Circulating IGF-I levels in monitoring and predicting efficacy during long-term GH treatment of GH-deficient adults

Division of Endocrinology and Metabolism, University of Toronto, Canada.

OBJECTIVE: To investigate the effects of long-term GH in GH-deficient adults, as predicted by IGF-I levels. METHODS: Patients received GH, 5 microg/kg per day for 1 Month and 10 microg/kg per day for another 12-30 Months. Changes in body composition, cardiac structure/function, serum lipids and quality of life were measured. RESULTS: There was a significant increase in lean body mass (LBM) (2.21 kg; P<0.0001) after 6 Months, which was sustained throughout treatment. A larger increase occurred in males than females (2.97 vs 1.19 kg; P<0.0001). Total fat mass was reduced (2.56 kg; P<0.0001 (3.26 kg males, 1.63 kg females)). Responsiveness to GH varied greatly, but LBM changes correlated with IGF-I changes (P<0.004). Furthermore, thinner patients experienced greater and progressive LBM increases. There was an increase in ejection fraction (3.85+/-9.95%; P=0.0002) after 6 Months, sustained to 18 Months. These cardiac effects were equal for males and females, and did not correlate with IGF-I levels. Serum low-density lipoprotein/high-density lipoprotein ratios decreased within 6 Months, and were sustained thereafter. Quality of life improved significantly after 6 Months, an effect that was sustained/enhanced as treatment continued. No major adverse events were identified. CONCLUSIONS: Improved body composition is both reflected by IGF-I changes and predicted inversely by baseline adiposity. Other effects of GH replacement on cardiac function, dyslipidaemia and quality of life, however, do not correlate with circulating IGF-I concentrations. Our findings validate the importance of sustained GH therapy, but caution on the interpretation of IGF-I levels in monitoring the long-term effects of GH treatment.

This article has been cited by other articles:

				L. J. Woodhouse, A. Mukherjee, S. M. Shalet, and S. Ezzat The Influence of Growth Hormone Status on Physical Impairments, Functional Limitations, and Health-Related Quality of Life in Adults Endocr. Rev., May 1, 2006; 27(3): 287 - 317. [Abstract] [Full Text] [PDF]

				A. Mukherjee, J. E Adams, L. Smethurst, and S. M Shalet Interdependence of lean body mass and total body water, but not quality of life measures, during low dose GH replacement in GH-deficient adults Eur. J. Endocrinol., November 1, 2005; 153(5): 661 - 668. [Abstract] [Full Text] [PDF]

				C. L Boguszewski, L. H F Meister, D. C T Zaninelli, and R. B Radominski One year of GH replacement therapy with a fixed low-dose regimen improves body composition, bone mineral density and lipid profile of GH-deficient adults Eur. J. Endocrinol., January 1, 2005; 152(1): 67 - 75. [Abstract] [Full Text] [PDF]