Tox: Thyroid Hormone

Question 1

Formulations of thyroid hormone

Answer 1

1) Synthroid -> T4
2) Tri-iodothyronine -> T3
3) Liotrix -> T3+T4
4) Natural desiccated animal thyroid -> T3+T4

Question 2

Timing of onset of symptoms after Synthroid overdose and why

Answer 2

Delayed by 2-5 days.

T4 requires in vivo conversion to the active hormone T3.

Question 3

Timing of onset of symptoms after T3 overdose

Answer 3

Produce symptoms within 6hrs post ingestion.

Question 4

Symptoms of thyroid hormone OD

Answer 4

Tremor, confusion, agitation, hyperreflexia.
Tachycardia, HTN, palpitations, diaphoresis, flushing, diarrhea, mydriasis.
Fever, wt loss, heat intolerance if chronic overdose.

Question 5

Treatment of thyroid hormone OD

Answer 5

1) AC if within 1-2hrs large acute ingestion
2) Benzos for agitation
3) BB (e.g. propranolol or esmolol) to control severe tachydysrhythmias.
4) Agents that block endogenous thyroid hormone production have LIMITED UTILITY!!