Endocrine Abstracts

Introduction: Adult growth hormone deficiency (AGHD) is associated with lower bone mass and likely with increased risk of fragility fractures. GH replacement leads to increase in bone mineral density (BMD) and trabecular bone score (TBS). The effect of adequate levels of vitamin D during GH replacement is important to provide effect on TBS.

Aim: To assess long–term effectof recombinant GH replacement on BMD and TBS with regards to vitamin D levels during period of 8 years.

Patients & Methods: Prospective follow-up of AGHD patients at one single center. Allpatients with adult GHD followed at single center. All participants were replaced with daily injection ofrecombinant human (rh) GH in IGF-1 normalizing regimen according to Endocrine Society Guidelines. From total number of 63 patients, 31 patients ended 8 years follow-up period with BMD measurement [at lumbar spine (L-spine) and total hip (TH)] and TBS performed at year 8. Deficiencies of other pituitary axes were treated if necessary. All patients were supplemented with 800 IU /day of cholecalciferol and 1000–1200 mg/day of calcium as recommended by International Osteoporosis Foundation. The study cohort was divided based on 25(OH)D levels into two groups with the cutoff defined as the median at each time-point of follow up.

Results: Study group consisted of 16 males and 15 females (14 with adult onset (AO) /17 with childhood onset (CO); mean age at diagnosis 25.03 yrs) AGHD patients. Average dose of rhGH was 0.4 mg/day and after six month of treatment IGF1 levels stayed in reference range (±2 SDs for age). After 8 years of GH replacement, increase of 8.7% and 8.2% (both P < 0.05) for LS and TH BMD but not TBS was observed. TBS decrease of 2,2% in patients with 25(OH)D levels below median (24.1 mg/l) and slight increase +0,8% (P = 0.05) in group with 25(OH)D levels above median was observed. BMD in both groups increased similarly.

Conclusion: Long-term GH replacement in adult GHD led to increase in BMD, but not TBS. However, after adjustment for vitamin D levels, patients with vitamin D below median showed significant decrease in TBS but no difference in BMD at both sites. In addition slight TBS increase was observed in patients with vitamin D above median. This study has shown that adequate vitamin D levels in GH-replaced have beneficial effect on bone quality, as measured by TBS.