Latest Questions With Complete Grade A Answers

2024 CPPS 303 - Endocrinology 1 (Thyroid Hormone and Function ) Latest Questions With Complete Grade A Answers

• Thyroid Gland

Answer: On the anterior surface of the trachea

• Has left and right lobes
• Small connecting branch (isthmus)

Gland size varies with environmental factors

• 2 Cell types of Thyroid gland

Answer:

1) Follicular Cells

• Secrete T4 and T3

2) Parafollicular Cells (C-cells)

• releases Calcitonin which regulates calcium and phosphate metabolism

• T3

Answer: tri-iodiothyronine

• T4

Answer: Thyroxine or tetra-iodiothyronine

• Palpability and swelling of thyroid gland

Answer: When it swells, we can feel and know something it wrong

• Cannot physically differentiate if there is hypothyrodism or hyperthyroidism

• Trace Elements of thyroid hormones

Answer: Require Iodine as trace element

• Need a constant supply of iodine

• How long can thyroid hormones last

Answer: They can be stored up to 3 months

• What kind of receptors are thyroid Hormone Receptors

Answer: Even though thyroid hormone is a peptide, they use nuclear receptors

(same as steroids) 1 / 2

• General Synthesis of Thyroid Hormone

Answer:

• Thyroid hormones are synthesized in the follicular epithelial cells
• Production requires iodine
• Synthesis is partly intracellular an partly extracellular
• Synthesized hormones are stored externally in the follicular lumen until the gland

is stimulated to release them

• Colloid

Answer: A glycoprotein mixture in the follicular lumen

• First part synthesized of the hormone

• Thyroid Stimulating Hormone (TSH)

Answer: Main hormone that regulates thyroid hormone synthesis

• From the anterior pituitary

• 8 Steps to thyroid hormone synthesis

Answer:

1) Synthesis of Thyroglobulin (TG) 2) Iodide Trapping 3) Oxidation of Iodide 4) Iodination of thyrosine 5) Coupling Reaction 6) Endocytosis of thyroglobulin 7) Hydrolysis of T3 and T4 from thyroglobulin 8) Deiodination

• 1) Synthesis of Thyroglobulin (TG)

Answer: In the Thyroid Follicular Cell

1) Thyroglobulin (TG - Colloid) is synthesized in the thyroid follicular cell (ER) 2) TG is then packaged into secretory vesicles 3) TG is exocytosed into the follicular lumen

• 2) Iodide Trapping

Answer: Na/I(iodine) symporter is located on the basolateral mem- brane of

follicular cell (faces blood stream)

• Iodine in the bloodstream enters into the follicular cell with Na+, fueled by the Na+

electrochemical gradient

• TSH enhances Na/I symporter activity
• / 2