Pharm: L19: Thyroid Function

Question 1

Replacement Therapy

1. SYNTHROID
   a. What is it?
   b. Produces what?
   c. DOC for what?
   d. How are they given and why?
2. CYTOMEL (Liothyronine Sodium)
   a. What is it?
   b. When is it used?
3. Side effects?

Answer 1

1. a. T2
   b. Normal Levels of T3 and T4
   c. for Hypothyroidism
   d. Titrated Carefully (due to TSH levels…)
2. a. T3…Short half life and duration
   b. Sometimes at start of therapy but not used for maintenance
3. Similar to HYPERTHYROIDISM…so reduce dosage

Question 2

Replacement Therapy: Drug Interactions

1. What 2 drugs can Increase TBG
   a. What does increasing levels of this do?
   b. When is FREE T4 measured in women?
2. What 2 drugs DECREASE levels of TBG?

Answer 2

1. Estrogens and Tamoxifen (lecture he has Estrogens, Corticosteroids and Androgens listed)
   a. Reduce Clinical response to Levothyroxine (SYNTHROID)

b. When they’re on Thyroid Tx and Estrogens (need higher dosage of Synthroid usually)
2. GLUCOCORTICOIDS and ANDROGENS

Question 3

Replacement Therapy: Drug Interactions (Other)

1. Sympathetics
2. Warfarin
3. Diabetic Drugs
4. Corticosteroids

Answer 3

1. Cardiotoxic
2. Increase Degradation of Clotting Factors (Potentiates Warfarin)
3. Dosage change might be needed (PHARMACODYNAMIC INTERACTION, NOT Pharmacokinetic)`
4. Changes in Corticosteroid Metabolism (DECREASED in Hypothyroid Pts and INCREASED in HYPERTHYROID Pts)

Question 4

Replacement Therapy: Drug Interactions: T4 Effectors

1. Iodides and Lithium
2. Antacids
3. Phenytoin, Carbamazapine, Rifampin

Answer 4

1. INHIBIT release/Synthesis of Thyroid Hormones (AMIODARONE has IODIDE)
2. Can mess up Absorption of Levothyroxine (SYNTHROID) so it should be taken on an Empty Stomach
3. Induces Hepatic Enzymes. Increase Metabolism of SYNTHROID

Question 5

Clinical Signs of Hyperthyroidsim?

2. MOST COMMON CAUSE?

Answer 5

Tachycardia, Widened Pulse Pressure, Sensitivity to Heat, TREMOR, Weight Loss and Increased Appetite, Diarrhea, Increased Sensitivity to Adrenergic Stimulation.

2. GRAVES DISEASE (AI: Ab’s to TSH Receptor)…Stimulate Thyroid Gland and cause Hypersecretion that can lead to GOITER and Protrusion of eyes.

Question 6

What is a THYROID STORM

2. How to treat?

Answer 6

1. potentially Fatal Thyrotoxic Crisis in Hyperthyroid Pts after Trauma, Infection, Radioactive Iodine Tx, or Inadequate Preparation for Surgery.

(Hyperthermia, Dehydration, Tachycardia w/Arrhythmias, Behavior Changes, Vomiting and Diarrhea, Syncope and Coma

2. Sedation, O2, Antithyroid meds, Iodine, Corticosteroids, Fluids, Electrolytes, B-Blockers

Question 7

1. Consequences of Tx: Thyroidectomy and 131I?

Answer 7

1. Hypothyroidism.

131I = RISK of THYROID STORM

Thyroidectomy: Surgery risk and Cost

Pharmacologic: First Line Tx for Graves’ Disease

Question 8

Thioamides

What 4 are there/

Answer 8

1. PTU and Tapazole, Iodides, and Radioactive Iodine

Question 9

Thioamides

1. Tapazole (Methimazole) and PTU
   a. What do they do?
   b. What BLOCKS CONVERSION of T4 to T3?
   c. Gradual Effects?
2. Indications?
3. Adverse Effects?

Answer 9

1. a. Decrease Synthesis and Release of T4
   b. PTU blocks T4 to T3 conversion
   c. Circulating T3/T4 lasts a Week or so (Use B-Blockers)
2. ITCHING and SKIN RASH (most common)

BLACK BOX WARNING for PTU (SEVERE LIVER INJURY and ACUTE LIVER FAILER)

for this reason, TAPAZOLE (Methimazole) is DOC usually

Ganulocytopenia and Agranulocytosis (Reversible)

*Keep Dose LOW in Preggos (reduce Cretinisn and goiter in fetus)

Question 10

Iodide

1. How does it work?
2. How long does it last?
3. Indications?

Answer 10

1. DECREASES SYNTHESIS and Release of T4/T3 very quickly
2. Short Term: 6-8 wks
3. Decreases vascularity and thyroid content of gland…used for 7-10 days BEFORE SURGERY (can decrease likelihood of Thyroid Storm)

Question 11

Radioactive Iodine

1. Small Amts?
2. Lg Amts?
3. Indications
4. Adverse Effects

Answer 11

1. uCi = DIAGNOSTIC
2. mCi = DESTROYS GLAND
3. ELDERY Pts and peeps w/HEART DISEASE
4. usually causes Hypothyroidism over time. RISK of THYROID STORM (decrease risk by using THIOAMIDES (Not IODIDE!) Prior to Tx.

Question 12

Propanolol (B-Blocker)

1. How does it work?
2. Indication?
3. CI/Precautions?

Answer 12

1. RAPID DECREASE of many signs and symptoms of Hyperthyroidism
2. Used to prepare for surgery and while waiting for Thioamides or 131I to take Effect
3. CI in Pts w/OBSTRUCTIVE AIRWAY DISEASE or ASTHMA…may cause Bronchoconstriction!
   * You can use VERAPAMIL (Ca-Channel blocker) if Propanolol is CI.