BMI gains in early childhood tied to premature adrenarche in CF boys

Study suggests recommended feeding regimens may need to be reevaluated

Andrea Lobo, PhD avatar

by Andrea Lobo, PhD |

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A mother and young son walk hand in hand in front of a rising sun.

A greater increase in body mass index (BMI), a measure of body fat, from ages 1 through 6 in boys with cystic fibrosis (CF) results in the early production of sex hormones, called adrenarche, according to a small study.

Boys with early adrenarche had an accelerated bone age, which may affect their final height.

“High calorie feeding regimens may need to be reconsidered, especially in early childhood in boys, as it may result in a too rapid BMI gain and potentially resulting in a decreased final height,” the researchers wrote in  “BMI increase during early childhood in boys with cystic fibrosis and early adrenarche,” which was published in Pediatric Pulmonology.

CF is caused by mutations in the CFTR gene that lead to abnormally thick, sticky mucus accumulating, which leads to a range of symptoms. These include digestive problems that influence nutritional intake and affect being able to maintain a healthy weight. Maintaining a proper weight and gaining weight is important for children with CF.

Studies have indicated a faster BMI increase between ages 1 and 6 may be associated with a lower final height in boys with CF, however.

Here, researchers in the Netherlands analyzed the frequency of early adrenarche — when sex hormones start being produced before age 9 and cause body changes like pubic hair, acne, and adult-type body odor — in 13 boys with CF, between ages 8 and 9, to see if it is associated with a significant change in BMI between ages 1 and 6. The boys mean age was 8.6 and they had annual CF checkups at a children’s hospital.

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 Link between early adrenarche, BMI change

At age 1, data were available for 11 boys with normal weight. All but one (who was overweight) maintained normal weight at age 6.

Eight boys had early adrenarche before they were 9, as measured by a rise in dehydroepiandrosterone sulfate (DHEAS) levels equal to or higher than 1 micromole (umol)/L. DHEAS, which is produced in the adrenal glands, is a precursor of sex hormones like testosterone.

The variation in BMI z-scores during early childhood (ages 1 to 6) was significantly higher among boys with early adrenarche compared to those with lower DHEAS. BMI takes into account a person’s weight and height; BMI z-scores are measures of BMI adjusted for a child’s age and sex that reflect the difference to reference values in a healthy population.

A greater increase in BMI z-scores in early childhood was significantly associated with higher DHEAS levels. No such correlation with DHEAS levels was seen with BMI and weight z-scores at the time of the DHEAS evaluation.

“In conclusion, significant BMI Z‐score increase in early childhood (between 1 and 6) results in (too) early adrenarche in boys with CF,” the researchers wrote.

Bone age was assessed based on an X-ray of the left hand and was accelerated in five boys with early adrenarche. No such accleleration was seen in six boys without it.

“The fact that significant early BMI Z‐score increase in young boys with CF may result in decreased final height due to early adrenarche should be taken into account when deciding on the feeding regimen in new young boys with CF,” wrote the scientists, who noted the study’s small sample size and short follow-up time, with no patient having reached his final height, were limitations of their study. Future research should confirm these associations in a larger number of patients and study these possible correlations in girls with CF, they said. “We also recommend future studies to focus on reevaluating the current recommended feeding regimens in children with CF, balancing between ensuring sufficient calorie intake necessary for the underlying disease and avoiding excessive calorie intake and thereby causing a too rapid BMI gain.”