Regulation of Calcitonin Secretion in Normal Man by Changes of Serum Calcium within the Physiologic Range

Abstract

A B S T R A C T To examine the relative importance of calcium and gastrin in regulation of calcitonin secretion, we administered graded oral doses of calcium to 10 normal men, ages 23-29 yr. Each subject had previously shown an appropriate increase in calcitonin secretion in response to a pharmacologic (0.5 ,ug/kg) pentagastrin injection. On separate days and in random order, each man drank 250 ml of distilled water containing 0.0, 0.5, 1.5, and 3.0 g of elemental calcium as the gluconate salt. Blood samples were drawn before and at 30, 60, 90, 120, 180, and 240 min after the oral calcium dose. The samples were analyzed for calcium by atomic absorption spectroscopy, and for gastrin and calcitonin by radioimmunoassays of established sensitivity and specificity. Ingestion of water (control) caused no change in any of the three variables. Calcium ingestion resulted in dose-related increases, within the normal range, of all three variables. Immunoreactive gastrin rose promptly, peaking at 30 min, and returning to basal levels or below by 120 min. In contrast, calcium and immunoreactive calcitonin levels rose slowly and in parallel, peaking at 120-240 min. Changes in calcitonin and changes in calcium were strongly and positively correlated, r = 0.73, when all data were pooled. Furthermore, individual linear regressions for changes in calcitonin and calcium levels (calculated separately for the three oral calcium doses in each subject) had positive slopes in 28 out of 30 sets (P < 0.01). The changes in calcitonin concentrations were much more poorly correlated with the corresponding changes in serum gastrin levels; in fact, the regression coefficient was weakly negative, r = -0.20. These results show that, at least in young adult men, changes of ambient calcium concentration within the normal range may be of

Epinephrine is a Hypophosphatemic Hormone in Man. PHYSIOLOGICAL EFFECTS OF CIRCULATING EPINEPHRINE ON PLASMA CALCIUM, MAGNESIUM, PHOSPHORUS, PARATHYROID HORMONE, AND CALCITONIN

“…iCT was measured with antiserum G-1701 by our previously published method (23). Earlier studies established the capacity of this assay to detect small changes in iCT concentrations (23)(24)(25)(26). We used our "microassay" modification for both assays to permit triplicate determinations with controls for nonspecific binding using only 200 ;J of plasma for each hormone (27).…”

Evidence that blood ionized calcium can regulate serum 1,25(OH)2D3 independently of parathyroid hormone and phosphorus in the rat.

“…Whether Ca"+ has the same effects in humans, how ionized calcium actually affects serum 1,25(OH)2D3, and whether Ca`+ has a strong regulatory effect when PTH is normal, rather than high, remain unanswered questions. Since transepithelial active transport of calcium by the intestine is regulated by 1,25(0Hh)D3 (39,40), an increase in the hormone augments calcium absorption and can thereby elevate the serum calcium level (41). Therefore, by directly regulating serum 1,25(OH)2D3, calcium appears to control its own absorption.…”

Long-Term Influence of Anticonvulsant Agents on Calcitonin, Parathyroid Hormone and Osteocalcin

“…Patients under anticonvulsant therapy (phenytoin and phénobarbital) were selected for this trial because this association of drugs induces more marked effects on calciotropic hormones [11], PTH values did not change in our patients when compared to controls and showed a negative correlation with CaC values, which was a physio logical condition [ 12], CT did not change either, and, as is the case under physiological conditions, there was a posi tive correlation with CaC [13], As in our case, although with a younger population group, Takesita et al [14] did neither observe PTH nor CT changes. Other authors, such as Weinstein et al [15], found decreased ionic calcium and increased PTH.…”