Can lamotrigine (lamictal) affect tsh levels? also, what do low tsh mean (if t3 (liothyronine) and t4 are normal)?

Not alot: Thyroid interaction is not common with Lamictal, however as with all medications for each individual that can be a possibility. As to your low TSH that is usually a resonse to elevated T3, (liothyronine) T4. Remember that there can be variations in your thyroid measurements from one time to another. How do you feel. Do you have thyoid symptoms: cold, tired, fatigued, skin or nail changes?