* Since 1972 * Dietary Supplement * Iodine w/Thyroxin Free Thyroid, Thymus & Spleen Concentrates Tri-40 was formulated because kinesiological testing reveals that the thymus and spleen work synergistically with the thyroid. Kelp is added as a natural source of iodine. This product has been produced in a facility that is NSF GMP Registered.