From the Guidelines
Synthroid (levothyroxine) is generally recommended as the first-line treatment for hypothyroidism due to its consistent hormone content and extensive clinical evidence supporting its effectiveness. Armour Thyroid, a natural desiccated thyroid extract, contains both T3 and T4 hormones but has less consistent standardization and fewer large clinical trials supporting its use. Most endocrinology guidelines favor synthetic levothyroxine because it provides stable blood levels, has predictable absorption, and allows for precise dosing adjustments 1. Some patients report feeling better on Armour Thyroid, possibly due to its T3 content, which is the active form of thyroid hormone. However, the scientific evidence supporting superior outcomes with Armour is limited.
Key Considerations
- Treatment should be individualized based on patient response, with typical starting doses of 25-50 mcg for Synthroid, gradually adjusted based on TSH levels.
- Patients should take thyroid medication on an empty stomach, at least 30-60 minutes before eating, and avoid taking it with calcium, iron supplements, or certain medications that can interfere with absorption.
- Regular monitoring of thyroid function tests is essential regardless of which medication is chosen to ensure proper dosing and symptom control.
- The potential risks of overtreatment with levothyroxine, including osteoporosis, fractures, and cardiovascular issues, should be considered and monitored 1.
Evidence Summary
The evidence from the US Preventive Services Task Force recommendation statement and other studies suggests that levothyroxine is a safe and effective treatment for hypothyroidism, with a low risk of adverse effects when used appropriately 1. However, the evidence also highlights the importance of careful dosing and monitoring to avoid overtreatment and minimize potential harms.
From the Research
Synthroid vs Armour Thyroid Evidence
- The provided studies do not directly compare Synthroid and Armour Thyroid, but they discuss the treatment of hypothyroidism with levothyroxine (L-T4) and the potential benefits and drawbacks of combination therapy with liothyronine (L-T3) or animal thyroid extract 2, 3, 4, 5, 6.
- Levothyroxine (L-T4) monotherapy is the standard of care for hypothyroidism, but some patients may experience persistent symptoms despite normalization of serum thyrotropin levels 3, 4.
- Combination therapy with L-T4 and L-T3 may be considered for patients with persistent symptoms, but the current evidence is not sufficiently strong to support its use as the optimal approach 4.
- Some studies suggest that polymorphisms in deiodinase genes may contribute to unsatisfactory treatment results with L-T4 monotherapy, and that combination therapy with L-T4 and L-T3 may be preferred in these cases 3, 6.
- The diagnosis of subclinical hypothyroidism should be confirmed by repeat thyroid function tests, and treatment is not necessary unless the TSH exceeds 7.0-10 mIU/L 6.
- TSH goals are age-dependent, and treatment may be harmful in elderly patients with subclinical hypothyroidism 6.
- Personalized thyroid hormone replacement therapy is necessary to ensure optimal treatment outcomes for hypothyroid patients 5.