Thyroid hormones
- Replace deficient thyroid hormone
- Levothyroxine (T4) is standard therapy
- Liothyronine (T3) acts faster/shorter
- TSH usually guides primary-hypothyroid dosing
- Iron/calcium reduce levothyroxine absorption
- Excess dosing → AF, bone loss + anxiety
- Routine T3 combination therapy is uncommon
Class at a glance
- Replace deficient thyroid hormone
Practical pearls
- Levothyroxine (T4) is standard therapy
Other practical pearls
- Liothyronine (T3) acts faster/shorter
- TSH usually guides primary-hypothyroid dosing
Members / distinctions
- Iron/calcium reduce levothyroxine absorption
- Excess dosing → AF, bone loss + anxiety
- Routine T3 combination therapy is uncommon
Pearls
- T4/T3 combination no better on average; some patients prefer it
- If combining, use T4:T3 ratio about 13–20:1
Self-check
- Which test usually guides primary-hypothyroid dosing?
TSH. - What reduces levothyroxine absorption?
Iron and calcium.
Drugs in this class (3)
Thyroid hormones prescription history
Animated chart of estimated U.S. prescriptions per year, Thyroid meds (1893–2026).
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