Follicular cell of the thyroid follicle secreting thyroid hormones, treatments. treatment of hyperthyroidism. Sectional view of follicular cells of the thyroid follicle in contact with a blood capillary (below). In cartridge, a thyroid follicle. Above, a silhouette locating the thyroid gland and the pituitary gland and the hypothalamus. The synthesis of thyroid hormones T3 and T4 which is carried out in the follicular cells and the colloid substance of the thyroid follicle, is stimulated by the TRH at the level of the hypothalamus, which induces the synthesis of TSH at the level of the pituitary gland.