Cessation of growth hormone (GH) results in loss of lean body mass and reduced accrual of bone mass in adolescents with severe GH deficiency- 2 year follow up
PV Carroll, WM Drake, KT Maher, K Metcalfe, MO Savage, DB Dunger, NJ Shaw, C Camacho-Hubner & JP Monson
Continuation of GH at final height in hypopituitary adolescents with severe GH-deficiency results in accrual of bone mass over 12 months. We report body composition and BMD in 7 of these patients who discontinued GH but continued to have observations over 24 months. Five males and 2 females were included (17.4plus/minus0.3, years, meanplus/minusSE), in this Ethics Commitee approved study. All had severe GH-deficiency with multiple pituitary hormone deficits on appropriate replacement. Measurements of serum IGF-I and whole-body dual energy X-ray absorptiometry (DXA) were performed at baseline (height velocity less than2 centimetres per year) while all patients were on GH and thereafter at 6 monthly intervals over 2 years. Serum IGF-I decreased following GH cessation (226plus/minus48 vs 110plus/minus20 vs 105plus/minus31, nanograms per millilitre, baseline vs 1 year (pless than0.01) vs 2 years (pless than0.01). A progressive reduction in lean body mass occurred (38.2plus/minus3.4 vs 36.5plus/minus3.2 vs 36.1plus/minus3.2, kilograms, baseline vs 1 year (pless than0.01) vs 2 years (pless than0.01), whereas no change was recorded in whole-body fat mass (19.8plus/minus3.5 vs 20.3plus/minus4.2, kilograms, baseline vs 2 years). Total body bone mineral content remained unchanged (2218plus/minus96 vs 2181plus/minus130 vs 2199plus/minus117, grams, baseline vs 1 year vs 2 years) however there was a gradual improvement in lumbar spine T score (minus1.88plus/minus0.20 vs minus1.63plus/minus0.22, baseline vs 2 years (pless than0.01)).
The baseline T scores indicate that these adolescents had not yet achieved peak bone mass. Cessation of GH replacement at completion of longitudinal growth resulted in loss of lean body mass and virtual arrest of bone mineralisation over 24 months. As skeletal maturation and changes in body composition may continue after completion of linear growth these preliminary data provide evidence that GH may have important effects during the period between completion of linear growth and full maturation. Further studies will confirm whether cessation of GH in the hypopituitary adolescent has adverse effects on BMD in adult life.