The current systematic review demonstrates the thyroid-stimulating properties of olive derivatives, including olive oil, olive leaf extract, and olive residues like pomace and solid pulp, which increase the concentrations of thyroid hormones (mainly T3) in euthyroid animals [67,68,69,70] and animals under heat stress- [71,72,73] or with chemically-induced hypothyroidism [74,75]. This evidence concerns the gene TG and hypothyroidism.