Short stature: new challenges in growth hormone therapy

Prediction of height velocity of prepubertal children with growth hormone deficiency in the first year of treatment with recombinant human growth hormone

AIM

Several methods have been developed to predict the outcome of growth hormone (GH) therapy in children with growth hormone deficiency (GHD).

METHODS

Over 50 factors for each of 92 prepubertal patients with GHD (26 patients with total and 45 patients with partial GHD, 21 patients with neurosecretory dysfunction) were collected and included in multiple regression analyses and other nonlinear models to predict height velocity (HV) (cm/yr) in the first year of treatment. Afterwards the model was validated by two other cohorts of patients from other universities, which followed the same treatment regime as our clinic.

RESULTS

Twelve parameters had a significant correlation to HV (p<0.05) and a coefficient of determination >20%. Two parameters (In BA, In GHmax) showed a coefficient of determination >60% for children with GHD in multiple regression analysis. The validation of the mathematical model against another data set showed different results. GH was measured by the same method, but BA was scored at the first clinic as in our clinic by only one doctor and in the other university by several radiologists. The accuracy of prediction in the first clinic was significantly higher than in the other university.

CONCLUSION

This model demonstrates that exact scoring of BA and precise measurement of GHmax in the stimulation test is necessary, and if carried out carefully leads to useful prediction values for determining height velocity.

Effects of exogenous growth hormone on skeletal muscle of young female rats

We examined the effects of exogenous growth hormone (GH) treatment on the soleus and rectus femoris muscles of young female rats. Rat GH (1.8 IU/mg) was administered for 3 weeks by subcutaneous injection, twice a day, at doses of 0.5, 0.6, and 0.8 mg/day during the 1st, 2nd and 3rd week, respectively. Final body weight, as well as wet and dry weight, of the soleus and rectus femoris muscles were significantly greater in the GH-treated group, compared to controls. Muscle weight to body weight ratios did not differ between the two groups. The fiber type composition of the soleus muscle was determined by histochemical staining for myosin ATPase activity. No statistically significant difference was found between the GH-treated and the control groups in the percentages of fiber types. However, GH treatment significantly increased the cross-sectional area of type II fibers of the soleus muscle. These results suggest that, in young female rats, acceleration of body weight gain by homologous GH administration is accompanied by a proportional hypertrophy of skeletal muscle mass. Increased muscle mass is due to hypertrophy of muscle fibers. Type II muscle fibers appear to be more sensitive to GH stimulation.