Premium
Effect of thyroxine replacement on serum IGF‐I, IGFBP‐3 and the acid‐labile subunit in patients with hypothyroidism and hypopituitarism
Author(s) -
Schmid Christoph,
Zwimpfer Cornelia,
Brändle Michael,
Krayenbühl PierreAlexandre,
Zapf Jürgen,
Wiesli Peter
Publication year - 2006
Publication title -
clinical endocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.055
H-Index - 147
eISSN - 1365-2265
pISSN - 0300-0664
DOI - 10.1111/j.1365-2265.2006.02652.x
Subject(s) - medicine , hypopituitarism , endocrinology , western blot , chemistry , biochemistry , gene
Summary Objective To describe the effect of T4 replacement in patients with primary and central hypothyroidism on components of the IGF binding protein complex: IGF‐I, the acid‐labile subunit (ALS) and IGFBP‐3. Patients and methods We determined IGF‐I, ALS and IGFBP‐3 (by 125 I‐IGF‐II ligand blots and immunoblots) in serum of 19 patients with primary and 11 patients with central hypothyroidism. Results Mean (± SD) free T4 (fT4) increased from 4·4 ± 2·4 pmol/l at baseline to 18·6 ± 5·2 pmol/l following T4 therapy. In patients with primary hypothyroidism, IGF‐I concentrations increased from 101 ± 57 to 158 ± 60 µg/l ( P < 0·001) and ALS from 12·6 ± 4·7 to 15·6 ± 5·2 mg/l ( P = 0·001). IGFBP‐3 levels (in arbitrary units, AU), assessed by 125 I‐IGF‐II ligand blot and by Western blot (the intensity of the 45/42‐kDa doublet following T4 replacement defined as 1 AU) increased from 0·74 ± 0·47 to 1 ( P = 0·029) and from 0·76 ± 0·42 to 1 ( P = 0·018), respectively. In patients with hypopituitarism, IGF‐I and ALS concentrations increased on T4 therapy from 49 ± 23 to 97 ± 36 µg/l ( P < 0·001) and from 7·8 ± 4·1 to 11·0 ± 2·7 mg/l ( P = 0·010), respectively. IGFBP‐3 remained unchanged during T4 replacement. Conclusions T4 replacement increases the serum levels of IGF‐I and ALS in patients with primary as well as central hypothyroidism. IGFBP‐3 levels increase in response to T4 replacement in patients with primary hypothyroidism but not in those with central hypothyroidism, suggesting that thyroid hormones increase IGF‐I and ALS but not IGFBP‐3 in patients with GH deficiency.