The thyroid gland is a butterfly-shaped organ located in the neck below the larynx. It is composed of follicles containing colloid surrounded by follicle cells that produce thyroid hormones like T3 and T4. The hormones regulate metabolism and are synthesized through a process involving iodine uptake, incorporation into the hormones, and diffusion out of the gland. Disorders can arise from abnormal hormone secretion levels like hyperthyroidism and hypothyroidism, or from non-toxic goiter causing gland enlargement without excess hormones.

1. THYROID GLAND

2. CONTENT TO BE COVERED
Anatomy and Physiology of thyroid gland
Microscopic structure of thyroid gland
Thyroid hormone synthesis, secretion and storage
Pathological role of thyroid hormone
Thyroid hormone and their disorders

3. Anatomy and Physiology of thyroid gland
• A butterfly-shaped organ
• the thyroid gland is located anterior to the trachea, just
inferior to the larynx The medial region, called the
isthmus, is flanked by wing-shaped left and right lobes.
• Each of the thyroid lobes are embedded with
parathyroid glands, primarily on their posterior surfaces.

4. • Lobe size 5 cm long and 3cm width; cone
shaped lope
• Organ weight is 25 g
• This organ developed 3 months of age
• Location 5,6,7th cervical and 1st thoracic
vertebrae
• Blood supply: Arterial blood supply to the
gland through the superior and inferior thyroid
gland

5. • The tissue of the thyroid gland is composed
mostly of thyroid follicles. The follicles are
made up of a central cavity filled with a sticky
fluid called colloid.
• Surrounded by a wall of epithelial follicle
cells, the colloid is the center of thyroid
hormone production, and that production is
dependent on the hormones’ essential and
unique component: iodine.
• Between the follicles single or small groups
cells; parafollicular cells, also called as c-cells
which secrete the calcitonin hormone

6. Microscopic structure of thyroid gland

7. Thyroid hormone
Hormone :
A hormone is any member of a class of
signalling molecules , produced by glands in
multicellulae organisms, that are transported
by the circulatory system to target the distant
organs and regulate physiology and behavior.
Thyroid hormones:
 T3(tri iodothyronine)
 T4 (thyroxine)
 Calcitonin

8. Synthesis Storage and Release
Four Main Steps
Uptake of iodide
Incorporation : iodide into iodine
Coupling of iodine to form thyroid hormone
Diffusion of thyroid hormone

11. Physiological Function of T3 and T4
• Improve the mental strength
• Enhances the effect of other hormones like
adrenaline and nor adrenaline
• Increasing the basal metabolic rate and heat
production
• Regulating the metabolism of carbhohydrates,
proteins and fats

12. Calcitonin
• This hormone secreted by the parafollicular or
C-cells in thyroid gland
• It acts on bone cells and the kidneys to reduces
the blood calcium levels when they are raised .
• It promotes storage of calcium in bones and
inhibits the reabsorbtion of calcium by the
renal tubules

13. Thyroid gland disorders
Two main categories
• Abnormal secretion of thyroid hormones
-Hyperthyroidism
-Hypothyroidism
• Goitre

14. Hyper thyroidism
• Also known as thyrotoxicosis
• Body tissues are exposed to excessive T3 and T4
• It increases the basal metabolic rate.
Hypothyroidism
• Insufficient T3 and T4 secretion
• It causes the congenital hypothyroidism in
childrens
• Myxoedema in adults.

15. HYPERTHYROIDISM

24. Goitre
• Enlargement of the thyroid gland without signs
of hyperthyroidism
• Relative lack of T3 and T4, low level
stimulation of TSH resulting in hyperplasia of
the thyroid gland.
Reasons:
• Persistent iodine deficiency
• Genetic abnormality affecting the T3 and T4

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