Several anesthetics, but not diethyl ether, cause marked elevation of serum parathyroid hormone concentration in rats.

The effects of anesthetics on serum parathyroid hormone (PTH) concentrations were determined by a new homologous two-site immunoradiometric assay for rat PTH. Serum PTH concentrations (mean ± SE) from ether-anesthetized rats (14.7 ± 1.5 pg/ml, n = 22) were not significantly different from those of decapitated unanesthetized female rats (13.0 ± 1.8 pg/ml, n = 21). Serum PTH concentrations in pg/ml (n = 4-14) for other anesthetics tested were : ketamine, 12.5 ± 1.1 ; Na pentobarbital, 23.3 ± 2.4 ; methoxyflurane (inhalation), 42.2 ± 6.8 ; and xylazine combined with ketamine, 51.4 ± 113 pg/ml. The latter two concentrations were significantly (p < 0.001) higher than the values for all other anesthetics and decapitation. Elevation of serum PTH induced by pentobarbital or ketamine + xylazine increased with time under anesthesia. Neither serum Ca 2+ concentrations nor pH differed among any of the groups. We conclude that anesthesia induced by pentobarbital, methoxyflurane, or ketamine + xylazine in rats leads to a marked elevation of serum PTH levels that appears to be related to the duration of anesthesia and not due to any measurable fall in serum Ca 2+ .