Download MBBS Physiology Presentations 7 Thyroid Hormones Lecture Notes

--- Content provided by​ FirstRanker.com ---

Thyroglossal duct marks the path of

thyroid from tongue to neck

Gland is highly vascularized and has

--- Content provided by FirstRanker.com ---

one of the highest rates of blood flow

per gram of tissue
Thyroxine (T4)- Greater amount

--- Content provided by⁠ FirstRanker.com ---

released. Biological activity less

Triiodothyronine (T3)- Lesser amount

--- Content provided by‌ FirstRanker.com ---

released. Biologically more active.

Generated at the site of action in

peripheral tissues by deiodination of

--- Content provided by‍ FirstRanker.com ---

T4.

Reverse

--- Content provided by‍ FirstRanker.com ---

Triiodothyronine (RT3)-

Small amounts
Pendrin (Cl/I exchanger)

--- Content provided by‍ FirstRanker.com ---

Pendred syndrome- Thyroid dysfunction

and deafness

Salivary

--- Content provided by​ FirstRanker.com ---

glands, Gastric mucosa,

placenta, ciliary body of eye, choroid

--- Content provided by‍ FirstRanker.com ---

plexus, mammary glands and certain

cancers of these tisssues express NIS

but the transprter is not affected by TSH

--- Content provided by‌ FirstRanker.com ---

in these tissues.
T4 and T3 are deiodinated in liver, kidneys

and other tissues

--- Content provided by FirstRanker.com ---

Pituitary and cerebral cortex has high T3/T4

ratio

--- Content provided by​ FirstRanker.com ---

Three deiodinases: D1, D2 and D3- contain

selenocysteine

D1 ? present in liver, kidneys, thyroid and

--- Content provided by​ FirstRanker.com ---

pituitary

D2- present in brain, pituitary and brown

--- Content provided by‍ FirstRanker.com ---

adipose tissue

D3- present in brain and reproductive tissues
T4 and T3 increase oxygen consumption

--- Content provided by⁠ FirstRanker.com ---

of all metabolically active tissues except :

Adult brain
Testes
Uterus

--- Content provided by​ FirstRanker.com ---

Lymph nodes
Spleen
Anterior pituitary
o T4 depresses oxygen consumption of

--- Content provided by‍ FirstRanker.com ---

anterior pituitary because it inhibits TSH

secretion

Thyroid hormones increase the activity

--- Content provided by⁠ FirstRanker.com ---

of membrane bound Na-K ATPase

Some calorigenic effect is due to

--- Content provided by‍ FirstRanker.com ---

metabolism of fatty acids they mobilize
Nitrogen excretion is increased
Potassium released due to protein

catabolism is excreted in urine

--- Content provided by‌ FirstRanker.com ---

Increased urinary hexosamine and

uric acid excretion

--- Content provided by FirstRanker.com ---

Need for vitamins is increased due to

increased BMR

Thyroid hormones are necessary for

--- Content provided by​ FirstRanker.com ---

hepatic conversion of carotene to

Vitamin A

--- Content provided by​ FirstRanker.com ---

Thyroid

hormones increase the

number and activity of mitochondria

--- Content provided by FirstRanker.com ---

Thyroid hormones increase active

transport of ions through cell

--- Content provided by‍ FirstRanker.com ---

membranes.
Stimulation

of

--- Content provided by⁠ FirstRanker.com ---

carbohydrate

metabolism

Stimulates rapid uptake of glucose by

--- Content provided by​ FirstRanker.com ---

cells

Glycolysis is increased
Gluconeogenesis is increased

--- Content provided by‍ FirstRanker.com ---

Increased reabsorption from GIT
Increased insulin secretion

Stimulation of fat metabolism:
Lipid are mobilized rapidly from fat

--- Content provided by FirstRanker.com ---

tissue

Decreases fat stores of the body
Increases free fatty acid concentration

--- Content provided by​ FirstRanker.com ---

in plasma

Increased thyroid hormones decrease

--- Content provided by​ FirstRanker.com ---

the concentration of cholesterol,

phospholipids and triglycerides in the

plasma

--- Content provided by⁠ FirstRanker.com ---

Increase cholesterol secretion in bile

Increased thyroid hormones increase

LDL receptors on the liver leading to

--- Content provided by‌ FirstRanker.com ---

rapid removal from plasma

Increased requirements of vitamins
Increases basal metabolic rate

--- Content provided by‍ FirstRanker.com ---

Decreased body weight
Increases respiration
Increased gastrointestinal motility
Increased

--- Content provided by‌ FirstRanker.com ---

activation

of

Reticular

--- Content provided by​ FirstRanker.com ---

Activating system (RAS)

Affects brain development
Cerebral cortex, basal ganglia

--- Content provided by⁠ FirstRanker.com ---

and

cochlea are mainly affected

--- Content provided by‌ FirstRanker.com ---

Deficiency causes during development

causes mental retardation, motor

rigidity and deafness.

--- Content provided by​ FirstRanker.com ---

Exerts effects on reflexes- Reaction time

of reflexes is increased in hypothyroidism

--- Content provided by FirstRanker.com ---

and decreased in hyperthyroidism

In hypothyroidism, mentation is slow

and CSF protein levels increased

--- Content provided by⁠ FirstRanker.com ---

Thyroid

hormones revert these

--- Content provided by FirstRanker.com ---

changes

Cerebral blood flow, glucose and

oxygen consumption are normal in

--- Content provided by⁠ FirstRanker.com ---

both hypo and hyperthyroidism
Increases blood flow and cardiac

output

--- Content provided by⁠ FirstRanker.com ---

Increases heart rate
Increases heart strength
Pulse pressure increases
Increases expression of - MHC,

--- Content provided by⁠ FirstRanker.com ---

sarcoplasmic reticulum calcium

ATPase, K- Channels

--- Content provided by⁠ FirstRanker.com ---

Inhibits - MHC, Phospholamban,

adenylyl cyclase, nuclear receptors,

Na-Cl exchangers

--- Content provided by FirstRanker.com ---

Increases

rate and force of

--- Content provided by‍ FirstRanker.com ---

contractions