medwireNews: Very young children with Prader–Willi syndrome continue to accrue mental and motor development benefits during 3 years of treatment with growth hormone (GH), say researchers.

Stephany Donze (Dutch Growth Research Foundation, Rotterdam) and colleagues previously found that 1 year of GH treatment improved these outcomes in a randomised trial with untreated patients as the comparator group.

In their latest study, they show that mental and motor development continued to improve over 3 years of treatment in 35 boys and 28 girls with Prader–Willi syndrome who were a median age of 1 year when they started on GH.

The team notes that they “cannot exclude that part of this increase may be explained by spontaneous improvement of hypotonia with age and early start of physical therapy” but stresses that “it would be unethical to withhold GH for 3 years, knowing the positive effects of GH on numerous outcomes in children with [Prader–Willi syndrome]”, making a randomised trial unfeasible.

At baseline, the patients’ mental and motor development, measured on the Bayley Scales of Infant Development II, was an average of 58.1% and 41.9%, respectively, of that expected for their age. There were large variations between individuals, however, from 24% to 91% for mental development and 15% to 78% for motor development.

Mental and motor development improved to 65.7% and 54.8%, respectively, of that expected during the first year of GH treatment and to 79.6% and 78.2% over the subsequent 2 years of treatment, although patients’ development remained significantly below the average for their age.

These improvements were not affected by whether patients were male or female or whether they had a deletion or a maternal uniparental disomy, and they were not associated with changes in head circumference, height standard deviation score or lean body mass.

However, the researchers found that age at GH initiation did influence mental and motor development, with earlier initiation associated with larger improvements, “suggesting that starting GH treatment early, in a critical period of neurodevelopment, could enhance psychomotor and cognitive development [in] the longer term”.

In light of this finding, it is now their clinical practice to start GH treatment as young as possible in patients with Prader–Willi syndrome, they say.

The team’s findings are published in The Journal of Clinical Endocrinology & Metabolism.

By Eleanor McDermid

J Clin Endocrinol Metab 2018; doi:10.1210/jc.2018-00687

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