Endocrine Abstracts

JOINT1496

Objective: High normal IGF-1 levels may be associated with more favourable outcomes of long-term growth hormone replacement therapy (GHRT) in adult growth hormone deficiency (AGHD). However, the distinctive effects of maintaining the upper (0-2 SDS) vs lower normal (-2-0 SDS) range of IGF-1 SDS in AGHD remain largely understudied.

Methods: We conducted a cross-sectional study with 31 patients with AGHD receiving GHRT with daily GH > 5 years and 2-year mean IGF-1 between -2 to +2 SDS range. Patients were categorized according to their 2-year mean IGF-1 SDS into the upper or lower normal IGF-1 range. Clinical characteristics, anthropometric parameters assessed by dual-energy X-ray absorptiometry, laboratory tests, intima-media thickness (IMT) and reactive hyperemia index (RHI) were evaluated. Associations of those parameters with the mean IGF-1 SDS range over 2 and 5 years were explored.

Results: Over the 2-year period, 18 patients (58. 1 %) had mean IGF-1 SDS in the upper and 13 in the lower normal range. Long-term maintenance of upper normal IGF-1 SDS was more frequent in man than women (72. 2 % vs. 27. 8 %; P = 0. 024) and in patients with longer GHRT duration (median GHRT duration (25–75 % range): 28 years (16. 5–35) in higher normal group vs. 15 years (5–20) in lower normal; P = 0. 033). Patients with tumour-related AGHD had a lower 5-year mean IGF-1 SDS than patients with non-tumour etiology. Long-term maintenance of IGF-1 SDS in the higher normal range was associated with lower high-sensitivity C-reactive protein (hs-CRP) levels (median (25–75 % range): 0. 8 (0. 6-1. 1) vs. 1. 8 (0. 8-4. 6); P = 0. 005) and lower body fat percentage (median (25–75 % range): (30. 1 % (25. 2-34. 8) vs. 39. 5 % (32. 2-44. 0); P = 0. 008). A negative correlation was identified between hs-CRP and the 5-year mean IGF-1 SDS (r = -0. 705, p < 0. 001). The IGF-1 SDS range was not associated with IMT, RHI, glucose metabolism or lipid profile.

Conclusion: Long-term maintenance in the upper normal IGF-1 SDS was more frequent in male than female patients with AGHD. The upper normal range was associated with lower marker of low-grade inflammation and lower body fat percentage. Prospective randomized studies are needed to evaluate the long-term and sex-specific effects of targeting higher vs. lower normal IGF-1 SDS range in AGHD, for both, daily and weekly GHRT.