Levothyroxine therapy may reduce CV risk for adults with subclinical hypothyroidism
Click Here to Manage Email Alerts
Key takeaways:
- Levothyroxine lowered the risk for myocardial infarction and CV-related death for adults with subclinical hypothyroidism.
- Researchers defined subclinical hypothyroidism as a TSH level between 5 mU/L and 10 mU/L.
Adults with subclinical hypothyroidism may have a lower risk for major adverse cardiovascular events if they receive levothyroxine therapy compared with no treatment, according to a study published in Thyroid.
In an analysis of data from the Clinical Practice Research Datalink in the U.K., adults with subclinical hypothyroidism, defined as two thyroid-stimulating hormone measurements between 5 mU/L and 10 mU/L within 1 year of each other, were 12% less likely to have a major adverse CV event (MACE) if they were treated with levothyroxine. However, Oriana Hoi Yun Yu, MD, MSc, associate professor in the division of endocrinology, Centre for Clinical Epidemiology, Lady Davis Institute at the Jewish General Hospital and the department of medicine at McGill University in Montreal, said the study cannot prove causality due to its observational nature.
“Further studies are needed to confirm these findings,” Yu told Healio. “Currently, most guidelines recommend treating subclinical hypothyroidism when TSH levels are above 10 mU/L.”
Yu and colleagues obtained electronic health record data from adults aged 18 years and older with new-onset subclinical hypothyroidism. Data were collected from April 1998 to 2018. Researchers used time-conditional propensity scoring to match 76,946 adults with subclinical hypothyroidism who were prescribed levothyroxine therapy to a group of 76,946 people with subclinical hypothyroidism who were untreated. The primary outcome was the occurrence of MACE, which was a composite endpoint of nonfatal myocardial infarction, nonfatal ischemic stroke and CV-related mortality. Heart failure hospitalization and all-cause mortality were assessed as secondary outcomes.
During a median follow-up of 1.6 years, MACE occurred among 2,028 adults receiving levothyroxine and 4,068 people in the untreated group. Adults using levothyroxine had a lower risk for MACE than untreated adults (incidence rates, 12.8 per 1,000 person-years vs. 13.9 per 1,000 person-years; adjusted HR = 0.88; 95% CI, 0.83-0.93).
“Prior research has shown that subclinical hypothyroidism is associated with increased risk of adverse CV events,” Yu said. “A prior observational study showed a decreased risk in CV outcomes associated with levothyroxine therapy in the treatment of subclinical hypothyroidism. In our study, the magnitude of the association between levothyroxine treatment and MACE was smaller.”
When the individual components of MACE were examined, levothyroxine was associated with a lower risk for nonfatal MI (aHR = 0.89; 95% CI, 0.81-0.97) and CV-related mortality (aHR = 0.83; 95% CI, 0.77-0.89) than no therapy. Adults using levothyroxine had a similar risk for nonfatal ischemic stroke and heart failure hospitalization as untreated adults. The risk for all-cause mortality was lower for the levothyroxine group compared with the untreated group (HR = 0.79; 95% CI, 0.76-0.82).
No differences in MACE risk were observed in analyses stratified by age, sex, history of renal insufficiency and history of cardiovascular disease.
Yu said more studies should be conducted to assess whether treating subclinical hypothyroidism with a TSH between 5 mU/L and 10 mU/L improves health outcomes.
For more information:
Oriana Hoi Yun Yu, MD, MSc, can be reached at hoi.yun.yu@mcgill.ca.
Collapse
Click Here to Manage Email Alerts