October 14, 2015
Metformin Appears to Slightly Increase Height in Young Users

Alberta, Canada—A new Canadian study has discovered an unexpected side effect of prescribing metformin to children and adolescents: a slight increase in height.

The article published online by JAMA Pediatrics notes the increased off-label use of metformin in nonadults for polycystic ovary syndrome as well as impaired glucose tolerance, nonalcoholic fatty liver disease, and obesity. The authors, from the University of Alberta, reviewed the medical literature to find that the widely prescribed diabetes medication might be associated with a small increase in height in children and adolescents in randomized clinical trials providing the largest cumulative metformin doses.

Researchers included 10 studies with a total of 562 children and adolescents at baseline. Of those, 330 were female, with the average age varying from nearly 8 to 16, the average body mass index (BMI) ranging from 18.4 to 41, and usage varying from 3 to 48 months.

While height changes were not significantly different between metformin users and control group participants in the overall studies, further analyses stratified according to the cumulative metformin dose in milligrams per day times the number of days of treatment indicated about a one-centimeter increase in height with metformin use. That was the case only in the five studies providing the largest cumulative metformin doses and not in the five studies providing the lowest doses compared with the control group, study authors emphasize.

Background information in the article points out that previous meta-analyses have identified a large variability in the effects of metformin use on BMI, but apparently have not considered height changes as a confounder.

The researchers say they weren’t always able to obtain height data from many of the studies but suggest their preliminary finding could be significant.

“While an approximate 1-cm increase in height may appear small, it is likely underestimated given that many studies were of short duration and included older adolescents, potentially after epiphyseal growth plate closure,” study authors conclude. “Our results also suggest a need for additional longer-term studies in younger participants because preliminary evidence suggests that these individuals may experience greater increases in height compared with a control group.”
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