medwireNews: A cohort study of healthy infants has characterised the relationships between circulating levels of insulin-like growth factor (IGF)-I and IGF binding protein (IGFBP)-3 and changes in body length and weight in the first year of life.
The investigators collated information for 119 boys and 114 girls participating in the COPENHAGEN Minipuberty Study, all of whom were born appropriate for gestational age (AGA) and with a birth weight standard deviation (SD) score of between – 2 and 2 SD.
Overall, 186 of the children attended the clinic six times between 0 and 12 months of age, say Emmie Upners and colleagues, from Copenhagen University Hospital – Rigshospitalet in Denmark.
“We provide detailed reference curves based on longitudinal data for IGF-I and IGFBP-3 during infancy” for both boys and girls, the team reports in The Journal of Clinical Endocrinology & Metabolism.
The individual mean length velocity for each child was stable during the first year, while weight velocity slowed, the researchers say.
At birth, girls had higher levels of IGF-I than boys, but boys had an increase in this biomarker over the first 10 days of life. This was followed by an IGF-I plateau around 6 months of age in both sexes, with comparable IGF-I levels at 12 months.
“Notably, this pattern closely resembled the shape of the length and weight velocity curves”, comment Upners and co-authors.
However, further analysis indicated that mean IGF-I was significantly associated with mean weight velocity in girls but not boys.
And the relationship between IGF-I and weight velocity did not change when also considering body fat, “suggesting that the association […] was not primarily mediated through gain in fat mass”, the researchers observe.
Girls also had higher levels of IGFBP-3 at birth than boys; both sexes had an increase in concentrations over the first 10 days of life followed by stable IGFBP-3 levels over the first year of life. There was a “strong correlation” between IGFBP-3 and IGF-I, as well as a significant and positive relationship found between the IGFBP-3 and mean weight velocity, but not height velocity.
Acknowledging earlier research showing a correlation between variants of the PAPPA2 gene encoding for IGF-I bioavailability and height, the team also assessed for a relationship between PAPPA2 genotype and height in the children.
The researchers did not find a significant correlation between any of the three PAPPAS2 genotypes and mean length velocity or mean weight velocity, but admit that their “sample size is probably too small to detect statistically significant effect sizes of a single genetic variant.”
By Lynda Williams
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