Hyperthyroidism leads to bone resorption, and interleukin-6 (IL-6) regulates osteoclast proliferation. Elevated serum IL-6 levels have been demonstrated previously in hyperthyridism. The purpose of the study was to see how the bone turnover rates and serum IL-6 levels are influenced by either overt or subclinical thyrotoxicosis in premenopausal women. The patients with toxic nodular goiters (TNG group, n: 20), with toxic diffuse goiters (TDG group, n: 20) and with subclinical thyrotoxicosis under levothyroxine treatment (L-T4 treatment group, n: 16) were evaluated and compared with euthyroid patients (control group, n: 20) in respect of their serum thyroid hormone levels, and bone turnover biochemical markers. Serum mean alkaline phosphatase (ALP) levels and ratio of Deoxypyridinoline/creatininie (DPD/cr) were significantly higher in TNG (ALP, 102.00±20.09 U/L: DPD/cr, 103.72±71.09 nM/mM, p<0.001), TDG (ALP, 120.10184.09 U/L: DPD/cr, 145.54±140.32 nM/mM, p<0.001), and L-T4 treatment (ALP, 85.31±36.16 U/L: DPD/cr, 54.71±27.07 nM/mM, p<0.001) groups than in the control group (ALP, 55.06±18.83 U/L: DPD/cr, 29-56±15.01 nM/mM). Serum mean osteocalcine (OC) levels were significantly higher in TNG (14.98±18.09 ng/ml, p<0.05), TDG (8.21±4.80 ng/ml, p<0.05) groups than in the control group (5.75±4.29 ng/ml), but not in the L-T4 tretment group (6.60±7.63 ng/ml, p>0.05). IL-6 levels were found significantly higher in TDG (46.17±50.41 pg/ml: p<0.05) and L-T4 treatment (11.24±12.24 pg/ml: p<0.05) groups than controls (IL-6, 2.73±1.48 pg/ml). in the TNG group, the serum IL-6 levels (7.83±16.06 pg/ml) showed a tendency lo increase, but this was not statistically significant (p>0.05).
This study showed that bone turnover increased in over and subclinical thyrotoxicosis. Because of the elevated serum IL-6 affeted by thyrotoxicosis of autoimmunity, it cannot be used as a sole marker of bone turnover
Keywords: IL-6, thyrotoxicosis, bone metabolism