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Insulin‐like growth factor binding protein‐3 proteolysis and growth of athyreotic infants in the first weeks of life
Author(s) -
Zamboni G,
Antoniazzi F,
Tatò L
Publication year - 2000
Publication title -
acta pædiatrica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.772
H-Index - 115
eISSN - 1651-2227
pISSN - 0803-5253
DOI - 10.1111/j.1651-2227.2000.tb03349.x
Subject(s) - medicine , endocrinology , proteolysis , insulin like growth factor binding protein , insulin like growth factor , growth factor , growth hormone , hormone , receptor , enzyme , biochemistry , biology
To gain a better understanding of the growth of athyreotic newborns in the first weeks of life, we evaluated auxological parameters and determined the serum levels of growth hormone (GH), insulin‐like growth factor I (IGF‐I) and free IGF‐I, and IGF‐binding protein‐3 (IGFBP‐3) in 15 hypothyroid infants (10 females) at a mean age of 25 d of life, immediately before the beginning of L‐thyroxine therapy, and at 3 and 6 mo of life. Fourteen normal infants (9 females) of the same age were studied as controls. IGFBP‐3 proteolytic activity was evaluated in 8 patients and in 8 controls at 25 d and 6 mo of life. There was no significant difference concerning weight and length between the patients and controls at birth, 25 d, 3 and 6 mo of life. The blood GH, IGF‐I and IGFBP‐3 levels were significantly lower in patients at diagnosis than in controls of the same age ( p < 0.01 for all parameters), as well as IGFBP‐3 studied by Western blotting. At diagnosis, the patients’free IGF‐I level was within the control range, but the free IGF‐I percentage of total IGF‐I was higher than in the controls ( p , < 0.01). IGFBP‐3 proteolytic activity was found to be greater in the patients ( p < 0.01). At 6 mo of life, after therapy, none of these parameters was different from those of the controls. Conclusion : Increased IGFBP‐3 proteolytic activity in our patients at diagnosis, favouring IGF‐I bioavailability, could account for normal free IGF‐I levels and in turn for their normal growth pattern during the first weeks of life and before the start of treatment.