From the Guidelines
Taking levothyroxine without having hypothyroidism is not recommended and potentially harmful. Levothyroxine is a prescription medication specifically designed to replace or supplement thyroid hormone in people with hypothyroidism or other thyroid disorders. When someone with normal thyroid function takes levothyroxine, it can cause hyperthyroidism (excess thyroid hormone), leading to symptoms such as rapid heart rate, anxiety, tremors, weight loss, heat intolerance, and sleep problems. In severe cases, it can cause heart arrhythmias or even thyroid storm, a life-threatening condition. Some people mistakenly believe levothyroxine can help with weight loss or energy levels in those with normal thyroid function, but this is incorrect and dangerous. Thyroid hormone levels are carefully regulated by the body, and disrupting this balance without medical need can have serious consequences.
According to the US Preventive Services Task Force recommendation statement 1, there is limited evidence available to assess the harms of treatment of thyroid dysfunction. The previous review found that one quarter of patients who received levothyroxine were inadvertently maintained on doses high enough to make TSH levels undetectable, which could increase the risk for osteoporosis, fractures, abnormal cardiac output, or ventricular hypertrophy 1.
The potential harms of taking levothyroxine without hypothyroidism include:
- Hyperthyroidism (excess thyroid hormone)
- Rapid heart rate
- Anxiety
- Tremors
- Weight loss
- Heat intolerance
- Sleep problems
- Heart arrhythmias
- Thyroid storm (a life-threatening condition)
Only take levothyroxine if prescribed by a healthcare provider who has diagnosed you with hypothyroidism or another condition requiring thyroid hormone replacement, and follow their dosing instructions precisely. The USPSTF did not identify any studies that evaluated the benefits of treatment of subclinical hyperthyroidism on final health outcomes, such as fractures, cancer, or cardiovascular morbidity or mortality 1.
In the case of asymptomatic hyperthyroidism, overtreatment may be of even greater concern given that one treatment option is ablation of the thyroid gland followed by thyroid replacement therapy 1. Patients who are overdiagnosed and overtreated could develop iatrogenic hypothyroidism and become dependent on lifelong thyroid hormone therapy.
Therefore, it is essential to only take levothyroxine under the guidance of a healthcare provider and with a confirmed diagnosis of hypothyroidism or another condition requiring thyroid hormone replacement.
From the Research
Taking Levothyroxine Without Hypothyroidism
- There is no clear evidence to support the use of levothyroxine in individuals without hypothyroidism, as it may lead to thyrotoxicosis and other adverse effects 2, 3, 4, 5.
- The decision to treat subclinical hypothyroidism with levothyroxine should be individualized based on patient age, degree of serum thyroid-stimulating hormone (TSH) elevation, symptoms, cardiovascular disease (CVD) risk, and other co-morbidities 3, 4, 5.
- Treatment with levothyroxine may only provide benefit in certain subgroups, such as patients who are younger or at higher risk of cardiovascular disease 3.
- In patients with subclinical hypothyroidism, treatment is not necessary unless the TSH exceeds 7.0-10 mIU/L, and even then, treatment does not improve symptoms or cognitive function if the TSH is less than 10 mIU/L 4, 5.
- Cardiovascular events may be reduced in patients under age 65 with subclinical hypothyroidism who are treated with levothyroxine, but treatment may be harmful in elderly patients with subclinical hypothyroidism 4, 5.
Risks and Considerations
- Overzealous treatment of symptomatic patients with subclinical hypothyroidism may contribute to dissatisfaction among hypothyroidism patients, as potential hypothyroid symptoms in patients with minimal hypothyroidism rarely respond to treatment 4.
- Levothyroxine therapy may be associated with iatrogenic thyrotoxicosis, especially in elderly patients, and there is no evidence that it is beneficial in persons aged 65 years or older 5.
- The diagnosis of subclinical hypothyroidism should be confirmed by repeat thyroid function tests ideally obtained at least 2 months later, as 62% of elevated TSH levels may revert to normal spontaneously 4.
Alternatives and Special Considerations
- In some hypothyroid patients who are dissatisfied with treatment, especially those with a polymorphism in type 2 deiodinase, combined treatment with levothyroxine and liothyronine may be preferred 4.
- TSH goals are age dependent, with a 97.5 percentile (upper limit of normal) of 3.6 mIU/L for patients under age 40, and 7.5 mIU/L for patients over age 80 4.