Thyroid T3 (Cytomel)
Neurohormone
- Treatment resistant depression
- Use T4 for hypothyroidism, T3 for depression
- Bipolar Depression
Features
Dosing
Triiodothyronine 25 mcg qd x1 wk then 50 mcg qd x 1 wk. If no response at 50 mcg, raise by 25 mcg/wk to max of 150 mcg qd. Lower dose if tachycardia (> 100 bpm).
Management
The theory is that in depression (particularly bipolar) the cells are unable to absorb T3, so TSH and T3 levels may be normal but still need more.
Triiodothyronine (T3) is the preferred thyroid med for antidep augmentation (better than T4 because it goes into CNS quicker and has shorter half-life so may work faster). Use T4 to treat hypothyroidism however (T4 is converted to T3 so covers both).
Caution in people with heart disease, hypertension, arrhythmias. Also warning of low bone mineral density (so best to use 6 mth if possible then wean off). Check thyroid labs as that is routine, but actually don’t dose based on the labs dose based on symptoms. If signs of hyperthyroidism (tachycardia >100 bpm, anxiety, hot sweats, headache, tremor, restlessness), lower down.
EMR Text
Depression
Triiodothyronine use based on randomized controlled trials in major depressive disorder.
Risks of supraphysiologic thyroid, including osteopenia and arrhythmias, reviewed with patient.
Bipolar
Triiodothyronine use based on randomized controlled trials in treatment-resistant bipolar disorder, where it improved depression and rapid cycling.
Risks of supraphysiologic thyroid, including osteopenia and arrhythmias, reviewed with patient.