29- What is idiopathic short stature?
Idiopathic short stature (ISS) is defined as height 2SD below the mean for age
and gender of corresponding population without any evidence of chronic sys-
temic illness or chromosomal, psychosocial, or endocrine disorders. ISS is a
heterogeneous disorder and is predominantly contributed by children with
familial short stature (FSS) and constitutional delay in growth and puberty
(CDGP). However, some children with ISS neither qualify for the diagnosis of
CDGP nor for FSS. GH response to provocative stimuli is essentially normal
in children with ISS; however, serum IGF1 levels are variable. The likely
abnormalities in children with ISS include reduced integrated GH secretion,
defect in GH molecule or its receptor, impaired IGF1 post-receptor signaling,
SHOX haploinsufficiency, or defective chondrocyte growth and proliferation
(Fig. 1.14).Fig. 1.13 Intrinsic short
stature due to
achondroplasia in siblings
1 Disorders of Growth and Development: Clinical Perspectives