Can your weight give you thyroid cancer?
When we talk about obesity, we immediately think of metabolic syndrome, diabetes, dyslipidemia, arterial hypertension, and reduced mobility. However, an elevated BMI may also be associated with other conditions. Did you know that one of them may be thyroid cancer?
Wait! You are not going to develop thyroid cancer simply because you have an elevated BMI. Let me explain...
Thyroid carcinoma can occur in patients with Graves’ disease. The reported incidence of this association ranges from 1% to 22%, and appears to be increasing. Younger age, the presence of thyroid nodules, and elevated TRAb levels have been reported as potential risk factors for thyroid carcinoma in patients with Graves’ disease. However, the contribution of an elevated BMI to this association has not been consistent across studies.
A recent publication by Dr. Ozan Caliskan and colleagues from Istanbul, Türkiye, in The Laryngoscope, retrospectively analyzed 206 patients who underwent thyroidectomy for Graves’ disease. The aim was to identify risk factors for thyroid malignancy and, in particular, to investigate the role of BMI.
The authors excluded patients who had previously been treated with radioactive iodine, as well as those presenting with distant metastases from papillary thyroid carcinoma at diagnosis. All patients were receiving antithyroid drugs and were euthyroid at the time of surgery. Indications for surgery included large symptomatic goiters, moderate-to-severe ophthalmopathy, patient preference, and intolerance to antithyroid medication, among others.
Total thyroidectomy was performed in 204 patients. One patient underwent total thyroidectomy with central and lateral neck dissection, while another underwent lobectomy followed by completion thyroidectomy because of a loss of signal (LOS) during the initial operation, without clinical consequences.
Among the 206 patients, 42 (20.4%) were diagnosed with papillary thyroid carcinoma. In 31% of these cancer cases, the diagnosis was an incidental finding, corresponding to 6.3% of the entire study population. Preoperatively detected thyroid nodules were present in 42.8% of patients with a cancer diagnosis, and 26.2% of these cancers had been diagnosed before surgery.
The results regarding the potential risk factors were particularly interesting.
Female sex was significantly more common (p = 0.026) among patients with Graves’ disease and thyroid cancer. In fact, women had a 2.9-fold higher risk of malignancy.
The presence of thyroid nodules was also significantly more frequent in the subgroup with thyroid carcinoma (p < 0.001), and was associated with a 3.3-fold higher risk of cancer.
Finally, BMI was significantly higher (p = 0.001) among patients with Graves’ disease and papillary thyroid carcinoma. According to Dr. Ozan Caliskan and colleagues, “each 1 kg/m² increase in BMI was associated with a 13% increased risk of malignancy.” They also identified a BMI cutoff value of 26.4 kg/m².
So, what do these results mean?
According to this study, a patient with Graves’ disease appears to have a higher likelihood of being diagnosed with papillary thyroid carcinoma if they are female, have thyroid nodules, and have a BMI above 26.4 kg/m².
Does this mean that surgery should potentially be the first option in these patients? Well...
As the authors point out, these results reflect only the population of patients who underwent surgery, raising the possibility that the true prevalence of thyroid carcinoma among all patients with Graves’ disease may be higher. In this context, it is easy to argue that “thyroidectomy not only provides definitive treatment for Graves’ disease but also enables the treatment and histopathological detection of occult malignancies.”
But another question arises: would these occult cancers ever cause problems in the future? Would they grow or spread?
We know that most papillary thyroid carcinomas are very indolent in their development, and some may never become clinically significant. Nevertheless, the word “cancer” carries a particular weight. Even when the disease is considered highly indolent or unlikely to cause harm, that possibility still exists. That is why knowing that a cancer is present, or may be present, is not something most patients would find easy to live with. In the end, we should weigh the potential risks associated with the cancer against those associated with surgery and make the treatment decision together with the patient. But that is another topic...
Returning to the association between overweight and thyroid malignancy, in addition to several studies supporting the authors’ findings in Graves’ disease, Dr. Ozan Caliskan et al. point out that thyroid cancer may exhibit more aggressive behavior in overweight patients, regardless of whether they have Graves’ disease.
An interesting point raised by the authors is the potential influence of the weight loss that patients may experience as a result of the metabolic changes associated with hyperthyroidism. This weight loss may underestimate the true association between BMI and thyroid malignancy. This means that a patient may have thyroid cancer in the setting of Graves’ disease but still have a normal BMI because of weight loss caused by hyperthyroidism, despite having previously been overweight. Consequently, this patient would not be classified as an overweight patient with thyroid cancer and Graves’ disease at the time of surgery.
Finally, I would like to highlight three ideas from the discussion section.
First, thyroid nodules are considered the strongest predictor of thyroid malignancy in patients with Graves’ disease, with some studies reporting up to a five-fold increase in the risk of thyroid cancer. This is why the authors reinforce the importance of ultrasound evaluation and cytology in patients with Graves’ disease when thyroid nodules are identified. This is huge.
Second, BMI is indeed associated with an increased risk of thyroid cancer in Graves’ disease, but “BMI alone may not be sufficient as a standalone predictor and should be interpreted together with other clinical and ultrasonographic characteristics.” Dr. Ozan and colleagues point out that, in the subgroup of patients without thyroid nodules, BMI was still associated with an increased risk of malignancy, although the association did not reach statistical significance. I think this is particularly important and is very much in line with what medicine—and carcinogenesis—are all about: multifactorial.
Third, knowing that female sex, the presence of thyroid nodules, and being overweight are risk factors for papillary thyroid carcinoma in the setting of Graves’ disease “may assist surgeons in preoperative risk stratification and surgical decision-making.
I leave you with this: always remember, no risk factor will ever walk alone.
Thank you to Dr. Ozan Çalışkan and Dr. Nurcihan Aygun for sending me their great work. It was a pleasure to read such an interesting paper, and to write this post. Congratulations for your work.
Link to article:
Dr. Carlos Eduardo Costa Almeida
General Surgeon
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