The effect of growth hormone replacement therapy for up to 12 months on lipoprotein composition and lipoprotein(a) in growth hormone-deficient adults

The effect of growth hormone replacement therapy in near physiological doses on lipoprotein composition and serum lipoprotein(a) concentrations was investigated in growth hormone-deficient subjects. A randomised, double-blind, placebo-controlled trial of recombinant growth hormone was undertaken for 6 months followed by an open extension for a further 6 months (0.125 IU/kg per week for the first 4 weeks of each 6 month period and thereafter 0.25 IU/kg per week). A total of 18 patients with isolated growth hormone deficiency or hypopituitarism were studied. Lipid concentrations were estimated in lipoprotein fractions and protein concentrations were measured in low density lipoprotein (LDL). Glucose and glycated haemoglobin in blood and insulin, cholesterol, triglyceride, apolipoproteins A-I and B and lipoprotein(a) concentrations were measured in serum. In the placebo-controlled phase fasting blood glucose concentrations increased with growth hormone treatment from 5.0±0.2 to 5.8±0.2 mmol/l (P=0.02) (mean±S.E.M.), although no significant changes were seen in lipids or lipoproteins. In the group receiving active treatment total serum cholesterol decreased from 6.0±0.4 to 5.2±0.3 mmol/l (P=0.002) after 6 months, due to reduced LDL cholesterol concentrations. Low density lipoprotein protein concentrations fell (0.8±0.1 versus 0.7±0.1 g/l) (P=0.005), and LDL phospholipid levels decreased from 0.9±0.1 to 0.7±0.1 mmol/l (P=0.007). Serum cholesterol and LDL composition reverted to pre-treatment values by 12 months. Fasting blood glucose remained above pre-treatment values (P=0.036) and fasting insulin was significantly increased (P=0.044). There was no effect of growth hormone therapy on serum triglyceride, apolipoprotein or lipoprotein(a) concentrations. In conclusion, growth hormone therapy with near physiological doses has no long term effects on serum lipoprotein(a) concentrations or lipoprotein composition.