Correlation between serum leptin levels and insulin sensitivity in diffuse toxic goiter

[Early improvement in Type 2 diabetes in obese patients following gastric bypass and bilio-pancreatic diversion: the role of the entero-insular axis]

Improvement in Type 2 diabetes is seen in 80-98% of obese diabetic patients who undergo gastric bypass or bilio-pancreatic diversion. This improvement is evident early after the operation before significant weight loss has occurred. Although numerous teams have extensively studied the physiology of this early post-bypass amelioration of type 2 diabetes, the exact mechanism of diabetes remission remains unclear. Studies have focused on changes in the entero-insular axis, which is mediated in part by the interaction of insulinotropic hormones GIP and GIP 1 on the beta islet cells of the pancreas. Other mechanisms which have been postulated focus on the adipo-insular axis; the actions of adiponectin and leptin seem to have an important role in insulin resistance but their action is weight-loss dependent. Post-operative caloric restriction may also contribute to the early resolution of type 2 diabetes observed after gastric bypass and bilio- pancreatic diversion.

Absence of thyrotropin-induced increase in leptin levels in patients with history of differentiated thyroid carcinoma undergoing recombinant human thyrotropin testing

BACKGROUND

Some extra-thyroid effects of TSH have been described in vitro and in vivo. TSH has recently been suggested to induce interleukin-6 secretion by adipocytes. Leptin is the main protein secreted by adipose tissue.

OBJECTIVE

The aim of our study was to evaluate the acute effect of the recombinant human TSH (rhTSH)-induced TSH surge on serum leptin levels in thyroidectomized patients undergoing levothyroxine (L-T4) suppressive therapy for differentiated thyroid carcinoma (DTC).

DESIGN

A cohort of 15 female DTC patients was evaluated. Standard rhTSH testing was performed. Leptin, TSH, thyroid hormones, and thyroglobulin were measured before and 3, 6, and 9 days after rhTSH testing. Some metabolic parameters were also evaluated at the baseline.

RESULTS

Baseline leptin levels were 12.2+/-3.2 microg/l. Only body mass index (BMI) correlated significantly (p<0.05) with leptin levels. After rhTSH administration, TSH levels increased significantly (p<0.001), while thyroid hormones remained unchanged. Twenty hours after the last rhTSH administration, leptin (11.8+/-3.0 microg/l) levels were unchanged. The maximal TSH level was negatively related with BMI (p<0.05), but no correlation between maximal TSH and leptin levels after rhTSH was noted.

CONCLUSIONS

Our in vivo experimental model suggests that an acute TSH increase after rhTSH testing is ineffective in changing circulating leptin levels.

Thyroid and leptin

Leptin, which is produced by adipocytes, is known to be an important regulator of food intake and energy storage. Disturbance of thyroid function is associated with marked changes in both body weight and energy expenditure, and it has therefore been the subject of much research to study the mutual roles of leptin and thyroid hormones in this respect. Despite intensive research in this field, results are still not very clear. The aim of this review has been to update the current state of knowledge of leptin related to thyroid pathophysiology.