Normal growth spurt and final height despite low levels of all forms of circulating insulin-like growth factor-I in a patient with acid-labile subunit deficiency.

In a recently described patient with acid-labile subunit (ALS) deficiency, the inability to form ternary complexes resulted in a marked reduction in circulating total insulin-like growth factor (IGF)-I, whereas skeletal growth was only marginally affected. To further study the role of circulating versus locally produced IGF-I in skeletal growth in this patient, we now describe in detail growth changes and their relationship with several components of the circulating IGF system. We followed growth and development up to the final height in a patient with complete ALS deficiency and determined both spontaneous and growth hormone (GH)-stimulated changes in the IGF system, including measurements of total, free and bioactive IGF-I, total IGF-II and insulin-like growth factor binding protein (IGFBP)-1, IGFBP-2 and IGFBP-3. The patient had a delayed growth and pubertal onset. Six months of GH treatment had no effect on growth. At the age of 19.3 years, he spontaneously completed puberty and had a normal growth spurt for a late adolescent (peak height velocity of 8.4 cm/year). A normal final height was attained at 21.3 years (167.5 cm; -0.78 SDS). During as well as after puberty, basal levels of total, free and bioactive IGF-I were low, as were total IGF-II, IGFBP-1, IGFBP-2 and IGFBP-3. GH treatment for 6 months normalized free IGF-I and increased bioactive IGF-I, but had no effect on growth velocity. This case story shows that in the presence of complete ALS deficiency, a height within normal limits can be obtained despite low levels of all forms of circulating IGF-I. Furthermore, the patient presented a delayed but normal growth spurt without any marked increment of circulating IGF-I. Copyright (c) 2007 S. Karger AG, Basel.