<prompt> The density of the parafollicular cells or C- cells in the thyroid gland is maximum at the:IsthmusPosterior paJuncture of the upper ? and lower 23 of the glandUpper ? of the gland  <response>: The parafollicular cells or C- cells in the thyroid gland is present in all pas of the thyroid gland. Their density is greatest in the juncture of the upper one-third and lower two-thirds of the gland. Ref: Harrison, E-18, P-2912 