[Calcium-phosphate metabolism and bone markers in two patients with Noonan's syndrome treated with growth hormone].

Aim. To evaluate the possible effects of recombinant growth hormone (rhGH) therapy on mineral homeostasis and bone turnover, the authors studied calcium-phosphate metabolism parameters, including some bone markers, in 2 prepubertal subjects with Noonan's syndrome (NS). Methods. Two prebubertal males suffering from NS, short stature (-3.9 and -5.4 SDS respectively) and low growth velocity (3.9 and 3.3 cm/-year), were treated with rhGH (0.85 U/kg/week) for 1 year. Serum levels of total calcium (Ca), inorganic phosphate (P), magnesium (Mg), parathyroid hormone (PTH), calcitonin (CT), 250H vitamin D, 1.25(OH) 2 D, osteocalcin (BGP), type I procollagen carboxy-terminal propeptide (-PICP) and its telopeptide (ICTP) were measured. Results. The baseline values were in the normal range; during the treatment no remarkable difference in the values of every one parameters was detected in the 2 patients studied. In one of them, who responded to GH treatment with significantly improved growth velocity, serum levels of the BGP increased during the first semester, and then progressively declined; conversely, serum levels of the ICTP remained stable during the first 6 months of GH-therapy, whereas increased in the following 6 months. Conclusion. The results suggest that in Noonan's syndrome patients responding to GH-therapy, a stimulation of bone turnover, with ensuing increase of height velocity, takes place, at least during the first year of GH-therapy. The authors underline the necessity of confirming their results on a larger group of patients with Noonan's syndrome.