TSH Influences Serum Leptin Levels Independent of Thyroid Hormones in Hypothyroid and Hyperthyroid Patients

Abstract

Abstract. Leptin is considered to play a role in maintenance of energy balance and body weight by neuroendocrine mechanisms. The physiological mechanisms for thyroid hormone-induced alteration in serum leptin are not well known. In the present study, the relationship between thyroid hormones and leptin levels was investigated in patients with overt hypothyroidism and hyperthyroidism before and after successful treatment. Leptin levels were determined by radioimmunoassay and body mass index (BMI) was calculated for each subject. Serum leptin levels of 26 hypothyroid and 22 hyperthyroid patients were compared with those of 20 healthy volunteers who comprised the controls. Serum leptin levels of hypothyroid patients (28.4 ± 4.1 ng/ml) were found to be significantly higher than the controls (19.1 ± 3.2 ng/ml) (p<0.01), whereas hyperthyroid patients had lower levels (10.7 ± 1.2 ng/ml) (p<0.01). In hypothyroid patients, serum leptin levels were decreased significantly to 20.6 ± 2.1 ng/ml with thyroxin treatment (p<0.05). However, in hyperthyroid group, serum leptin levels were increased to 12.4 ± 2.2 ng/ml by treatment (p>0.05). BMI was not changed with the treatment in either group. The serum leptin levels were correlated with BMI and thyrotropin (TSH) in both hypothyroid and hyperthyroid patients. Serum leptin levels are affected in thyroid disorders and the correlation of leptin with TSH is independent of thyroid hormones.

The Interconnections Between Obesity, Thyroid Function, and Autoimmunity: The Multifold Role of Leptin

“…Moreover, T4 treatment decreased serum leptin levels in hypothyroid patients, whereas in hyperthyroidism, thyrostatic treatment increased leptin levels. In both hypothyroid and hyperthyroid patients, leptin levels were found to be correlated with BMI and TSH (31). Furthermore, in another study, fasting plasma leptin concentrations in obese OH patients were threefold higher than in lean OH, and twofold higher than in obese hyperthyroid patients (32).…”

Changes in the before and after thyroxine treatment levels of adipose tissue, leptin, and resistin in subclinical hypothyroid patients

“…There are also studies reporting L-thyroxin treatment to have caused increased [11,44], not changed [45,46], or lowered [17,19,23] leptin levels. We observed a significant decrease in leptin levels after euthyroidism was achieved.…”

“…One study has shown that even small increases in serum TSH concentrations within normal reference ranges may be associated with increased weight [8], as thyroid hormones, leptin, and resistin are involved in energy metabolism and weight changes. While a majority of studies report normal leptin levels among hypothyroid patients [9][10][11][12], there are studies reporting low [13][14][15][16] or high [17][18][19] levels of leptin as well. Similarly, low [10,13], normal [20], and high [18] resistin levels have been reported in hypothyroid cases.…”

Obesity and thyroid cancer

“…Potential stimulators of TSH production, explaining the increase in TSH in obese patients, include hormonal mediators of adipose tissue, especially leptin (Rosenbaum et al 2000, Sari et al 2003. Apart from modulating food intake and energy expenditure, leptin acts as a neuroendocrine regulator of the hypothalamic-pituitary-thyroid axis by regulating the expression of TRH in the paraventricular nucleus; leptin secretion by adipose tissue will then be stimulated by TSH (Menendez et al 2003, Oge et al 2005, Feldt-Rasmussen 2007, Santini et al 2010. Leptin may also affect deiodinases, activating the T 4 to T 3 conversion (Zimmermann-Belsing et al 2003, Reinehr 2010.…”