[Need of thyroxine in chronic effects of growth hormone (GH) on phosphorus and calcium metabolism of female adult rat (author's transl)].

The object of the present work was to determine the part played by thyroxine (T4) in chronic effects of GH on phosphocalcium metabolism. Therefore, we used hypophysectomized-thyroparathyroidectomized female rats. The results were that: 1. Repeated daily administration of GH to female rats which had been operated on was not followed by the hyperphosphatemia classically observed in normal animals. GH always decreased urinary calcium and phosphorus excretion, indicating a direct renal effect of this hormone, irrespective of blood variations in the ions. 2. Chronic administration of infra-physiological doses of L-thyroxine (0.25 mug/100 g per day) enabled one again to obtain in operated rats the increase of phosphatemia specifically due to GH. 3. With the doses of GH and thyroxine used in these experiments, the blood calcium level of rats which have been operated on decreased. In conclusion, GH intervenes directly in phosphocalcium metabolism and it helps maintain a high phosphatemia. Thyroxine permits this last mentioned effect.