SUSPENSION OF SEASONALTTY IN GROWTH VELOCITY DURING GROWTH HORMONE THERAPY IN SHORT CHILDREN

Abstract

We have previously shown a clear seasonality in growth velocity in prepubertal school children of normal height, both for height and lower leg length velocity (LLLV). The mechanisms behind seasonality is not known, thought previous studies have focused on seasonal changes of light as the synchronizing factor. It is not known if the hormones involved in the growth regulation are affected by the seasons. The aim of this study was to analyze seasonality in LLLV in children of short stature with spontaneous growth hormone (GH) secretion, before and during GH therapy. Twenty-seven short prepubertal children (19 boys and 8 girls; aged 4.9-12.6 years), with height SDS < −2 were followed one year prior to treatment, and during 18 months of GH therapy (0.1 U/kg-day). Lower leg length was measured using the Knemometer. The results show a clear seasonality in LLLV prior to GH treatment. The mean monthly LLLV before treatment was 1.81 cm/year (SD-0.25). During the spring-summer period the mean LLLV was 2.46 cm/year (SD=1.97) as compared to 1.88 cm/year (SD=0.63; p<0.001) during the autumn-winter. LLLV was 1.87 cm/year (SD=0.73) during the 3 months prior to GH-start and a significant increase (p<0.0001) was seen after the start of GH treatment giving a mean LLLV during the initial 3 months of 3.26 cm/year (SD=1.79). Seasonality in LLLV was not noted during the first 6 months of GH treatment. Further, between 6 and 18 months after start of GIH treatment, still no such seasonality could be noted comparing the summer-spring period (2.70 cm/year; SD=1.32) with the autumn-winter (2.71 cm/year; SD=1.05). The annual LLLV was 2.32 cm/year (SD=0.42) during this year on GH treatment. Despite of no clear seasonality in LLLV, during GH treatment, a large individual variation could be noted in short term growth. In conclusion, seasonality in LLLV was found in short children, as previously also been found in prepubertal school children of normal height. The seasonality pattern was, however, suspended during GH therapy, during 18 months of follow up.