番茄社区

SAN JUAN -- Suppressing thyroid-stimulating hormone (TSH) after thyroidectomy for low-risk cancer increases the risk of osteoporosis in women without cutting back on cancer recurrence, researchers reported here.

In a retrospective study, women who had suppressed TSH levels had more than a three-fold increased risk of osteoporosis than those whose levels were not suppressed, , of Memorial Sloan Kettering Cancer Center (MSKCC) in New York City, and colleagues reported at the American Thyroid Association meeting.

"Therapeutic efforts should focus on avoiding harm in indolent disease," Wang said during her presentation.

After thyroidectomy for well-differentiated thyroid cancer, TSH is often suppressed because it stimulates thyroid cell proliferation, and a goal of treatment is to inhibit the growth of residual neoplastic tissue.

But there's no evidence-based consensus on the optimal TSH level that can help reduce recurrence while minimizing the risk of adverse effects, Wang said.

To assess the effects of TSH suppression on those effects -- in this study, a composite of atrial fibrillation and osteoporosis -- Wang and colleagues conducted a retrospective study of 771 patients who were treated for thyroid cancer at MSKCC from 2000 to 2006, and were followed for a median of 6.5 years.

They excluded patients with high-risk cancer, those with primary hyperparathyroidism, and those who had atrial fibrillation or osteoporosis before thyroidectomy.

After these exclusions, they were left with 756 patients in the atrial fibrillation analysis. For the osteoporosis analysis, they excluded men, and analyzed a total of 537 women.

TSH suppression was defined as a median level of 0.4 mU/L or less.

Overall, they saw no differences between those with suppressed TSH and those without in terms of disease-free survival, and multivariate analyses confirmed that TSH suppression was not a predictor of recurrence.

But for their composite outcome of adverse events, they did find a significantly increased risk with suppressed TSH levels.

Wang said the TSH suppressed group developed more events of harm at twice the rate of those who were not suppressed (hazard ratio 2.1, 95% CI 1.00 to 4.3, P=0.05).

However, when the analysis was broken down into either outcome, there was no significantly increased risk of atrial fibrillation with TSH suppression, Wang reported.

Yet there was a major divergence in osteoporosis risk, with a significantly higher risk for those with suppressed TSH (HR 3.5, 95% CI 1.2-10.2, P=0.023).

And in a multivariate analysis that controlled for age, a major confounder of osteoporosis risk, TSH remained a very strong predictor of osteoporosis, Wang said (HR 4.32, 95% CI 1.45-12.85, P=0.009).

In order to determine an optimal TSH level, the researchers looked at risk of osteoporosis and recurrence by TSH level and found that osteoporosis risk tapered with less suppression -- particularly for levels of 0.9 to 1 mU/L -- and risk of recurrence remained about the same at these levels.

Wang concluded that there's no recurrence benefit with TSH suppression, but an increased risk of harm, particularly for osteoporosis in women, and care should be taken with regard to TSH suppression in these patients who've had thyroidectomy for low-risk disease.

, of the University of Michigan in Ann Arbor, who was not involved in the study, said the findings "raise the question of whether TSH suppression is in fact necessary."

"More data are needed from a larger series of patients to inform practice guidelines, but these findings are potentially impactful since they highlight an area where revision might be indicated," Koenig told 番茄社区.

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