Final answer:
The follicle cells of the thyroid gland produce thyroglobulin, which is used to synthesize the thyroid hormones thyroxine (T4) and triiodothyronine (T3), critical for metabolic regulation.
Step-by-step explanation:
The substance produced by follicle cells of the thyroid gland is thyroglobulin. This glycoprotein is secreted into the colloid of the thyroid follicles where it serves as a precursor for the synthesis of the thyroid hormones thyroxine (T4) and triiodothyronine (T3). These hormones are essential for regulating the basal metabolism and are released upon stimulation by the thyroid-stimulating hormone (TSH) from the anterior pituitary. Although calcitonin is another hormone related to the thyroid gland, it is specifically produced by the parafollicular cells, or C cells, not the follicular cells. Calcitonin functions to lower blood calcium levels and promote bone growth.