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Subclinical hypothyroidism and mortality in a large Austrian cohort: a possible impact on treatment?
Florian Maria Kovar1, I-Fei Fang2, Thomas Perkmann3
1Department for Trauma Surgery, Medical University of Vienna, Vienna, Austria.
Insights
Subclinical hypothyroidism (SCH) may increase mortality risk, particularly in men under 60. Further studies are needed to determine if thyroid hormone replacement therapy is beneficial for this group.
Area of Science:
- Endocrinology
- Cardiovascular Medicine
- Epidemiology
Background:
- The clinical significance of subclinical hypothyroidism (SCH) remains debated, impacting treatment decisions.
- Existing research lacks consensus on whether to treat SCH, necessitating further investigation into its long-term health consequences.
Purpose of the Study:
- To investigate the association between subclinical hypothyroidism and overall and vascular mortality.
- To determine if SCH poses an independent risk factor for mortality.
Main Methods:
- A retrospective cohort study involving 103,135 individuals with baseline thyroid-stimulating hormone (TSH) and free thyroxine (fT4) measurements.
- Subclinical hypothyroidism defined as TSH 4.5–20.0 mIU/L with normal fT4 (0.7–1.7 ng/dL).
- Mortality data assessed via linkage with the Austrian Death Registry.
Main Results:
- Of 80,490 eligible subjects, 3,934 (3.7%) had SCH.
- A dose-dependent association was observed between TSH levels and all-cause mortality in a multivariate Cox regression model.
- The risk of overall and vascular mortality associated with SCH was notably higher in men under 60 compared to women or older men.
Conclusions:
- Subclinical hypothyroidism appears to be an independent risk factor for overall and vascular mortality, especially in younger men.
- The findings suggest a potential benefit of thyroid hormone replacement therapy in specific SCH populations, warranting further evaluation in clinical trials.
Background:
Clinical implications of subclinical hypothyroidism (SCH) are still matter of intense debate, resulting in the controversial discussion whether subclinical hypothyroidism should be treated. We performed a cohort study to evaluate the impact of subclinical hypothyroidism on vascular and overall mortality.
Methods:
Between 02/1993 and 03/2004, a total of 103,135 persons attending the General Hospital Vienna with baseline serum thyrotropin (TSH, thyroid-stimulating hormone) and free thyroxin (fT4) measurements could be enrolled in a retrospective cohort study. Subclinical hypothyroidism was defined by elevated TSH ranging from 4.5 to 20.0 mIU/L and normal fT4 concentration (0.7-1.7 ng/dL). Overall and vascular mortality as primary endpoints were assessed via record linkage with the Austrian Death Registry.
Results:
A total of 80,490 subjects fulfilled inclusion criteria of whom 3934 participants (3.7%) were classified as SCH (868 males and 3066 females, median age 48 years). The mean follow-up among the 80,490 subjects was 4.1 years yielding an observation period of 373,301 person-years at risk. In a multivariate Cox regression model adjusted for age and gender TSH levels showed a dose-dependent association with all-cause mortality. The association between SCH and overall or vascular mortality was stronger in men below 60 years compared to older males or females.
Conclusion:
Our data support the hypothesis that SCH might represent an independent risk factor for overall and vascular mortality, especially in men below 60 years. Whether this group would benefit from replacement therapy should be evaluated in interventional studies.
