A COMPARISON OF THE EFFECT OF TSH, GH AND PROLACTIN ON THE RENAL IODIDE EXCRETION IN UNRESTRAINED RABBITS

The immediate effect of graded iv doses of heterologous TSH, GH and prolactin on the renal iodide excretion was sutdied in unrestrained rabbits with implanted Geiger Müller detectors. Both TSH and GH lowered the fractional excretion rate of iodide. The duration of the effect was significantly correlated to the magnitude of the administered dose. The lowest dose with a significant effect was 10-20 mU TSH and 50 mU GH. Prolactin had no similar effect even in high pharmacological doses. An effect similar to that of small TSH doses was recorded following administration of 20-40 microng TRH iv. The immediate effect of GH on the iodide excretion accords with previous reports about similar effect on sodium excretion and suggests, that the effect of GH and TSH on the iodide excretion is secondary to a general effect on kidney function. The demonstration, that the effect is present in unrestrained animals after administration of physiological doses indicates, that the effect is not only of pharmacological significance, but may also have physiological significance.