Thyroid cancer patients have low adiponectin levels
MedWire News: Patients with thyroid cancer have significantly lower levels of adiponectin than healthy individuals, suggest study results.
However, there is no evidence for a direct effect of adiponectin on thyroid cancer cells, say the researchers, who suggest that the observed negative association "may be attributed to the metabolic effects of adiponectin."
Circulating levels of adiponectin are lower in patients with endometrial, prostate, colorectal, renal, and postmenopausal breast cancer, than in people without cancer.
To assess whether adiponectin levels are also low in thyroid cancer patients, Christos Mantzoros (Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA) and colleagues measured levels of the adipokine in 175 thyroid cancer patients and 107 healthy individuals (controls).
They found that adiponectin levels were significantly lower in patients with thyroid cancer than controls, at 17.00 versus 19.26 µg/ml, respectively.
Participants in the top tertile (21.40 ng/ml or more) of adiponectin concentrations were 71% less likely than those in the bottom tertile (less than 17.99 ng/ml) to have thyroid cancer of any type, after adjusting for potential confounders including age, gender, and diabetes status.
"Adiponectin, particularly the high molecular weight forms, inhibits prostate cancer cell growth; suppresses leptin-, insulin growth factor-I-, and dihydrotestosterone-stimulated prostate carcinoma cell growth; and enhances the anticancer activity of doxorubicin in vitro," explain Mantzoros et al, as well as having "a significant dose-dependent growth inhibition of breast cancer cells in vitro."
To test the direct effects of adiponectin on thyroid cancer cells, Mantzoros and team exposed a thyroid cancer cell line to recombinant adiponectin in vitro. Despite the fact that the thyroid tumor tissues express adiponectin receptors, no significant direct effects of adiponectin on the cells were observed.
"Our results suggest that the observed inverse association between circulating adiponectin levels and risk of thyroid cancer in humans could be attributed to indirect effects of adiponectin, possibly through regulation of metabolism and insulin resistance," write the authors in the Journal of Clinical Endocrinology and Metabolism.
"Interestingly, the strength of the association between adiponectin levels and thyroid cancer was somewhat attenuated after adjusting for thyroid stimulating hormone, diabetes status, smoking status, body mass index (BMI), height, weight, age, free thyroxin 4, and gender, suggesting that metabolic parameters (possibly related to BMI) mediate at least a part of the association between adiponectin levels and risk of thyroid cancer," they note.
By Helen Albert