During puberty there is an acceleration in the rate of linear growth in both sexes associated with an increase in secretion of GH and IGF1. Previously we have shown that both T and DHT affected growth to about the same extent though the two treatments had opposite effects on plasma GH levels. Hence, we studied the effect of sex hormones on the GH-IGF1 system of 21 males (age 12.4-16.9 yrs) with constitutional delay of growth and adolescence, at Tanner stage I-II of puberty. Stimulated GH response was >10 ng/ml in all subjects. Each subject was studied before and after 2.5-3.5 months of treatment with 80-125mg/m2/month of either T or DHT. Samples for ICGH were collected overnight for 12 hour, where as the other samples were drawn early morning. Table

Table 1

Growth velocity over 12 weeks was the same in both the groups. There was a significant increase in all the GH-IGF1 parameters in the T group and a decrease in the DHT group. Only the change in ICGH was statistically significant. Hence T and DHT have opposing effects on GH but similar effects on growth. This suggests that the acceleration of growth at the time of puberty is independent of circulating levels of GH and IGF1 or its binding proteins. It is possible that androgens increase the effect of IGF1 in cartilage.