Measurement of Serum Free IGF-1 in Diagnosis of Growth Hormone Deficiency
SUTTIPONG WACHARASINDHU, M.D., M.R.C.P. (UK)*, KA THAREE CHAICHANW ATANAKUL, B.Sc. **,
SUPAWADEE LIKITMASKUL,M.D.**,
KITTI ANGSUSINGHA,M.D.**
Affiliation : * Department of Pediatrics, Faculty of Medicine, Chulalongkom University. Bangkok 10330,
**Department of Pediatrics, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand.
AbstractSerum levels of total insulin-like growth factor-! (IGF-1) are growth hormone (GH)
dependent and can be used as the screening tool for GH deficient status. However, most of them
are bound to IGF-binding proteins, leaving less than 1 per cent in the free or unbound forms
which represent the active biological fractions. Serum free IGF-I levels were measured by
radioimmunoassay (IRMA) in 48 short children with various conditions. We found that the
means ± SEM of free IGF-I in children with panhypopituitarism (PAN) and complete growth
hormone deficiencies (cGHD) were significantly lower than those in sex and age matched
normal children (0.02 ± 0.01 vs 2.01 ± 0.7 ng/ml, p = 0.0006 and 0.42 ± 0.18 vs 1.72 ± 0.27 ng/ml,
p = 0.0007 respectively) but not in children with partial growth hormone deficiencies (pGHD)
(0.91 ± 0.3 vs 1.97 ± 0.4 ng/ml, p = 0.27) and idiopathic short stature (ISS) (0.94 ± 0.3 vs 1.95 ± 0.6
ng/ml, p = 0.13). However, when we classified the pGHD children into 2 groups according to
IGFBP-3 SDS for normal Thai children, we found that the mean of free IGF-I levels in pGHD
children with IGFBP-3 SDS ~ -1.3 was significantly lower than that of the controls. (0.68 ± 0.55
vs 2.66 ± 0.71 ng/ml, p = 0.04)
In conclusion, the measurement of free IGF-I level can be used to evaluate the GH status
of short children and might be used as a guide when starting treatment.
Keywords : Insulin-like Growth Factor-!
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