Quantitative Evaluation by Immunocytochemistry of the Age-Related Variations in Thyroid C Cells in the Rat

C cells in the rat thyroid were identified easily and clearly using an immunocytochemical technique. This identification allowed a precise study to be carried out on the quantitative variations of these cells with respect to age (between 10 and 60 weeks) and sex of the animals. No difference related to sex was seen. There was a net increase in the volume fraction of C cells (hyperplasia) with age.