From the Guidelines
The markedly elevated TSH of 107 indicates severe hypothyroidism, which is likely contributing to the patient's CHF exacerbation, and the next steps should include starting levothyroxine therapy with caution. The patient's age and heart failure require careful consideration when initiating treatment. According to the American Heart Association, thyroid function tests are recommended in all patients presenting with HF, as hypothyroidism and hyperthyroidism can coexist in patients with HF of various causes 1.
Key Considerations
- Begin with a low dose of levothyroxine, typically 25-50 mcg daily in a 91-year-old with cardiac disease, and gradually increase by 12.5-25 mcg every 4-6 weeks while monitoring TSH and cardiac status.
- Obtain free T4 levels to confirm the diagnosis before starting treatment.
- Severe hypothyroidism can worsen heart failure through several mechanisms: decreased cardiac contractility, reduced cardiac output, increased peripheral vascular resistance, and fluid retention due to impaired free water clearance, as noted in patients with hypothyroidism 1.
- Check for other precipitating factors of the CHF exacerbation and continue heart failure management.
- Monitor electrolytes, particularly as thyroid function normalizes.
- Consider endocrinology consultation for co-management of this complex case.
Monitoring and Precautions
- The patient should be monitored closely for signs of cardiac stress during thyroid hormone replacement, as rapid correction can potentially worsen cardiac symptoms in elderly patients with pre-existing heart disease 1.
- The low cardiac output in hypothyroidism is caused by bradycardia, a decrease in ventricular filling, and a decrease in cardiac contractility, which can be improved with thyroid hormonal replacement 1.
From the Research
Next Steps for the 91-Year-Old Patient
- The patient's markedly elevated TSH level of 107 suggests overt hypothyroidism, which is a common disorder due to inadequate thyroid hormone secretion 2.
- The next steps would be to confirm the diagnosis of hypothyroidism and assess the patient's symptoms and overall health status.
- According to the study by 2, levothyroxine therapy is recommended for patients with overt hypothyroidism and a blood TSH concentration above 10 mIU/L.
- However, the study by 3 suggests that TSH goals are age-dependent, and for patients over 80, the upper limit of normal is 7.5 mIU/L.
- The patient's age and overall health status should be taken into consideration when deciding on the treatment plan.
Contribution to Heart Failure
- Hypothyroidism can contribute to heart failure by causing a decrease in cardiac output, an increase in systemic vascular resistance, and a decrease in the body's ability to respond to stress 4.
- The study by 3 suggests that treatment of subclinical hypothyroidism may be harmful in elderly patients with subclinical hypothyroidism, and may even increase the risk of cardiovascular events.
- However, the study by 2 suggests that levothyroxine therapy can have a favorable harm-benefit balance in patients with overt hypothyroidism.
- Further evaluation is needed to determine the relationship between the patient's hypothyroidism and heart failure, and to develop an appropriate treatment plan.
Treatment Considerations
- Levothyroxine monotherapy is the standard of care for treatment of hypothyroidism, and the biochemical treatment goal is a TSH level within the reference range (0.4-4.0 mU/l) 5.
- However, the study by 6 suggests that combined treatment with levothyroxine and liothyronine may be preferred in some patients, especially those with a polymorphism in type 2 deiodinase.
- The patient's treatment plan should be individualized based on their specific needs and health status, and should be monitored closely to avoid over- or under-treatment.