glands
Located behind the thyroid glands
Each lobe of thyroid gland is adjacent to 2 parathyroid gland
Secretes parathyroid hormone (PTH)
Parathyroid Hormone (PTH)Peptide hormone Continuously produced (tonic
secretion) Stimulated by a decrease in blood
calcium (hypocalcemia)
PTH Targets
BoneInduces osetoclastDecompose bone to release stored Ca
into bloodKidney
Stimulates reabsorption of calciumConverts vitamin D precursor to active
vitamin D
Vitamin D
Steroid hormoneCan be ingested in food or formed in
skin when exposed to sunlightActivated form of vitamin D
reinforces the effect of PTHIncrease calcium in blood
Vitamin D Targets
Bone: release CaIntestine: Stimulates absorption of
calcium
Calcium Regulation
Low blood Ca(hypocalcemia)
PTH releasedBy parathyroid glands
Activation ofVitamin D
BoneKidney Intestine
Increasereabsorption
Stimulate osteoclast
Decomposebone
Increaseabsorption
Calcitonin
Peptide hormoneSecreted by thyroid glandStimulated by increase of blood
calcium (hypercalcemia)Antagonist of PTH: decreases blood
calcium
Calcitonin Targets
BoneStimulates Ca uptake into bones Inhibits osteoclastsLess bone tissue removal
Kidney Inhibits Ca reabsorption Increases rates of Ca loss by urinatinghigher concentration of Ca in urine
Intestine inhibits Ca absorption
http://www.bio.miami.edu/~cmallery/150/physiol/c45x1ca-regulation.jpg
Hypoparathyroidism
Causes:absent parathyroid from birthaccidental removal upon thyroid removal
Symptoms:decreased Ca levels in blood (hypocalcemia)sensitive nervesuncontrollable spasms of the limbs
Treatmentdaily calcium and vitamin D supplements
Hypocalcemia Symptoms
Tetanyan increased excitability of the nerves
(nerves are more likely to respond to less intense stimuli)
results in uncontrollable, painful spasms of the face, hands, arms, and feet
Seizures
hypocalcemia
parathyroid gland release PTHincreased Ca2+ levels
increased Ca2+ uptake in intestines (diet) &
kidneys (reabsorption)
increases osteoclast activity
activation of vitamin D; required for Ca2+ absorption
Hypocalcemia
Hyperparathyroidism
Causes:tumors on the parathyroid
glandSymptoms:
kidney stonesaches & painsosteoporosisdepression & fatigue
Treatment:removal of parathyroid tissue
Hypercalcemia SymptomsStones (Kidney Stones)Bones (Bone Pain)Groans (Constipation)Moans (peptic ulcer, pancreatitis)Overtones (Depression/ Confusion)
hypercalcemia
thyroid gland release calcitonindecreased Ca2+ levels
inhibits Ca2+ absorption by intestines
decreases osteoclast activity
Hypercalcemia
Osteoporosis
Loss of density in bones, leading to fragile bones
CausesHyperparathyroidism
Hyperactive Parathyroid (high levels of PTH)Hypovitaminosis D
Lack of Vitamin D in diet Decrease in enzyme catalyzing Vitamin D
Over activity of osteoclasts
Osteoporosis Symptoms
increase risk of bone fracturesJoint painkyphosis (hunchback)
http://www.youtube.com/watch?v=rHyeZhcoZcQ&feature=related