‘Primary IGF1 deficiency (IGFD)’ is defined by low levels of IGF1 without a concomitant impairment in GH secretion in the absence of secondary cause. The aims of this study were to evaluate the prevalence of non-GH deficient IGFD in prepubertal children with isolated short stature (SS) and to describe this population.
This retrospective study included all children with isolated SS seen in our Pediatric Endocrinology Unit from January 2005 to December 2007. Children were included based on the following criteria: i) SS with current height SDS ≤ −2.5, ii) age≥2 years, and iii) prepubertal status. Exclusion criteria were: i) identified cause of SS and ii) current or past therapy with rhGH. IGF1-deficient children were defined as children without GH deficiency and with IGF1 levels below or equal to −2 SDS.
Among 65 children with isolated SS, 13 (20%) had low IGF1 levels, consistent with a diagnosis of primary IGFD, four of which were born small for gestational age and nine were born appropriate for gestational age. When compared with non-IGFD children, IGFD children had higher birth weight (−0.7 vs −1 SDS, P=0.02) and birth height (−1.7 vs −2 SDS, P=0.04) and more delayed bone age (2.6 vs 1.7 years, P=0.03).
The prevalence of primary IGFD was 20% in children with isolated SS. Concerning the pathophysiology, our study emphasizes that IGFD in some children may be secondary to nutritional deficiency or to maturational delay.