EFFECTS OF LOW-DOSE OF RECOMBINANT HUMAN GROWTH-HORMONE ON RENAL EXCRETION OF INSULIN-LIKE GROWTH-FACTOR-I (IGF-I) IN HUMANS - AN INVERSE RELATION BETWEEN SERUM AND URINARY IGF-I LEVEL

To elucidate the possible physiological interaction between growth hor mone (GH) and insulin-like growth factor-I (IGF-I) system in human kid ney, recombinant human GH (rhGH), which reached a supranormal level of serum GH, was administered, and serum and urinary IGF-I levels were d etermined in 6 normal men. The first two days served as a pre-control period (preTx). At days 3 and 4 (Tx), 2 U of rhGH was subcutaneously i njected twice at 8:00 AM and 8:00 PM. The following three days (days 5 , 6, 7) served as a post-control period (postTx). After rhGH administr ation, serum level of GH increased rapidly, followed by elevation of s erum IGF-I concentration. Changes in creatinine clearance during the s tudy were not significant. The 24-hour urinary IGF-I output decreased significantly during the rhGH administration period compared with that in pre- and post-Tx. During the Tx, urine volume and urinary excretio n of electrolytes decreased compared with those in preTx, and mostly r eturned to the preTx level during postTx. These results indicated an i nverse relationship between serum and urinary IGF-I level during the s upranormal elevation of serum GH, suggesting IGF-I accumulation within the kidney.