‘Surprising’ effect of growth hormone on BMI in normal-weight children

By Eleanor McDermid, Senior medwireNews Reporter

Researchers have found that the body mass index (BMI) standard deviation score (SDS) increases in normal-weight children receiving growth hormone (GH) treatment.

The effect, measured between starting treatment and attaining near adult height, was independent of indication for GH. The total cohort, which also included underweight and obese children, came from the KIGS (Pfizer International Growth Database) and comprised 2643 children with idiopathic GH deficiency (IGHD), 281 who were small for gestational age (SGA), 1661 girls with Turner syndrome and 142 children with Prader–Willi syndrome (PWS).

However, the researchers note that among normal-weight children with IGHD or Turner syndrome, GH dose negatively correlated with BMI-SDS change, with the highest doses associated with a BMI-SDS reduction. They say this argues against GH treatment having an adverse effect on BMI and further suggests that “normal weight children should be treated with an adequate dose of GH to avoid an inappropriate increase in BMI-SDS.”

Thomas Reinehr (Vestische Children's Hospital, Datteln, Germany) and colleagues also note that “[i]t is unclear whether the increase in BMI-SDS in normal weight GH-treated children reflects the natural course of BMI-SDS in healthy children or in the diseases themselves.” They say that more research is needed to determine if the weight increase affects fat mass, lean body mass or both.

Overall, normal-weight children had a BMI-SDS increase of between 0.22 and 0.85, depending on age and indication. Children who were underweight on commencing treatment all gained weight, with BMI-SDS increases of between 0.62 and 1.88, and there was a mixed pattern in overweight children. Those who were obese lost weight, with reductions ranging from 0.03 to 0.71.

Of note, underweight children who started treatment before the age of 8 years made greater weight gains than those who started later, while obese children tended to have larger BMI-SDS reductions if they started treatment before they were 8 years old, significantly so for those with IGHD.

Writing in Clinical Endocrinology, the researchers highlight that the average BMI-SDS reduction in obese children with PWS or IGHD, especially those who started treatment early, “was much greater than the reported effect of lifestyle interventions in obese children without PWS or IGHD”.

They say: “Therefore, early onset of GH therapy is not only necessary to improve height outcome, regardless of the indication, as demonstrated in this as well as in earlier studies, but also to achieve a normal weight status at [near adult height], especially when the child is underweight or obese.”

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