Thyroid hormone modulates insulin-like growth factor-I(IGF-I) and IGF-binding protein-3, without mediation by growth hormone, in patients with autoimmune thyroid diseases.
The expression and synthesis of insulin-like growth factor-1 (IGF-I) and IGF-binding protein-3 (IGFBP-3) are regulated by various hormones and nutritional conditions. We evaluated the effects of thyroid hormones on serum levels of IGF-I and IGFBP-3 levels in patients with autoimmune thyroid diseases including 54 patients with Graves' disease and 17 patients with Hashimoto's thyroiditis, and in 32 healthy age-matched control subjects. Patients were subdivided into hyperthyroid, euthyroid and hypothyroid groups that were untreated, or were treated with methylmercaptoimidazole (MMI) or L-thyroxine (L-T4). Serum levels of growth hormone (GH), IGF-I and IGFBP-3 were determined by radioimmunoassay. Serum GH levels did not differ significantly between the hyperthyroid and the age-matched euthyroid patients with Graves' disease. The serum levels of IGF-I and IGFBP-3 showed a significant positive correlation in the patients (R=0.616, P<0.001). The levels of both IGF-I and IFGBP-3 were significantly higher in the hyperthyroid patients with Graves' disease or in those with Hashimoto's thyroiditis induced by excess L-T4 administration than in control subjects. Patients with hypothyroid Graves' disease induced by the excess administration of MMI showed significantly lower IGFBP-3 levels as compared to those in healthy controls (P<0.05). Levels of IGFBP-3, but not IGF-I levels, showed a significant positive correlation with the levels of free T4 and free T3. In Graves' disease, levels of TPOAb, but not of TRAb, showed a significant positive correlation with IGFBP-3. We conclude that in patients with autoimmune thyroid diseases, thyroid hormone modulates the synthesis and/or the secretion of IGF-I and IGFBP-3, and this function is not mediated by GH.
Inukai
T
T
Dept. of Medicine, Koshigaya Hospital, Dokkyo University School of Medicine, Japan.
Takanashi
K
K
Takebayashi
K
K
Fujiwara
Y
Y
Tayama
K
K
Takemura
Y
Y
D000328:Adult; D013956:Antithyroid Agents / Q000627:therapeutic use; D005260:Female; D006111:Graves Disease / Q000097:blood* / Q000188:drug therapy; D019382:Human Growth Hormone / Q000097:blood*; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D007564:Japan; D008297:Male; D008713:Methimazole / Q000627:therapeutic use*; D008875:Middle Aged; D012016:Reference Values; D012044:Regression Analysis; D013967:Thyroiditis, Autoimmune / Q000097:blood* / Q000188:drug therapy; D013974:Thyroxine / Q000627:therapeutic use*
D013956:Antithyroid Agents; D018972:Insulin-Like Growth Factor Binding Protein 3; D019382:Human Growth Hormone; D008713:Methimazole; D007334:Insulin-Like Growth Factor I; D013974:Thyroxine