Endocrine Abstracts

Background: One of the main effects of growth hormone therapy (rhGH) in the adult GH deficient patient (AGHD) is to positively modify body composition, with a reduction in fat mass (BF) and an increase in total lean mass (LM). However, the response to replacement therapy is highly variable and, contrary to what described in children, the potential predictive factors are not yet known.

Aim of the study: To assess the impact of basal IGF-I levels on variations of body composition induced by rhGH therapy (median dose 0.2 mg/day) in AGHD.

Study protocol: A monocentric longitudinal prospective study in 44 patients (age at diagnosis 46.1 ± 11 years) with GHD of different aetiology (17 NFPA, 7 craniopharyngiomas, 4 prolactinomas, 4 acromagaly, 2 Cushing diseases, 1 TSH pituitary adenoma, 3 empty sella, 1 Rathke’s cleft cysts, 2 hypophysitis, 2 idiopathic, 1 post-traumatic). Patients have been divided into two groups based on theIGF-I basal levels: Group A with IGF-I > –2 SDS (n = 15, 8 M) and group B with IGF < –2 SDS (n = 29, 13 M). Body composition evaluated with dual-energy X-ray absorptiometry and IGF-I levels were assessed at 12 months (n = 44, 21 M), 3–5 years (n = 40, 19 M), and 7–10 years (n = 29, 11 M).

Results: At baseline, no differences were observed between the two groups except for BF %, higher in group B. In the short term, BF % decreased in both groups (from 33 ± 7% to 30 ± 7% group A and from 38 ± 7% to 36 ± 8% in group B, P < 0.05), however, this reduction remained significant in the medium and long term only in group B (35 ± 8% and 37 ± 9%, P = 0.002 and 0.04 vs baseline, respectively). Nevertheless, in both groups, BF% showed an increase at last follow up. Instead, LM showed a sustained increase in both groups and at all times of observation. The IGF-I SDS levels as well as the rhGH dose did not differ between the two groups in the short, medium and long term.

Conclusions: basal IGF-I levels can be predictive of the effect of rhGH therapy on BF %, suggesting greater efficacy in patients with more severe deficiency. The relative increase in BF % observed in the long term still leaves open the question on the parameters to be used in order to define the optimal timing of stopping rhGH therapy in AGHD.