Normal IGF-I and enhanced IGFBP-3 response to very low rhGH dose in patients with dilated cardiomyopathy

Well-nourished patients with dilated cardiomyopathy (DCM) show slight reduction of mean basal IGF-I levels which, however, display a response to a rhGH dose as low as 5.0 μg/kg/day similar to that of age-matched control subjects (CS). To further investigate peripheral GH sensitivity, we studied the IGF-I and IGFBP-3 responses to 4-day sc 2.5 μg/kg/day rhGH administration, the lowest effective dose able to increase IGF-I levels in normal subjects, in 10 DCM patients [age (mean±SE): 57.6±1.0 yr, body mass index (BMI): 24.0±1.2 kg/m2, left ventricular ejection fraction: 26.2±3.2%, NYHA (New York Heart Association): I/0, II/4, III/4, IV/2] and in 9 age-matched healthy CS (age: 55.3±1.2 yr, BMI: 23.7±1.8 kg/m2). Basal IGF-I levels in DCM were lower though not significantly than those in CS (147.7±9.8 vs 174.7±17.0 μg/l). Basal IGFBP-3 levels in DCM were similar to those in CS (3.1±0.3 vs 2.7±0.2 mg/l). In CS 4-day rhGH increased IGF-I levels (222.4±14.9 μg/l; p<0.01 vs baseline) but did not modify IGFBP-3 levels (3.0±0.2 mg/l). In DCM IGF-I levels were increased by 4-day rhGH administration (175.7±11.0 μg/l; p<0.05 vs baseline) with a similar percent extent than in CS. On the other hand, in DCM, but not in CS, 4-day rhGH significantly increased IGFBP-3 levels (3.5±0.3 mg/l; p<0.05 vs baseline). Therefore, in conclusion, testing with the lowest effective rhGH dose further suggest that peripheral GH sensitivity in well-nourished DCM is preserved. On the other hand, DCM patients show enhanced IGFBP-3 sensitivity to stimulation by rhGH.