<prompt> After thyroidectomy for medullary carcinoma of thyroid, which is impoant for determining recurrence of tumour: September 2009ThyroglobulinTSHCarcinoembryonic antigenThyroxine levels  <response>: As. C: Carcinoembryonic antigenUnlike papillary and follicular thyroid cancers which arise from thyroid hormone producing cells, medullary cancer of the thyroid originates from the parafollicular cells also called C cells of the thyroid.These C cells make a different hormone called calcitonin.High levels of serum calcitonin and carcinoembryonic antigen are produced by many medullary tumours.Levels falls after resection and rise again with recurrence making it a valuable tumour marker in the follow-up of patients with this diseaseThis cancer has a much lower cure rate than does the well differentiated thyroid cancers papillary and follicular, but cure rates are higher than they are for anaplastic thyroid cancer. 