Thyroid Physiology and Pharm

Question 1

What are the seven steps of Thyroid Hormone synthesis?

Answer 1

Dietary Iodide is transported into the thyroid follicular cell. Oxidation of Iodide to Iodine. Iodine is added to tyrosines to make MIT and DIT. Conjugation of MIT and DIT. Endocytosis of conjugates T3 and T4. Proteolysis of the conjugates. Movement of T3 and T4 out of the cell.

Question 2

What enzymes cause thyroid hormone activation?

Answer 2

Deiodinases I and II

Question 3

What enzymes cause thyroid hormone inactivation?

Answer 3

Deiodinases I and III

Question 4

What is Thionamide a drug target for?

Answer 4

Deiodinase I (liver, kidney). Converts T4 to T3 (active) and converts T4 to rT3 (inactive)

Question 5

What is Cretinism?

Answer 5

Hypothyroid disorder in infants. Effects of low thyroid in infants is physical and mental growth retardation, coarse hair and protuberant abdomen. If supplementation delivered later, patients physical development will recover but their mental deficits will be permanent.

Question 6

Hashimoto’s thyroiditis?

Answer 6

Chronic lymphocytic process of destruction (autoimmune). Antibodies react against proteins in thyroid gland and this causes destruction.

Question 7

What is Graves disease?

Answer 7

Production of immunoglobulins that actually stimulate the thyroid. TSI (thyroid stimulating immunoglobulins). T cells become sensitive to thyroid antigen which leads to stimulating B cells to produce antibodies that mimic TSH.

Question 8

What lab value best reflects the physiologic state of the thyroid axis?

Answer 8

Free T4 measurements better reflect the physiologic state of the thyroid axis.

Question 9

What is the normal range for TSH?

Answer 9

0.5-5

Question 10

Levothyroxine

Answer 10

T4. Used for hypothyroidism. Long ramp up to steady state (6-8 weeks). Used as long term treatment.

Question 11

Liothyronine

Answer 11

T3. Used for hypothyroidism in short term. Used when a quick onset of action is needed.

Question 12

Methimiazole

Answer 12

Inhibits thyroid peroxidase. Takes 2 weeks to work. Teratogenic effects. First line unless patient is pregnant.

Question 13

Propylthiouracil

Answer 13

Inhibits thyroid peroxidase and diodinase I. Used in pregnant patients. Otherwise it has increased risk of liver injury.

Question 14

Iodide

Answer 14

Used in preparation for thyroidectomy, treating a thyroid stores or protection from radioactive iodide. MOA - high iodide effects TH by blocking transport, release, synthesis

Question 15

Radioactive 131(I)

Answer 15

Used for destroying the thyroid. Main disadvantage is too much destruction can occur. Need to supplement TH after treatment.

Question 16

Radioactive 123(I)

Answer 16

Used for imaging the thyroid.