One year of insulin-like growth factor I treatment does not affect bone density, body composition, or psychological measures in postmenopausal women

The activity of the hypothalamic-GH-insulin-like growth factor I (hypothala mic-GH IGF-I) axis declines with age, and some of the catabolic changes of aging have been attributed to the somato-pause. The purpose of this investi gation was to determine the impact of 1 yr of IGF-I hormone replacement the rapy on body composition, bone density, and psychological parameters in hea lthy, nonobese, postmenopausal women over 60 yr of age. Subjects (n = 16, 7 0.6 +/- 2.0 yr, 71.8 +/- 2.8 kg) were randomly assigned to either the self- injection IGF-I (15 mug/kg twice daily) or placebo group and were studied a t baseline, at 6 months, and at 1 yr of treatment. There were no significan t differences between the IGF-I and placebo groups in any of the measured v ariables at baseline. Fasting blood IGF-I levels were significantly elevate d above baseline values (65.6 +/- 11.9 ng/mL) at 6 months (330.0 +/- 52.8) and 12 months (297.7 +/- 40.8) in the IGF-I treated group but did not chang e in the placebo subjects. Circulating levels of IGF-binding protein-1 and -3 were unaffected by the IGF-I treatment. Bone mineral density of the fore arm, lumbar spine, hip, and whole body [as measured by dual-energy x-ray ab sorptiometry (DXA)] did not change in either group. Similarly, there was no difference in DXA- measured lean mass, fat mass, or percent body fat throu ghout the treatment intervention. Muscle strength values (grip, bench press , leg press), blood lipid parameters (cholesterol, high-density lipoprotein , low-density lipoprotein, triglycerides), and measures of postmeal glucose disposal were not altered by IGF-I treatment, although postmeal insulin le vels were lower in the IGF-I subjects at 12 months. IGF-I did not affect bo ne turnover markers (osteocalcin and type I collagen N-teleopeptide), but s ubjects who were taking estrogen had significantly lower turnover markers t han subjects who were not on estrogen at baseline, 6 months, and 12 months. Finally, the psychological measures of mood and memory were also not alter ed by the intervention. Despite the initial intent to recruit additional su bjects, the study was discontinued after 16 subjects completed the protocol , because the preliminary analyses above indicated that no changes were occ urring in any outcome variables, regardless of treatment regimen. Therefore , we conclude that 1 yr of IGF-I treatment, at a dose sufficient to elevate circulating IGF-I to young normal values, is not an effective means to alt er body composition or blood parameters nor improve bone density, strength, mood, or memory in older women.