1. Thyroid hormones 3 – the Abnormalities Lecture NO: 2nd MBBS
Dr Muhammad Ramzan

2. TH abnormalities - the definition
It refers to the ability of the thyroid gland to produce its secretions that are too high or too low for:
The body requirements
THs can be produced in excess or there may be deficiency of THs
Both the conditions give rise to important clinical conditions that are not compatible with comfortable life

3. TH abnormalities --The background
Although TH are not strictly necessary for life.
They have profound effects on many physiological processes like development , growth and metabolism
Deficiency of TH is not compatible with normal life

4. TH abnormalities –The types
TH abnormalities may be related either to:
Deficiency or excess and affects all the body cells – the
Targets for the thyroid hormones

5. TH abnormalities – the excess Thyroid is over active
Excess of TH refers to hyperthyroidism
Thyroid gland is overactive in hyperthyroidism and produces more hormones than body requirements
It is also called as Thyrotoxicosis

6. TH excess – Hyperthyroidism in general ↑ FT4 FT3 and normal TSH
TH excess is characterized by :
Increase in Basal metabolic rate - BMR
Increased heat production and oxygen consumption through increased hydrolysis of ATP
Elevation of FT3 / FT4 with normal TSH

7. Effects of Hyperthyroidism
Effects of hyperthyroidism are classified into 2 based upon the effects on various tissues/nutrients
Hyperthyroid effects
Effects on the metabolism of :
Proteins, Lipids and Carbohydrates

8. Hyperthyroid effects Hyperthyroid effects include:
Weight loss due to ↑in body metabolism/BMR
Warm hands with high coloured skin; rapid and irregular pulse, perfused eyes for hyper dynamic circulation
Tolerance to cold for ↑BMR
Tremours of hands for nervous excitibility
Exophthalmose – reason ?

9. Hyperthyroidism – perfused face

10. Hyperthyroidism – Bulging eyes/ Exophthalmos

11. Excess of TH – the metabolic effects
Hyperthyroidism affects the metabolism of :
Carbohydrates (CHO)
Lipids and
Proteins

12. Effects on Protein metabolism
TH excess increases protein breakdown /Proteolysis and releases more amino acids in plasma.
Promotes Gluconeogenesis for ↑ in plasma Amino acids
Proteolysis results in reduction of body weight; muscle weakness, growth and development in children
Reduces protein synthesis/ Proteogenesis

13. Effects on Lipid metabolism promotes lipolysis
TH excess stimulates fat mobilization leading to lipolysis and increases :
Free fatty acid level in plasma
Fatty acid oxidation to generate energy
Reduces TG synthesis and adipose tissue mass and
Lowers Plasma Cholesterol and TG

14. Effects on Carbohydrate (CHO) metabolism
TH stimulate all the aspects of CHO metabolism and promotes the :
intestinal absorption of glucose
Glucose uptake by the body cells and glycolysis
Break down of glycogen – Glycogenolysis
Reduces glycogen synthesis/ Glycogenesis and
Increases Gluconeogenesis

15. TH abnormalities – The deficiency Thyroid gland is underactive
It is the inability of thyroid gland to produce enough TH for body requirements.
Thyroid gland is under active
The condition is called hypothyroidism or myxoedema
It is more common in females

16. TH deficiency /hypothyroidism in general ↑TSH normal FT3/T4
Hypothyroidism results in slowing down of basal metabolic rate – BMR and
Reduction in : Metabolism;
Oxygen consumption
Heat production and hydrolysis of ATP
Elevation of TSH, normal TF3 or FT4

17. Effects of hypothyroidism
Effects of hypothyroidism are classified into 2 based upon the effects on various tissues/nutrients
Hypothyroid effects
Effects on the metabolism of :
Proteins, Lipids and Carbohydrates

18. Hypothyroid effects These effects include:
Weight gain for the subcutaneous deposition of Muco polysaccharides
Dry; rough and hairless skin for =====
Expression less face, non pitting /pretibial oedema ==A diagnostic sign
Cold hands and extremities for slow circulation
Low body temperature and cold indolence for ↓BMR
Slow reflexes and mental sluggishness for Mental depression
Constipation

19. Hypothyroidism – Mental sluggishness

20. Hypothyroidism in females – swollen/ expression less face

21. Non pitting edema of feet

22. Pretibial Myxoedema

23. Deficiency of TH – the metabolic effects
TH deficiency suppresses the metabolism of :
Carbohydrate
Lipids and
Proteins

24. The deficiency – Effects on protein metabolism
Hypothyroidism reduces Proteogenesis and promotes proteolysis especially in skeletal muscles
Excess of glucoplastic amino acids are released from the skeletal muscle break down
These Amino acids are used as substrate for hepatic Gluconeogenesis

25. The deficiency – Effects on Lipid metabolism
Dyslipidemia is commonly observed in hypothyroidism
This includes ↑ in plasma levels of :
TG, Total Cholesterol and LDL- Cholesterol
Low HDL- Cholesterol
Increase in body adipose tissues and reduction in fatty acid oxidation

26. TH deficiency – Effects on CHO metabolism
Hypothyroidism suppresses :
All aspects of CHO metabolism
Reduces intestinal absorption of glucose and uptake of glucose by the body cells (Skeletal muscles and Fatty tissues)
Lowers Glycolysis, release of energy and ATP production and body temperature

27. The deficiency – Effects on CHO metabolism cont.
Produces hyperglycemia/ Diabetes mellitus for inhibiting Insulin secretion and promoting its degradation
↓ glycogen synthesis (Glycogenesis) and its storage in liver
↑Deposition of Glycosaminoglycans,mucopolysaccarides and Hyaluronic acid under the skin giving rise to :
Non pitting edema – a hallmark of hypothyroidism

28. TH deficiency in infants and children Juvenile hypothyroidism
Congenital hypothyroidism refers to hypothyroidism
A deficiency or lack of TH at birth
If deficiency of TH is not detected earlier, it will lead to deficiency in IQ and development of CNS

29. Hypothyroidism in infants and children – the presentation
Infants are lethargic ,have slow movements and low body temperature
They have big head, protruding tongue , puffy face and feeding problems
Results of treatment are excellent ,if started earlier