BackgroundThere is a proven relationship between obesity and several cancers including breast, endometrium, colorectal, and esophagus. With the increasing incidence of both obesity and thyroid cancer, we designed the present study to investigate a causal relationship between leptin, which is one of the well known adipokines, and well-differentiated thyroid cancer (WDTC).MethodsSerum leptin levels were measured in 30 patients with WDTC and compared to 30 healthy control subjects before and 1 month after surgery. Other parameters studied included age, sex, body mass index, menopausal status in women, lymph node status, tumor size, and disease multifocality.ResultsThere were no differences between the two groups regarding age and sex. Preoperative leptin levels were higher in the WDTC patients when compared to the control patients [19.25 (1.50–109.60) vs 0.90 (0.50–11.80) ng/ml, p < 0.001, group 1 vs group 2, respectively]. A significant drop in leptin levels 1 month after surgery occurred in the WDTC group, falling from 19.25 (1.50–109.60) to 0.90 (0.60–8.90) ng/ml (p < 0.001). This did not occur in the control group (p = 0.274). Lymph node involvement, tumor size, and multifocality had no effect on leptin levels, although trends were observed (p = 0.48, 0.079, and 0.064), respectively.ConclusionsSerum leptin levels were significantly higher in WDTC patients when compared to control group patients, with a significant drop after surgery. Leptin may play a role in diagnosis of WDTC; however, its prognostic value is still undetermined.

Dear Editor,We would like to thank Dr Sertoglu et al. for their interest and constructive comments towards our recently published article investigating the relation between welldifferentiated thyroid cancer and serum leptin levels [1], [2].Concerning the question as to whether obesity has influenced leptin levels through inflammatory processes, we acknowledge the role of a chronic inflammatory process that is associated with obesity through mediation of cytokines [3], [4]. We have measured both erythrocyte sedimentation rate and C-reactive protein which are a part of the routine work up for all our patients. There was no significant difference between the levels in cases and control, and therefore, this was not mentioned in the original study. There are several factors which affect serum leptin levels, and to overcome this problem, control serum leptin levels were measured to remove the effect of bias and reveal the true association between serum leptin levels and well-differentiated thyroid cancer [1].Dr Sertoglo has also raised another important question regarding the dietary intake of the patients and their influence on the serum leptin levels with special emphasis on omega-3 fatty acid. The intake of omega-3 is not a regular supplement in our country, and therefore its effect has not been studied. Fish, however, which contains omega-3, is a major constituent of the diet of many people in Alexandria as it is a Mediterranean city. The effects of this may influence leptin levels but would be very hard to study. It is worth mentioning that we reviewed the dietary intake of all patients in the study and found no difference in dietary constituents.We continue to study the relation between serum leptin levels and thyroid cancer and will take Dr Sertoglo's comments into account in our future studies.

Background There is a proven relationship between obesity and several cancers including breast, endometrium, colorectal, and esophagus. With the increasing incidence of both obesity and thyroid cancer, we designed the present study to investigate a causal relationship between leptin, which is one of the well known adipokines, and well-differentiated thyroid cancer (WDTC). Methods Serum leptin levels were measured in 30 patients with WDTC and compared to 30 healthy control subjects before and 1 month after surgery. Other parameters studied included age, sex, body mass index, menopausal status in women, lymph node status, tumor size, and disease multifocality. Results There were no differences between the two groups regarding age and sex. Preoperative leptin levels were higher in the WDTC patients when compared to the control patients [19.25 (1.50-109.60) vs 0.90 (0.50-11.80) ng/ml, p \ 0.001, group 1 vs group 2, respectively]. A significant drop in leptin levels 1 month after surgery occurred in the WDTC group, falling from 19.25 (1.50-109.60) to 0.90 (0.60-8.90) ng/ml (p \ 0.001). This did not occur in the control group (p = 0.274). Lymph node involvement, tumor size, and multifocality had no effect on leptin levels, although trends were observed (p = 0.48, 0.079, and 0.064), respectively. Conclusions Serum leptin levels were significantly higher in WDTC patients when compared to control group patients, with a significant drop after surgery. Leptin may play a role in diagnosis of WDTC; however, its prognostic value is still undetermined.

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