By Eleanor McDermid, Senior medwireNews Reporter
Spontaneous catch-up growth after birth in short children who were born small for gestational age (SGA) is a negative predictor of their long-term response to growth hormone (GH) treatment, say researchers.
Judith Renes (Erasmus Medical Center - Sophia Children’s Hospital, Rotterdam, the Netherlands) and team had expected that children with a greater spontaneous catch-up growth after birth would have the largest responses to GH, but found the reverse to be true, after accounting for gestational age, birth length and birth weight standard deviation score (SDS).
“One explanation might be that a greater spontaneous catch-up growth results in a height closer to [target height], possibly reducing the potential for response to GH”, they write in Clinical Endocrinology.
Indeed, spontaneous catch-up growth after birth correlated positively with adult height, despite its negative association with response to GH.
The 170 SGA patients in the study had a height SDS for their calendar age of –2 or below, and started GH treatment (1 mg/m2 per day) at a median age of 7.1 years. The 30% of children who were shorter than 140 cm at puberty onset received gonadotrophin releasing hormone analogue to delay puberty while they continued to take GH. This group attained a similar adult height to those who were 140 cm or higher at puberty onset.
Starting GH at a younger age was associated with a larger treatment response; however, most children’s growth decelerated during puberty, meaning that their final adult height was less than had been predicted at the onset of puberty. On average the height SDS fell by 0.4 in boys and 0.5 in girls, but being younger at GH initiation increased the likelihood of growth deceleration during puberty.
The SGA children overall entered puberty slightly later than average, but had a “moderately advanced” bone age at puberty onset. “These findings together might contribute to the early growth deceleration occurring from mid-puberty”, say the researchers. They note that other research suggests the phenomenon “seems to be related to SGA”.
They add: “Our findings show that the height SD score before the onset of puberty is not a reliable predictor of [adult height], and physicians should therefore be careful in extrapolating prepubertal SD scores to predict [adult height] because this can result in an overestimation of [adult height].”
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