Cardiovascular Disease in Patients With Thyroid Cancer and High Cholesterol

Patients with follicular thyroid cancer and an increased total cholesterol (TC) levels have a high incidence of atherosclerotic cardiovascular disease (ASCVD), researchers reported in the journal Medicine.

The retrospective study included patients with documented follicular thyroid cancer who were undergoing thyroidectomy. The investigators sought to compare the incidence of ASCVD according to serum TC level and assess the association of serum TC level with incident ASCVD.

A total of 348 patients with documented follicular thyroid cancer were included in the analysis. The patients were grouped according to their median serum TC level: low (TC 5.05±0.32 mmol/L) and high (TC 5.48±0.41mmol/L). The low TC group (n = 174) had a mean age of 52.9±10.8 years (35.6% male), and the high TC group (n = 174) had a mean age of 57.6±13.4 years (37.4% male).

Within 3 months of thyroidectomy, 31.6% of participants in the low TC group and 39.7% of the high TC group developed hypothyroidism (P < .05). The use of levothyroxine during follow-up was comparable in the 2 groups (29.3% vs 28.7% in the low and high TC groups, respectively).

The incidence rate of myocardial infarction was higher in the high TC group than in the low TC group, with an incidence rate ratio (IRR) of 2.11 (95% CI, 1.10-4.20). No between-group differences were observed in the incidence rate of ischemic stroke and cardiovascular death.

The incidence rate of composite ASCVD was higher in the high TC group compared with the low TC group, with an IRR of 1.69 (95% CI, 1.07-2.69).

After adjustment for hypothyroidism, the association of higher TC and composite ASCVD was attenuated into insignificance, with a hazard ratio (HR) of 0.92 (95% CI, 0.81-1.34). The HR increased to 0.97 (95% CI, 0.93-1.42) after additional adjustment for levothyroxine use.

Study limitations include the retrospective design and an acknowledgement that undetected and unmeasured covariates may have existed and therefore influenced the association of TC and ASCVD, although the researchers said they adjusted for potential covariates. It was also noted that all of the study participants were Chinese and it is unknown whether these findings can be extrapolated to other ethnic groups.

Researchers noted three main findings of their study: an incidence rate of composite ASCVD that was significantly higher in people with high serum TC levels postthyroidectomy; increased TC levels independently associated with an absolute 73% higher risk of composite ASCVD, and evidence that hypothyroidism seemed to play a crucial role in the link between increased serum TC levels and incident ASCVD.

“These findings together suggest that presence of hypothyroidism might portend an increased risk of ASCVD among patients with follicular thyroid cancer post-thyroidectomy, and levothyroxine therapy might help to mitigate the risk associated with hypothyroidism,” they concluded.

Reference

Huang G, Lu H, Li M, Lv Q, Chen Q. Association of total cholesterol and atherosclerotic cardiovascular disease in patients with follicular thyroid cancer: a real-world study from Chinese populations. Medicine (Baltimore). Published online October 1, 2021. doi:10.1097/MD.0000000000027310