NORMAL CALCITONIN RESPONSE TO PENTAGASTRIN STIMULATION IN PATIENTS WITH CHRONIC-RENAL-FAILURE

High calcitonin levels have been reported in chronic renal failure. To study the C cell response in patients with chronic renal failure, an intravenous bolus of pentagastrin was administered to 11 patients and 11 healthy subjects. Samples were obtained at 0, 1, 2, 3, 5 and 10 min for calcitonin assay. In order to detect only the active monomeric ca lcitonin, an immunoradiometric assay method was used. The influence of calcium, phosphate, alkaline phosphatase and intact parathyroid hormo ne was also evaluated. Although basal calcitonin levels were higher (p <0.01) in chronic renal failure (mean +/- SEM: 10.1 +/- 2.9 pmol/1) ve rsus healthy subjects (1.1 +/- 0.3 pmol/1), the area under the curve s howed there to be no differences between the two groups. The rising br anch of the area under the curve, employed as an expression of the C c ell response capacity, showed no differences either (chronic renal fai lure vs healthy subjects: 5.6 +/- 2 vs 2.6 +/- 0.7 pmol l-1 min-1, p = 0.28). In the chronic renal failure group, a positive correlation was found (r = 0.625, p < 0.05) between the rising branch of the area und er the curve and parathyroid hormone. We conclude that monomeric calci tonin is increased in chronic renal failure, but C cells of the thyroi d respond to pentagastrin, as they do in normal subjects. This finding is of great clinical importance when a patient with renal impairment is evaluated for medullary thyroid carcinoma. The calcitonin response to pentagastrin seems to be related directly to the degree of secondar y hyperparathyroidism in chronic renal failure.