Age-associated C-cell hyperplasia in the human thyroid.

C cells in 26 normal human thyroids from forensic autopsies were identified by immunoperoxidase staining for calcitonin. C-cell concentrations and total C-cell numbers were determined with the use of morphometric techniques. There was great variation in C-cell density within a given gland and among individuals, although C cells tended to concentrate about one third of the way down the vertical axis of the lateral lobes. Densities of 1-2000 cells/cu mm were found in the third and later decades. In addition there was a statistically significant (P less than 0.01) positive Spearman correlation between total C-cell numbers and age in males. C-cell hyperplasia appears to be an age-related phenomenon that may have physiologic significance and must be taken into consideration in evaluation of thyroid glands for the diagnosis of premalignant lesions of C cells.