Download Thyroid Hormones

Thyroid Hormones
Normal Functions
Hyperthyroidism
Hypothyroidism
2-May-17
Thyroid Hormones
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Thyroid Hormones
 Two
principal hormones
Thyroxin (T4)
 Triiodothyronin (T3)

 Others
Calcitonin
 Parathyroid hormones

2-May-17
Thyroid Hormones
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Thyroid Hormones Effects
Cellular metabolic activity
 Thyroid hormone





2-May-17
 Metabolic activity of almost all tissues
BMR can  to 60 – 100% above normal
Rate for utilization of food for energy is
increased
Rate of protein synthesis  but also the rate of
prot catabolism 
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Thyroid Hormones Effects
Growth rate of young people accelerated
 Mental processes excited
 Activity of most other endocrine glands are
increased
 Increase in mitochondria
 Increase membrane active transport
mechanism

2-May-17
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Effect on Growth

In children

Hypothyroid causes


Retarded growth
In those who are hyperthyroid
Excessive skeletal growth
 Giant


Thyroid hormone promote growth and
development of brain

2-May-17
During fetal life
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Effect on Carbohydrate

Stimulate all aspect of carbohydrate
metabolism





2-May-17
Uptake of glucose by cells
Enhanced glycolysis
Enhanced gluconeogenesis
 Absorption by GIT
 insulin secretion
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Effect on Fat
Thyroid hormones
 Enhance all aspects of fat metabolism


Rapid mobilization of lipids from adipose tissues



2-May-17
 In fat stores
 in FFA conc in plasma
Increased FA oxidation by cells
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Effect on Fat
Effect on plasma & liver fat
  Thyroid hormones




 conc of cholesterol, phospholipids, TG in
plasma
But increase FFA
 Thyroid hormones


2-May-17
Increase conc of cholesterol, phospholipids, TG
Cause excessive deposition of fat in liver
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Effect on Fat
Cholesterol can lead to
artherosclerosis
 Thyroid hormone


2-May-17
Increase cholesterol secretion in bile
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Specific effects
 On

CVS
Decrease TPR
 Heat

& waste products
Increase 2:3 DPG
 Relative

tissue hypoxia
Increase sensitivity and number
 Β-adrenergic
receptors
 ↑ CO

2-May-17
Increase blood flow to all tissues except
brain
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Specific Effects

Increase O2 consumption in most tissue
except


Testes, brain, erythrocytes, spleen
GIT

Increase absorption of


Vitamins A, B12, Iron
CNS Promote normal



Brain development
Myelination
Excitability of tissues & reflexes

2-May-17
Potentiation of catecholamines
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Abnormal Thyroid
Functions
Hyperthyroidism
Hypothyroidism
2-May-17
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Hyperthyroidism
Primary
Secondary
2-May-17
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Primary Hyperthyroidism
 Associated
with
Low
TSH
Hyperplasia of the gland
 An
auto immune response
 More than 50% of patients
Show
eye signs
Grave’s disease
2-May-17
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Primary Hyperthyroidism
 Grave’s
diseases
 Exophthalmic
goiter
 Thyroid gland becomes
 Enlarged
 Hyperplastic
 Long acting thyroid stimulator (LATS)
 Long acting thyroid stimulator protector
(LATS-protector)
 TSH
2-May-17
levels normal
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Secondary Hyperthyroidism
 Hypothalamic
or pituitary in origin
 Associated with high plasma THRH
 Plasma TSH levels are raised
2-May-17
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Clinical Manifestation

These are exaggerated effects of

Normal thyroid functions on



CVS, GIT, CNS
Metabolism
These include





2-May-17
Heat intolerance
Raised CO
 HR
Emotional irritability
Fine tremors
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Complications of
Hyperthyroidism
Exopthalmos
 High output cardiac failure
 Inadequate tissue perfusion



Despite the compensatory  Co
Liver failure

 demand energy, vitamins

Depletion of vit A, B12
 Anaemia

Depletion of glycogen

2-May-17
Liver becomes more susceptible to injury & failure
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Hypothyroidism
 Decreased
or suppressed TH activity
 Could
Primary hypothyroidism
 Secondary hypothyroidism

2-May-17
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Primary hypothyroidism
 Decreased
TH

Due to diseases of the thyroid gland
 Associated

with autoimmune response
Hashimoto’s disease
 Some
goiter
2-May-17
or suppressed activity of
are due to idiopathic non-toxic
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Secondary Hypothyroidism
 May
be due to
Failure of pituitary or hypothalamus
 Iodine deficiency
 Presence of goitrogenic substances

 Carbamazole
 Cabbages
2-May-17
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Secondary Hypothyroidism
Thyroid gland respond to a dose of TSH
 To differentiate hypothyroidism



Secondary for Pituitary or hypothalamic failure
Exogenous TRH administration


2-May-17
 in plasma TSH if the problem is due to
hypothalamic failure
There is no  in plasma TSH if the failure is of
pituitary gland
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Manifestations of
Hypothyroidism

In adults


Called myxodema
Characteristic skin changes






BMR falls to about 40% of normal
Poor tolerance to cold
Voice husky and slow
Mental activity


2-May-17
Skin dry, yellowish (carotenemia)
Carotene retention in the skin
Slow, poor memory
Severe mental illness (myxodema madness)
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Manifestations of
Hypothyroidism

In children and young

Cretinism


Mentally retarded dwarfs



Speech problems
Pot bellied due to

2-May-17
Reduced nerve cells and axons in CNS
Reduction in myelination
Enlarged protruded tongue


Dwarfed, retarded growth
Accumulation of fluids in abdominal cavity
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