Growth hormone administration in older adults: effects on albumin synthesis

Evidence suggests that the albumin gene contains a growth hormone (GH) responsive element. Our purpose was to determine if GH administration to older men increases the rate of albumin synthesis and whether this is related to the increase in nitrogen retention observed during short-term recombinant human GH (rhGH) administration. Five older men (60-75 yr) received daily injections (40 micrograms/kg) of rhGH for 2 wk, whereas four others received daily injections (10 micrograms/kg) for 4 wk. In both the 2- and 4-wk recipients, rhGH administration increased (P < 0.05) fasting plasma insulin-like growth factor I levels and reduced (P < 0.05) 24-h urinary nitrogen excretion. However, during an overnight fast, the fractional rate of albumin synthesis determined by the in vivo rate of incorporation of intravenously infused L-[1-13C]leucine into plasma albumin was unchanged after 2 or 4 wk of treatment. The average plasma albumin fractional synthetic rate was 8.6 +/- 0.6%/day before and 9.4 +/- 0.7%/day after rhGH treatment (P = 0.12). We conclude that short-term rhGH administration and the subsequent increase in urinary nitrogen retention does not result in an increase in the rate of plasma albumin synthesis in older men.