High Cardiovascular Risks Linked to Persistent Subclinical Hypothyroidism

Diseased thyroid gland, conceptual computer illustration.
Persistent subclinical hypothyroidism is linked to severe cardiovascular disease; monitoring thyroid levels may aid in identifying patients at risk.

Persistent subclinical hypothyroidism (SCH) is associated with increased severity of coronary artery lesions and major adverse cardiovascular and cerebral events (MACCE) and may be a prognostic factor in patients with non–ST‐segment elevation acute coronary syndrome (NSTE‐ACS) following percutaneous coronary intervention (PCI), according to a study in Clinical Endocrinology.

Investigators evaluated changes in thyroid-stimulating hormone (TSH) levels to determine the differences in the severity of coronary artery lesions and clinical outcomes between NSTE‐ACS patients with normal thyroid function and those with persistent SCH after PCI and assessed the predictive value of TSH levels for major cardiovascular and cerebral events.

Gensini scores were used to analyze the severity of coronary artery lesions, which were divided into 3 grades: Gensini group 1 (score 0-26), Gensini group 2 (score 26.5-52), and Gensini group 3 (score >52).

A total of 1642 patients with NSTE‐ACS who had undergone PCI were selected for baseline TSH levels and periodic follow-up. Thyroid function tests were given to patients before PCI and at 1 day, 1 week, 1 month, and 6 months after PCI was performed, and patients were observed for a median of 28.3 months. Based on serum TSH levels, participants were categorized into the euthyroidism (ET) group (n = 1472; mean age 62.4±9.7 years; 33.3% female) or SCH group (n = 170; mean age 62.9±9.1 years; 48.2% female). The SCH detection rate for all 1642 patients was 10.4%.

TSH was significantly associated with the degree of coronary artery lesions, and it was an independent risk factor for Gensini group 2 (odds ratio [OR], 1.144; 95% CI, 1.057-1.237; P = .001) and Gensini group 3 (OR, 1.131; 95% CI, 1.043-1.226; P = .003).

The risk of MACCE (hazard ratio [HR], 4.067; P < .001), nonfatal myocardial infarction (HR, 14.724; P = .003), and unplanned PCI (HR, 5.028; P < .001) was higher in the SCH group than in the ET group, after adjustment for covariates.

Differences between the 2 groups were not significant regarding the incidence of heart failure (HR, 6.012; P = .175), nonfatal stroke (HR, 2.039; P = .302), unplanned coronary artery bypass grafting (HR, 1.541; P = .57), or cardiac death (HR, 2.704; P = .375).

Patients enrolled in the study did not undergo antithyroid autoantibody or thyroid ultrasound examinations, which may have missed those with thyroiditis, and researchers said this was one of the limitations of the study. High levels of phosphorus and calcium are considered risk factors for patients with chronic kidney disease, but these were not measured in the study either. Additionally, researchers acknowledged the power of their study was calculated by estimating the occurrence of MACCE, so comparisons of the occurrence of each component outcome may have been underpowered.

It is still unclear whether persistent SCH is associated with the severity of coronary disease and cerebral events in patients with NSTE-ACS following PCI, according to the authors, but they offered a preliminary conclusion based on their study results.

“We observed that persistent SCH, which was defined by repeatedly monitoring serum TSH levels, was associated with more severe coronary artery lesions and had a higher risk of nonfatal myocardial infarction and unplanned PCI,” they said. . “Persistent SCH, which is independent of other recognized traditional risk factors, is an important predictor of MACCE in patients with NSTE‐ACS treated with PCI.”


Han C, Xu K, Wang L, et al. Impact of persistent subclinical hypothyroidism on clinical outcomes in non‐ST‐segment elevation acute coronary syndrome undergoing percutaneous coronary intervention. Clin Endocrinol. Published online October 12, 2021. doi:10.1111/cen.14613