Thyroparathyroid conditioning of hydrocortisone and glucagon-induced hypocalcemic effect in rats.

A single dose of 2.5 mg hydrocortisone induced hypocalcemia in both intact and parathyroidectomized rats. This effect disappeared in the thyroparathyroidectomized group and did not reappear after the substitution with parathormone. A single dose of 0.2 mg glucagon produced a significant hypocalcemic effect in intact, but not in parathyroidectomized rats. In the latter group, however, the hypocalcemic effect of glucagon reappeared after the administration of parathormone. It was concluded that the hypocalcemic effect of hydrocortisone may be conditioned by the presence of calcitonin secreting thyroid and that of glucagon - by the presence of parathyroids.