Calcitonin was extracted from surgically-derived prostate tissue, and quantified using radioimmunoassay. Normal prostatic specimens contained 15.18 ± 10.03 ng./gm. wet weight (mean ± S.D., n = 20), with a range of 1.50 to 39.62 ng./gm. The result for the hyperplastic tissue samples (n = 20) averaged 0.63 ± 0.39 ng./gm. with a range of 0.22 to 1.49 ng./gm. This difference was statistically significant (p < .0001). Dilution profiles for the prostatic calcitonin and synthetic monomeric human calcitonin were congruent, suggesting that the two peptides are identical. A comparison of calcitonin levels and the number of immunohistochemically derived neuroendocrine cells in contiguous tissue sections showed an empiric correlation. The mean calcitonin level in normal human prostate tissue was found to exceed values previously reported for numerous other organs, with the exception of the thyroid gland, the principal source of circulating calcitonin. We propose that a subpopulation of neuroendocrine cells within the prostate gland produce calcitonin, as is the case in the gastrointestinal tract, lung, and other organs. Our findings also support the hypothesis that the calcitonin found in seminal fluid originates in the prostate. Putative roles for calcitonin in the genitourinary system are discussed.
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