ECE2013 Poster Presentations Thyroid (non-cancer) (100 abstracts)
Introduction: Previous reports have shown that subjects with insulin resistance have increased thyroid volume and nodule prevalence. We investigated the effects of metformin on thyroid volume and nodule size.
Methods: This prospective data were gathered on newly diagnosed subjects with insulin resistance (n=100, 68 female, 32 male) between August 2008 and May 2010. Measurements of thyroid hormones and thyroid ultrasonography was performed in all participants before and after 6 months therapy of metformin.
Results: Mean BMI and waist circumference decreased significantly after metformin therapy (34.5±5.1 vs 32.7±4.8 kg/m2 and 106.3±11.8 vs 101.8±19.0 cm respectively) (P<0.0001 for BMI; P=0.008 for waist circumference). Insulin resistance estimated by homeostasis model assessment also decreased after metformin therapy (4.5±1.9 vs 2.9±1.7, P <0.0001). After metformin therapy, mean TSH level was lower (1.8±1.0 vs 1.5±0.8 mIU/l, P<0.0001), mean free T3 was higher (2.7±0.7 vs 3.0±0.8 pg/ml, P=0.03), and mean free T4 was similar (1.4±0.6 vs 1.5±1.3 ng/dl, P>0.5). Mean thyroid volume (22.5±11.2 vs 20.3±10.4 ml, P<0.0001) and mean thyroid nodule size (12.9±7.6 vs 11.7±7.2 mm, P<0.0001) also decreased after treatment.
Conclusions: In subjects with insulin resistance, metformin therapy significantly decreases thyroid volume and nodule size, which seems to not only shed light on novel aspects in pathophysiology of goiter, but also to introduce therapeutic challenges as well.