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 microg/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 s.c. 2.5 microg/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 microg/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 microg/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 microg/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.