Colloid Between the follicles are located small groups of parafollicular cells which secrete hormone thyrocalcitonin or often called just calcitonin Calcitonin functions to reduce calcium levels in Follicular cells the blood by actively reducing breakdown of bone and inhibiting re absorption of calcium in Blood Blood digestive system capillary ParafollicularBetween the follicles are located small groups of parafollicular cells which secrete hormone thyrocalcitonin or often called just calcitonin. Calcitonin functions to reduce calcium levels in the blood by actively reducing breakdown of bone and inhibiting re￾absorption of calcium in digestive system