Growth hormone and IGF1 profile in short children with osteopetrosis

Osteopetrosis is commonly associated with short stature. To identify the cause, 8 children with osteopetrosis and short stature were studied. One showed evidence of renal tubular acidosis, none showed evidence of anaemia, and all were clinically and biochemically euthyroid. Growth hormone profile was assessed using night sampling (8 patients), growth hormone provocative testing using insulin-induced hypoglycaemia (6 patients), and L-dopa-propranolol (8 patients). The mean nocturnal growth hormone values taken at 60 and 90 min after onset of sleep and at 4 a.m. were 5.5, 12.8, and 11.5 mu/L respectively. The peak stimulated growth hormone mean values with the insulin-induced hypoglycaemia (glucose 1.6-3.0 mmol/L, mean = 2.2) was 14 mu/L (range 7.3-24.5 mu/L) and with the L-dopa-propranolol was 25.6 mu/L (range 12.3-49 mu/L). IGF1 levels taken at 0 and 120 min of insulin-induced hypoglycaemia (0 min for L-dopa-propranolol), and at 120 min of L-dopa-propranolol, showed normal values for age. We conclude that: (1) growth hormone profiles in these children are normal; (2) tissue unresponsiveness to growth hormone and/or IGF1 is not likely to be the cause of short stature in children with osteopetrosis; and (3) osteopetrosis per se is not an indication for assessment of growth hormone status.