Regular doses of a hormone may help to boost cognitive skills in people with Down’s syndrome, a pilot study has suggested.
Researchers fitted seven men who have Down’s syndrome with a pump that provided a dose of GnRH, a gonadotropin-releasing hormone, every two hours for six months.
Six out of the seven men showed moderate cognitive improvements after the treatment, including in attention and being able to understand instructions, compared with a control group who were not given the hormone.
However, experts raised concerns about the methods used in the study, urging caution over the findings.
The team behind the work said brain scans of the participants, who were aged between 20 and 37, given the hormone suggest they underwent changes in neural connectivity in areas involved in cognition.
“[People] with Down’s syndrome have cognitive decline which starts in the 30s,” said Prof Nelly Pitteloud, co-author of the study from the University of Lausanne. “I think if we can delay that, this would be great, if the therapy is well tolerated [and] without side effects.”
Writing in the journal Science, Pitteloud and colleagues said they previously found mice with an extra copy of chromosome 16 experienced an age-related decline in cognition and sense of smell, similar to that seen in people with Down’s syndrome – who have an extra copy of chromosome 21.
In a series of experiments, the team found regular doses of gonadotropin-releasing hormone boosted both the sense of smell and cognitive performance of these mice.
Pitteloud said no side effects were seen in the participants and that the hormone is already used to induce puberty in patients with certain disorders.
“I think these data are of course very exciting, but we have to remain cautious,” said Pitteloud. She said larger, randomised control studies are now needed to confirm that the improvements were not driven by patients becoming less stressed during assessments and thus performing better.
Prof Michael Thomas of Birkbeck, University of London, who studies cognitive development across the lifespan in Down’s syndrome, said the results were exciting.
“For parents, this is good news: interventions can still yield benefits across the lifespan,” he said, although he noted it is not clear how applicable the hormone therapy would be for children.
However Prof Andre Strydom, a specialist in the psychiatry of intellectual disabilities at King’s College London, said the mice used in the study are no longer considered a good model for Down’s syndrome as their extra chromosome contains several different genes to those present on chromosome 21 in humans.
Elizabeth Fisher, professor of neurogenetics at the UCL Queen Square Institute of Neurology, added those differences meant it is unclear if cognitive and olfactory decline in the mice had the same cause as similar traits in people with Down’s syndrome.
Strydom also cautioned that the pilot study was very small with participants aware of the treatment they were receiving, while the assessment used for cognitive performance is not generally thought to be suitable for people with Down’s syndrome. “The cognitive outcomes are not convincing at all,” he said.
Defending the work, Pitteloud said the similarities in cognitive decline and loss of smell between the mice and people with Down’s syndrome meant – while imperfect – the mouse model is useful.
While Strydom said efforts to improve difficulties experienced by people with Down’s syndrome are welcome, the pilot study findings need to be replicated in other work. “There is a long way to go before one could offer it in clinic,” he said.
