Thyroid Drugs

Question 1

Thyroid Hormones

Answer 1

T3 - Triiodothyrine (3x more active than T4) (20% made in Thyroid, rest peripheral)
T4 - Thyroxine (100% made in thyroid)
Calcitonin

Question 2

Thyroid Hormone Preparations

Answer 2

Liothyrine (T3)
Levothyroxine (T4)
Liotrix (T4 and T3 - 4:1)
Uses: Hypothyroidism (Cretenism, Child and Adult [Hashimoto’s]), Myxedema Coma (End Stage Untreated Hypothyroidism)

Question 3

Anti-Thyroid Drugs: Thioamides

Answer 3

Propylthiouracil (PTU) [*Inhibits peripheral T4->T3][SE: Hepatits] [BETTER FOR PREGNANCY]
Methimazole
Carbimazole
Common MOA: Inhibit Thyroperoxidase, block iodine oxidation, coupling of MIT and DIT
Toxicity: Flat itchy rash, Agranulocytosis, Fetal Thyroid (Meth and carb only)

Question 4

Anti-Thyroid Drugs: Anion Inhibitors

Answer 4

Perchlorate (ClO4-)
Pertechnetate (TcO4-)
Thiocynate (SCN-)
Use: Block uptake of Iodide by gland via Competitive Inhibition of Iodide Txp
SE: Aplastic Anemia

Question 5

Anti-Thyroid Drugs: Iodine & Iodides [Iodine Salts]

Answer 5

Na Iodide
K Iodide
Lugol’s Iodide (I2 & KI)
Use: Inhibit hormone release, Preop ddrugs by decreasing vascularity, Rapid improvement of Thyrotoxic Symptoms in 2-7 days
Limitations: Thyroid Escape 2-8 weeks
TOXICITY: Pimple Rash, Swollen Salivary Glands. Rhinorrhea, Conjuctivitis, Anaphylactic Reactions, Mucous membrane ulceration

Question 6

Iodine Contrast Media

Answer 6

Diatrizoate

Iohexol

Question 7

Radioactive Iodine I-131

Answer 7

• PO (rapid)
• Beta Radiation on Thyroid
• Slow destruction of thyroid
• Cheap alternative to surgery
  SE: Slow onset hypothyroidism in 80%
  CI: Pregnancy, Young Pts

Question 8

Adrenoreceptor Blocking Agents

Answer 8

Metaprolol
Atenolol
Propanolol
USE: Inhibit thyrotoxicosis symptoms (Palpitation, Nervousness, Tremors)

Question 9

Grave’s Disease Tx

Answer 9

Radioactive Idine (Preferred for >21 & w/o heart disease)
Methimazol
Propylthiouracil (PTU)

Question 10

Toxic Adenoma Tx

Answer 10

Radioiodine

Question 11

Toxic Multinodular Goiter Tx

Answer 11

Thioamides (Methimazole, Carbimazole, PTU)

Question 12

Thyroid Storm Tx

Answer 12

Propylthiouracil
Propanolol
Potassium Iodide (KI)
Dilatezem (CC Blocker)
Hydrocortisone
SUPPORTIVE THERAPY: Fever, Heart Failure, Any Dx that precipitates storm

Question 13

Amiodarone Induced Thyrotoxicosis

Answer 13

Type I - PTU (Iodine Induced)

Type II - Corticosteroids (Inflammatory)

Question 14

Thyroid Radiation Exposure

Answer 14

Potassium Iodide (KI)