Endocrine Abstracts

Background: Insulin-like growth factor 1 (IGF1) has molecular structure similar to insulin. As an important mediator of growth hormone, IGF-1 plays roles in growth of children and anabolic effects of adults. We evaluate serum levels of IGF-1 in patients with hyperthyroidism or euthyroidism.

Subjects and methods: In this study, 30 patients with hyperthyroidism (HY group) and 30 euthyroid individuals (EU group) were recruited. The patients of HY group were treated with anti-thyroid regimens as clinically indicated, whereas no medication was given to EU group. The demographic characteristics, anthropometric and laboratory data of both groups at baseline and at the 6th month were compared. Associations between levels of IGF1 and free thyroxine (fT4), TSH, or log transformation of TSH (logTSH) were analyzed.

Results: At baseline, the HY group had significantly higher serum IGF1 levels than the EU group (median (Q1, Q3): 305.4 (257.4, 368.1) vs 236.7 (184.6, 318.8) ng/ml, P<0.01). The serum IGF-1 levels of the HY group decreased after anti-thyroid regimens, but still were higher than that of the EU group at the 6th month (299.5 (249.9, 397.9) vs 222.1 (190.2, 305.4) ng/ml, P<0.01). At the baseline, the serum levels of IGF1 in all patients were positively associated with fT4 (β=29.02, P<0.01) and negatively associated with TSH (β=−31.46, P=0.04). The associations between serum levels of IGF1 with fT4 or TSH became insignificant at the 6th month. However, the serum IGF1 levels were persistently negatively associated with logTSH both at baseline (β=−29.04, P<0.01) and at the 6th month (β=−26.65, P=0.02).

Conclusions: In comparison to EU group, patients with hyperthyroidism had higher serum IGF1 levels, which decreased after anti-thyroid regimens. The serum IGF1 concentrations were negatively associated with logTSH in patients with hyperthyroidism or euthyroidism.