Thyroid Pharmacology Flashcards Preview

Endocrinology > Thyroid Pharmacology > Flashcards

Flashcards in Thyroid Pharmacology Deck (22):
1

Does T3 or T4 have a shorter half life?

- T3= 1 DAY (compared to T4= 1 week)
*important because you will give T3 to someone in a hypothyroid state.

2

What is responsible for regulating the conversion of T4 to T3 in the periphery?

- deiodinase-1 (D1)= a peroxidase enzyme that is involved in the activation or deactivation of thyroid hormones.
*D2 is the same, but found only in the brain.

3

To what do T3 and T4 bind in the blood in order to be transported?

- thyroxine-binding globulin (TBG)
*tranthyretin only binds T4

4

How do you distinguish between primary, secondary, and tertiary HYPOthyroidism?

- PRIMARY= TH deficiency (TH levels do NOT increase with administration of TSH). Ex. Hashimotos
- SECONDARY= TSH deficiency (TSH levels do NOT increase with administration of TRH). Ex. Sheehan's
- TERTIARY= TRH deficiency (increased TSH levels with administration of TRH).

5

**** What is the most common drug replacement hormone for HYPOthyroidism?

- LEVOTHYROIXINE sodium (T4)
*used over liothyronine sodium (T3) bc it has a much longer half life.

6

Is there an advange to combining T4/T3 to treat hypothyroidism?

- not really.

7

What is an ADR of Levothyroixine?

- hyperthyroidism if you give too much.

8

What are the limited uses of Liothyronine (T3)?

- T3 suppression to differentiate hyperthyroid from euthyroidism.
- short term supppresion of a solitary thyroid nodule before radioactive iodine scan.

9

What is Thyrotoxicosis (hyperthyroidism); Grave's disease?

- antibody against the TSH receptor, leaing to a toxic multinodular goiter

10

How do you treat Thyrotoxicosis (hyperthyroidism); Grave's disease?

- inhibit thyroidal secretion via surgery or radiation.

11

**** How do you treat thyroid storm (potentially fatal thyrotoxic crisis)?

- sedation, O2, decrease body temp, antithyroid meds, iodine, CORTICOSTEROIDS, fluids, electrolytes, and B-BLOCKERS.

12

What are the antithyroid agents?

- Methimazole
- Polythiouracil (PTU)
- Potassium perclorate (KCLO4)
- Potassium iodide (KI)
- Iodine 131
- B-adrenergic blockers (PROPRANOLOL)

13

**** What is Methimazole?

- inhibitor of iodine incorporation to tyrosine residues (MIT and DIT).
- preferred over PTU to treat hyperthyroidism (lower risk of liver injury).
- similar to PTU but no inhibition of T4 to T3 in periphery.

14

What is an ADR of Methiomazole?

- AGRANULOCYTOSIS

15

**** What is Propylthiouracil (PTU)?

- same as methimazole, but also inhibits T4 to T3 in periphery.
- shorter half life than Methimazole.

16

What ADR does PTU have in addition to agranulocytosis (like Methimoazole)?

- severe HEPATITIS

17

Are Methiomazole and PTU contraindicated in pregnancy?

- YES (DO NOT USE)

18

What is Potassium perchlorate (KClO4)?

- interferes with Iodide transport into thyroid gland, but not used much anymore bc it can cause severe aplastic anemia.

19

**** What is Potassium Iodide (Lugol's solution)?

- transiently inhibits organificaiton (iodine formation).
- inhibits hormone release.
- inhibits accumulation of radioiodine.
*used as PREOPERATIVE PREPARATION for THYROIDECTOMY and for THYROID STORM.

20

**** What will Iodine 131 (radioactive) do?

- PERMANENTLY reduces TH production.
*mainly used for pts with Grave's disease

21

Why would we use a Beta blocker during thyrotoxicosis?

- to decrease hyperthyroid-induced tachycardia, tremor, sweating, heat intolerance, and anxiety.

22

What are the contraindications for Beta-blockers (propranolol)?

- obstructive airway disease (blocks bronchodilation).
- causes hypoglycemia in diabetics.