<Li> The Na / I symporter transports two sodium ions across the basement membrane of the follicular cells along with an iodide ion . This is a secondary active transporter that utilises the concentration gradient of Na to move I against its concentration gradient . </Li> <Li> I is moved across the apical membrane into the colloid of the follicle . </Li> <Li> Thyroperoxidase oxidizes two I to form I. Iodide is non-reactive, and only the more reactive iodine is required for the next step . </Li> <Li> The thyroperoxidase iodinates the tyrosyl residues of the thyroglobulin within the colloid . The thyroglobulin was synthesised in the ER of the follicular cell and secreted into the colloid . </Li>

Which of the following is the primary effect of the thyroid hormones t3 and t4