Why thyroglobulin level are not elevated in thyrotoxicosis fictitious

Why thyroglobulin level are not elevated in thyrotoxicosis fictitious and they are elevate in all other causes of hyperthyroidism ?

Endo v/s exo

Endogenously produced T3/T4 are stored as Thyroglobulin in the thyroid.

Thyrotoxicosis Factita means exogenous intake of T3/T4. Thyroglobulin doesn’t rise because there is no excess production by the gland.