This study deals with the setting up of human serurn calcitonin radioimmunoassay (hCT-RIA) using the high titer and specific antibody which was prepared by our own laboratory. Thefinal dilutfon of the antibedy titer was 1: 1 200 000 when the binding rate of Bo/T was 3o%.The anthay’s affinity constant (Kd) was 2. 25 X 1O11L/M. No cross reaction was found be-tween the antithey and the folfowing eight different peptide hormones and proteins, viz.: TSH,T3, T4, ACTH, PTH, BGP, Insulin and Gastrin. The coefficients variation of intra and interassay were 3. 2% and 9. 0%, respectively. The mean recovery rate of CT was 99. 8%. The sen-sitivity bf this assay was 9. 4 pg/ml. The examination of this methodology showed that an its in-dices met the demands of RIA. There was no difference in the mean value of serum CT betweenthe two sexs in 232 normal subjects, but the serum CT concentration in those aged of sixty andover of men and women, were much lower than those aged of fourty group. Mean CT concentra-tbo was low in the patients with primary osteoporosis, but were significantly higher in those suffering from medullary thyroid carcinoma, primary hyperparathyroidism crisis and chronic renalfailure.
