Relationship between Thyroid Volume and Iodine, Leptin, and Adiponectin in Obese Women before and after Weight Loss

Objective: To investigate whether or not reduction of thyroid volume during weight loss is related to adipocytokines and urinary iodine excretion in obese women. Subjects and Methods: 98 obese and 31 non-obese women consecutively admitted to the endocrinology and metabolism outpatient clinic of the School of Medicine, Akdeniz University were included in the study. Thyroid volume, thyroid function tests, leptin and adiponectin levels, and urinary iodine excretion were measured at baseline and six months after treatment for obesity. Results: Thyroid volume increased in obese women (p = 0.048). After adjustment for body mass index, there were no significant differences in plasma leptin and serum adiponectin levels between obese and non-obese women (p > 0.05). Thyroid volume correlated positively with body mass index (r = 0.48, p = 0.04), leptin (r = 0.1, p = 0.03), and thyroid-stimulating hormone (r = 0.43, p = 0.001) levels, while there was a negative correlation between thyroid volume and urinary iodine (r = –0.38, p = 0.04) and urinary iodine/creatinine ratio (r = –0.25, p = 0.045) in obese women. Changes in body mass index (p = 0.022) and leptin levels (p = 0.039) were the only factors that significantly affected the change of thyroid volume during weight loss. Conclusion: Iodine status may play an important role in increased thyroid volume in obese women; however, iodine status did not seem to exert a significant influence on the changes in thyroid volume. On the other hand, changes in both body mass index and plasma leptin levels seemed to be important for changes in thyroid volume.