prepared by medical practitioner Dr.HARI BASKAR ,from Coimbatore,India, is well versed in physiology and general medical sciences is a most common reference author in this subject.This presentation focuses on the metabolic actions of thyroid hormone-THYROXIN.

1. The role of thyroid hormones in
the regulation of metabolism.
By….S.Hari Baskar

2. THYROID GLAND
• Thyroid gland
synthesizes two
major of hormones:
Thyroxine and
Triiodothyronine

4. Functions of iodine containing hormones
Necessary for
normal growth,
differentiation,
sexual and mental
development
Regulate the rate
of metabolism

5. • Required for Growth
Hormone action
• Increases mitochondrial
oxidative
phosphorylation
• Increases activity of
adrenal medulla
• Induces enzyme
synthesis
• Result:Stimulation of
growth of tissues and
increased metabolic rate
along with Increased
heat production
Anabolic Actions of Thyroid Hormone

6. • About 1/3rd of all ATP in the body is used by the
Na+
/K+
ATPase
• T3 increases the synthesis of Na+
/K+
pumps, markedly
increasing ATP consumption.
• T3 also acts on mitochondria to increase ATP
synthesis
• The resulting increased metabolic rate increases
thermogenesis (heat production).
One Major Target Gene of T3:
The Na+
/K+
ATPase Pump

7. Calorigenic action
• Stimulates heat
production in body
secondary to increased
oxygen consumption
which increases BMR.
• Exception:- Adult brain
,Testis, Lymph nodes,
Ovary, Uterus, Anterior
pituitary.

8. •In physiological
concentration it is
anabolic causing a
positive nitrogen
balance
Effect of thyroxine and
triiodthyronine on the protein
metabolism:

9. • In the increased
concentration it is catabolic
causing negative nitrogen
balance
• Thus muscle weakness and
cretinuria are common
manifestations of a
Hyperthyroid patient.

10. Effect on carbohydrate
metabolism
T3 and T4 leads to overall increase in
enzymes causing
• Increased glucose absorption from GIT
.

11. • Acceleration of Glucose
metabolism-Rapid
uptake by cells,
Enhanced glycolysis
and increased insulin
secretion and its effects
on carbohydrate
metabolism.
• Thus hyperthyroidism
causes Diabetes mellitus

12. Effect on Fat metabolism
• Mobilization of fat from the
Adipose tissue.
• Increase in level of free
fatty acid
• Enhanced oxidation of free
fatty acids by cells of body.
• Decrease in Quantity of
cholesterol, Phospolipids
and TAG in plasma.
• All these factors leads to
incresed loss of weight.

13. • Decrease in plasma
cholesterol is due to increased
excretion in BILE.
• P.Chloesterol level drops
even before increase in BMR,
Showing that the action is
independent of oxygen
consumption.
• So, Hypothyroidism is
associated with elevated
plasma cholestrol levels,
which can be reversed by
thyroid administration.

14. Vitamin metabolism
• Thyroid hormones
increase the quantity of
enzymes
• Vitamins are essential for
some parts of enzymes
and co-enzymes
• Thus, Thyroid hormones
results in increased need
of Vitamins.
• This is the reason for
vitamin deficiency in
Hyperthyroidism.
E.g. Excess thyroxin causes
depletion of niacin leading to
decrease in NADH concentration .

15. On Water and Electrolyte balance
• Has a significant role in
regulation of water and
electrolyte balance.
• Impairment of thyroid
function results in
accumulation of Water and
electrolytes which can be
reversed by administration of
these hormones.

16. Permissive actions……
• T3 and T4 potentiate the stimulatory effects
of Epinephrine, Nor-Epinephrine,
Glucagon, Cortisol and Growth hormone on
Gluconeogenesis, Lipolysis, Ketogenesis
and Proteolysis of liable protein pool.

17. On Sleep………
• Due to exhausting
effect of thyroid
hormone on the
musculature an CNS,
the hyperthyroid
subject has a feeling of
constant tiredness, But
because of the
excitable effects of
thyroid hormone on
the synapses, it is
difficult to sleep.