P. Iglesias et al., Serum insulin-like growth factor type 1, insulin-like growth factor-binding protein-1, and insulin-like growth factor-binding protein-3 concentrations in patients with thyroid dysfunction, THYROID, 11(11), 2001, pp. 1043-1048
Thyroid hormones play a role in the regulation of insulin-like growth facto
r type 1 (IGF-1) and insulin-like growth factor-binding protein-3 (IGFBP-3)
expression, and both IGF-1 and IGFBPs have been shown to be related to the
function and growth of the thyroid. Our aim was to evaluate serum concentr
ations of IGF-1, IGFBP-1, and IGFBP-3 in patients with thyroid dysfunction
before and after normalization of thyroid function. The study was performed
in 86 patients with thyroid dysfunction (43 hyperthyroid and 43 hypothyroi
d. patients) and 17 euthyroid subjects. Serum growth hormone (GH), insulin,
IGF-1, IGFBP-1, and IGFBP-3 were measured in all patients before and after
normalizing serum thyroid hormone concentrations. Hyperthyroid patients sh
owed IGF-1 (198.8 +/- 17.0 mug/L) and IGFBP-3 levels (4.2 +/- 0.2 mg/L) sim
ilar to those found in the control group (217.9 +/- 20.3 mug/L and 4.2 +/-
0.3 mg/L, respectively). After therapy these levels significantly decreased
to 156.6 +/- 11.1 mug/L (p < 0.01) and 3.3 +/- 0.1 mg/L (p < 0.001), respe
ctively. IGFBP-1 concentrations were clearly higher than those found in con
trols (22.7 +/- 2.6 vs. 5.7 +/- 1.5 mug/L, p < 0.001) and exhibited a signi
ficant reduction after therapy for thyroid hyperfunction (11.0 +/- 1.7 mug/
L, p < 0.001). Patients with hypothyroidism showed serum concentrations of
IGF-1 (161.5 +/- 13.1 mug/L, p < 0.05) and IGFBP-3 (3.2 +/- 0.3 mug/L, p <
0.05) significantly lower than those found in healthy volunteers. However,
replacement therapy with levothyroxine did not induce any significant modif
ication of these concentrations (152.6 +/- 10.6 mug/L and 3.2 +/- 0.2 mg/L,
respectively). Similarly, patients with thyroid hypofunction exhibited rai
sed levels of IGFBP-1 (15.5 +/- 0.9 mug/L, p < 0.05 vs. control group) that
were significantly decreased after therapy (8.8 <plus/minus> 1.4 mug/L, p
< 0.01). The results of the present study show that thyroid status affects
GH/IGF axis. Hypothyroidism is associated with significant reductions of IG
F-1 and IGFBP-3, and IGFBP-1 is elevated in both hypothyroidism and hyperth
yroidism.