Can FT4 help with blood sugar?

FT4 (free thyroxine) is a thyroid hormone primarily used to treat hypothyroidism. There is a known link between thyroid function and glucose metabolism: untreated hypothyroidism can reduce insulin sensitivity and negatively affect blood sugar. In such cases, FT4 supplementation can normalize metabolism and indirectly improve glycemic control. However, in euthyroid (healthy thyroid) individuals, there is no evidence that FT4 lowers blood sugar or helps with diabetes. On the contrary, overdosing thyroid hormones can cause hyperthyroidism, which raises blood sugar and increases the risk of cardiac arrhythmias. The evidence level is therefore 'mixed/unclear': moderate clinical data exist for hypothyroid patients, but none for healthy individuals. MyBody-X tests do not measure thyroid levels; FT4 should only be taken under medical supervision. Caveat: self-medication with thyroid hormones is dangerous.