Insulin-, Glucagon- and Calcitonin-Induced Early Decrease in Serum Calcium

Abstract

Early effects of insulin, glucagon and calcitonin on serum calcium were studied in clinical patients as well as in Wistar rats. Average serum calcium was reduced by 0.44, 0.64, 0.72 and 0.37 mg/100 ml (P < 0.01, < 0.001, < 0.001 and < 0.001 resp.) in 12 non-diabetic and by 0.47, 0-63, 0.58 and 0.32 mg/100 ml (P < 0.001 for all) in 25 diabetic patients at the 5th, 10th, 15th and 20th min following subcutaneous administration of 0.5 U/kg bw insulin (Actrapid NOVO). Similar decrease in serum calcium (0.45 mg/100 ml, P < 0.01) was observed in the rat at the 10th min after insulin injection. 1 mg glucagon (Ely Lilly) given subcutaneously to 11 human subjects resulted in 0.38, 0.63, 0.63 and 0.42 mg/100 ml decrements in serum calcium (P < 0.001, < 0.001, < 0.001 and < 0.01 resp.) at the 5th, 10th, 15th and 20th min. In the rat calcitonin administration decreased serum calcium significantly, however, at the time intervals employed this early decrease could not be differentiated from the well-known hypocalcaemic effect of this hormone. Both the alterations of blood glucose after insulin and of blood glucose and IRI after glucagon were preceded by changes in serum calcium. On the analogy of literature data about parathormone action, this early hypocalcaemic effect of insulin, glucagon and calcitonin may be due to activation of target cells by these hormones. 1 Supported in part by the Scientific Research Council, Ministry of Health, Hungary (1-22-0320-03-1/H).