Abstract
The distinctive effects of maintaining the upper- (0-2) versus lower-normal (-2-0) range of IGF-1 SDS in adult growth hormone deficiency (AGHD) remain understudied. We conducted a cross-sectional study on 31 patients with AGHD receiving growth hormone replacement therapy (GHRT) with daily GH for >5 years, with a 2-year mean IGF-1 SDS ranging between -2 and +2. Patients were categorized into the upper- or lower-normal range IGF-1 SDS groups according to their 2-year mean. Associations of clinical characteristics, anthropometric parameters, laboratory tests, and vascular markers of subclinical atherosclerosis with the 2-year IGF-1 SDS range and 5-year mean IGF-1 SDS were explored. Long-term maintenance of upper-normal IGF-1 SDSs was more common in men and in patients with a longer duration of GHRT. Patients with tumor-related AGHD had a lower 5-year mean IGF-1 SDS. Long-term maintenance of IGF-1 SDS in the upper-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). Moreover, a negative correlation was identified between a hs-CRP and the 5-year mean IGF-1 SDS. The association between the upper-normal IGF-1 SDS range and lower body fat percentage lost significance after adjusting for sex, due to the higher proportion of male patients in the upper-normal IGF-1 SDS group. In conclusion, long-term maintenance of upper-normal IGF-1 SDSs was associated with male sex and reduced low-grade inflammation. Randomized controlled studies are needed to evaluate the long-term and sex-specific effects of targeting the upper- vs. lower-normal IGF-1 range in AGHD.