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Serum insulin-like growth factor 1 is associated with thyroid enlargement
The background of the study. Insulin-like growth factor 1 (IGF-1) is a hormone produced primarily in the liver that stimulates the growth of many tissues, and it may contribute to thyroid enlargement and the formation of thyroid nodules. To address this possibility, the relationships between serum IGF-1 concentrations and thyroid disorders were determined in healthy subjects.
How the study was done. The study group consisted of 3662 healthy subjects who participated in a population-based health survey in Germany. The demographic and clinical characteristics of the subjects were obtained by interview. Serum IGF-1 and thyrotropin (TSH) were measured, and thyroid volume and the presence of thyroid nodules >1 cm were determined by ultrasonography.
The results of the study. When divided into three groups, with serum IGF-1 values of <112, 112 to 156, and >156 ng/ml, both the women and men in the upper group were younger and had lower body-mass-index values than those in the lower group. The frequency of smoking was higher in the upper group in both women and men. Urinary iodine excretion, serum TSH concentrations, and the frequency of low serum TSH concentrations were similar in the women and men in each group.
The frequency of goiter was similar in the women and men in the three groups (35, 36, and 31 percent in women and 36, 42, and 37 percent in men). The frequency of thyroid nodules was lower in the women in the upper group (30, 22, and 16 percent) but not in the men (18, 18, and 14 percent).
In analyses adjusted for age, higher serum IGF-1 concentrations were associated with goiter in both women and men, thyroid nodules in men, and low serum TSH concentrations in women.
The conclusions of the study. Serum IGF-1 concentrations are slightly higher in women and men with goiter, in men with thyroid nodules, and in women with low serum TSH concentrations, suggesting that IGF-1 may contribute to thyroid enlargement.
The original article. Volzke H, Friedrich N, Schipf S, Haring R, Ludemann J, Nauck M, Dorr M, Brabant G, Wallaschofski H. Association between serum insulin-like growth factor-I levels and thyroid disorders in a population-based study. J Clin Endocrinol Metab 2007;92:4039-45.
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