Evaluation of free insulin-like growth factor-I measurement on the diagnosis and follow-up treatment of growth hormone-deficient adult patients.
OBJECTIVE
Insulin-like growth factor (IGF-I) and IGF binding protein-3 (IGFBP-3) are GH-dependent and their concentrations have been used in the diagnosis of GH deficiency. Recently, the free fraction of IGF-I has received more attention. The aim of the study was to assess the role of free IGF-I in the diagnosis of GH deficiency in adults, and in follow-up during treatment with recombinant human GH (rhGH).


METHODS
We studied 24 adult patients with pituitary disease and GH deficiency and 25 matched controls. Nine patients were re-evaluated after 6 months of treatment with rhGH (0.25 U/kg/week).


METHODS
Serum levels of IGF-I, free IGF-I, IGFBP-3 and IGFBP-1 were measured by immunoradiometric assay.


RESULTS
Serum free IGF-I levels were significantly lower in the GH deficient group than in the normal group (mean: 0.84 and 1.32 micrograms/l respectively, P = 0.0009). Furthermore, serum IGF-I levels were also lower (mean: 92.24 and 230.47 micrograms/l respectively, P < 0.0001). 63% of patients had serum IGF-I concentration below the normal range. For free IGF-I, 52% of the GH deficient patients showed levels below the lowest value obtained for the normal group. Seventy-five percent of the patients showed at least one of the two determinations below the normal range. The free-total IGF-I ratio was significantly higher (P = 0.025) in GH deficient group (range: 0.19-21.29, mean: 2.53) than in normal controls (range: 0.2-2.15, mean: 0.6). Regarding IGFBP-3 and IGFBP-1 no differences were observed between the two groups. During rhGH treatment the increase in serum total and free IGF-I and IGFBP-3 paralleled the beneficial effects on body composition.


CONCLUSIONS
Free IGF-I may be another useful method for the diagnosis of GH deficiency, particularly if related to total IGF-I concentration.
Musolino
N R
NR
Unidade de Neuroendocrinologia, Hospital das Clinicas, São Paulo, Brazil.
Da Cunha Neto
M B
MB
Marino Júnior
R
R
Giannella-Neto
D
D
Bronstein
M D
MD
D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood; D001823:Body Composition; D015992:Body Mass Index; D016022:Case-Control Studies; D004734:Energy Metabolism; D005260:Female; D005500:Follow-Up Studies; D013006:Growth Hormone / Q000172:deficiency* / Q000627:therapeutic use; D020249:Hormone Replacement Therapy; D006801:Humans; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000097:blood; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D008297:Male; D008875:Middle Aged; D010900:Pituitary Diseases / Q000097:blood* / Q000188:drug therapy / Q000378:metabolism; D011237:Predictive Value of Tests
D015415:Biomarkers; D018970:Insulin-Like Growth Factor Binding Protein 1; D018972:Insulin-Like Growth Factor Binding Protein 3; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone