Levothyroxine Use in Older Adults with Subclinical Hypothyroidism and Cardiovascular Outcomes
Overview
In a UK cohort of adults over 50 with subclinical hypothyroidism, levothyroxine therapy was associated with a modest reduction in cardiovascular events but increased risks of bone complications and all-cause mortality. These findings highlight a complex risk-benefit profile for levothyroxine treatment in this population.
Background
Subclinical hypothyroidism (SCH), characterized by elevated TSH with normal free thyroxine, is common in older adults and often leads to levothyroxine (LT4) prescriptions. However, TSH levels naturally rise with age, and standard reference ranges may lead to overdiagnosis and overtreatment. While overt hypothyroidism warrants LT4 therapy, the benefits and harms of treating SCH in older adults remain uncertain, particularly regarding cardiovascular and bone health outcomes.
Data Highlights
Outcome
Hazard Ratio (HR)
95% Confidence Interval
P-value
Cardiovascular events
0.91
0.87-0.97
< .001
Bone events (fragility fractures or osteoporosis)
1.21
1.14-1.28
< .001
All-cause mortality
1.17
1.13-1.22
< .001
Key Findings
The study included 53,899 patients aged >50 years with subclinical hypothyroidism; 37% received levothyroxine.
Levothyroxine therapy was associated with a 9% reduction in cardiovascular events (HR 0.91; 95% CI 0.87-0.97; P < .001).
LT4 treatment increased the risk of bone-related events by 21% (HR 1.21; 95% CI 1.14-1.28; P < .001).
All-cause mortality was 17% higher in patients treated with LT4 (HR 1.17; 95% CI 1.13-1.22; P < .001).
TSH levels naturally rise with age, suggesting current reference intervals may lead to overdiagnosis of SCH in older adults.
Previous randomized trials showed no significant cardiovascular benefit from LT4 in older adults, but this large cohort suggests a modest protective effect.
Clinical Implications
Clinicians should carefully weigh the cardiovascular benefits of levothyroxine therapy against the increased risks of bone complications and mortality in older adults with subclinical hypothyroidism. Individualized treatment decisions and discussions about these trade-offs are essential, considering age-related changes in TSH and potential overtreatment harms.
Conclusion
Levothyroxine therapy in older adults with subclinical hypothyroidism offers modest cardiovascular protection but is linked to higher bone event rates and mortality. These findings underscore the need for cautious, personalized approaches to LT4 prescribing in this population.
References
ACEL-UK Study Group 2024 -- Evaluating the Impact of Levothyroxine on Cardiovascular Health in Older Adults in the United Kingdom: A Cohort Analysis
