medwireNews: Subclinical hypothyroidism is not an independent predictor for clinical outcomes in patients with papillary thyroid carcinoma (PTC), research shows.
In addition, preoperative subclinical hypothyroidism was not an independent predictor for tumor aggressiveness.
As reported in the American Journal of Otolaryngology, lead researcher Dongbin Ahn (Kyungpook National University, Daegu, Korea) and colleagues found there was no significant difference in tumor size, extra-thyroidal extension (ETE), and multifocality between euthyroid patients and those with subclinical hypothyroidism.
The incidence of lymph node metastasis was lower in patients with subclinical hypothyroidism compared with euthyroid patients, but the difference was not statistically significant.
"This result contradicts previously reported studies on the role of TSH [thyroid-stimulating hormone] in thyroid cancer," state the researchers. Several preclinical studies had shown that thyroid hormone deprivation could slow tumor growth and thyroid hormone supplementation could increase tumor growth.
In the present study, the mean concentration of TSH was 1.86 mIU/L in 257 preoperative euthyroid patients and 6.86 mIU/L in 35 patients with subclinical hypothyroidism, a statistically significant difference.
However, there were no significant differences in tumor size, ETE, and multifocality between the subclinical hypothyroidism and euthyroid patients. The rate of lymph node metastasis was actually lower among patients with subclinical hypothyroidism than euthyroid patients, at 8.6% versus 21.8%, but not significantly so.
During a mean follow up of 82 months, patients with subclinical hypothyroidism tended to have a better prognosis in terms of recurrence and 7-year survival rates, but again this difference was not significant.
The researchers observed no correlation between TSH concentrations and various prognostic parameters, even as TSH concentrations increased.
"Generally, age, ETE, and multifocality show a rising trend with respect to an increase in TSH concentrations, whereas primary tumor size, lymph node metastasis, and recurrence show a decreasing trend," write Ahn and colleagues.
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