Acute effects of growth hormone administration: vitamin A and visceral protein concentrations

We determined albumin, total protein, somatomedin C, retinol binding protein (RBP), transferrin, prealbumin, and complement (C3) concentrations in serum, and vitamin A concentrations in plasma before initiation of growth hormone (GH) therapy and 13 h after each of 4 daily injections of GH (0.1 U/kg) in 6 GH deficient children. Levels of total protein, albumin, and transferrin did not change during the first week of GH administration, however, transferrin levels rose after 6 weeks of GH therapy. Initial somatomedin C levels were below the normal range (0.19 +/- 0.03 U/ml), and rose with GH administration in 4 of the 6 subjects, resulting in a post-treatment mean of 0.56 +/- 0.23 U/ml. With GH administration vitamin A and RBP concentrations decreased from initial values (P less than 0.05), and reached a plateau after 2 injections of GH, while there was no change in concentrations of other proteins. There was a significant linear correlation (P less than 0.05) between the levels of vitamin A and RBP before and after GH administration. We conclude that GH administration results in a selective and marked reduction in the concentrations of plasma vitamin A and serum RBP.