Levothyroxine vs. Armour Thyroid
See how Levothyroxine and Armour Thyroid compare on approved uses, dosing, side effects, and cost.
Key Takeaways
Levothyroxine is a synthetic, FDA-approved T4-only hormone, while Armour Thyroid is a desiccated porcine extract containing both T4 and T3 that has never gone through FDA's standard drug approval process.
Levothyroxine's TSH-suppression use is limited to thyroid cancer, while Armour Thyroid is also used for TSH suppression in thyroid nodules, multinodular goiter, and Hashimoto's thyroiditis.
Armour Thyroid's animal-derived origin means hormone content can vary between batches and the drug is more prone to supply shortages than synthetic levothyroxine.
Levothyroxine vs. Armour Thyroid Drug Summary
Levothyroxine
Levothyroxine is a synthetic thyroid hormone (T4) used to treat hypothyroidism and to suppress TSH after thyroid cancer treatment. It comes as an oral tablet, capsule, or occasional IV injection taken once daily, with doses adjusted using periodic blood tests.
Armour Thyroid
Armour Thyroid is a desiccated porcine thyroid extract that supplies both T4 and T3 hormones, used to treat hypothyroidism and to suppress TSH in certain thyroid conditions. It comes as a once-daily oral tablet, with doses titrated slowly and adjusted using periodic blood tests.
Levothyroxine vs. Armour Thyroid Side Effects
Levothyroxine
Armour Thyroid
Levothyroxine vs. Armour Thyroid Dosage
Levothyroxine
Armour Thyroid
| STAGE | DOSE | WHEN |
| Starting dose | 12.5-25 mcg once daily | At the start |
| Maximum dose | 1.6 mcg/kg once daily | If needed |
| Dose changes | 2 increases | As tolerated |
| STAGE | DOSE | WHEN |
| Starting dose | 15 mg once daily | At the start |
| Maximum dose | 60-120 mg once daily | If needed |
| Dose changes | 3 increases | As tolerated |
Levothyroxine
| STAGE | DOSE | WHEN |
| Starting dose | 12.5-25 mcg once daily | At the start |
| Maximum dose | 1.6 mcg/kg once daily | If needed |
| Dose changes | 2 increases | As tolerated |
Armour Thyroid
| STAGE | DOSE | WHEN |
| Starting dose | 15 mg once daily | At the start |
| Maximum dose | 60-120 mg once daily | If needed |
| Dose changes | 3 increases | As tolerated |
Levothyroxine vs. Armour Thyroid Indications
Levothyroxine
Levothyroxine is FDA-approved to replace thyroid hormone in primary, secondary, or tertiary hypothyroidism and to suppress pituitary TSH in thyroid cancer management. It is not approved for weight loss, nontoxic goiter, or thyroiditis recovery, and carries a boxed warning against weight-loss use.
Primary, secondary, or tertiary hypothyroidism replacement
Pituitary TSH suppression in thyroid cancer
Not approved for weight loss or obesity (boxed warning)
Not approved for nontoxic goiter or thyroiditis recovery
Armour Thyroid
Armour Thyroid is approved to replace thyroid hormone in primary, secondary, or tertiary hypothyroidism and to suppress pituitary TSH in thyroid nodules, Hashimoto's thyroiditis, multinodular goiter, and thyroid cancer. It is not approved for weight loss or for infertility unrelated to hypothyroidism.
Primary, secondary, or tertiary hypothyroidism replacement
TSH suppression in thyroid nodules and multinodular goiter
TSH suppression in Hashimoto's thyroiditis and thyroid cancer
Not approved for weight loss or infertility treatment
Levothyroxine vs. Armour Thyroid Pros and Cons
Levothyroxine
Levothyroxine is FDA-approved through the standard NDA pathway, with synthetic hormone content that stays consistent from batch to batch. It is available as low-cost generic tablets and capsules and is covered by nearly all insurance plans.
Pros
FDA-approved through the standard new drug application process
Synthetic formulation gives precise, consistent hormone content
Generic price is much lower, roughly $4 to $50 a month versus $40 to $155 for Armour Thyroid
Cons
Contains only T4, so patients who feel better with added T3 may need a second medication
Absorption is sensitive to food, coffee, and timing of other medications
Switching between generic manufacturers can occasionally affect dosing consistency
Armour Thyroid
Armour Thyroid is a desiccated porcine thyroid extract that supplies both T4 and T3 hormones, unlike synthetic T4-only options. It has never gone through FDA's standard drug approval process and is marketed under a grandfathered status dating to before 1938.
Pros
Contains both T4 and T3, which some patients find improves symptom control
Approved for TSH suppression in a broader range of nodule and goiter conditions
Long history of clinical use predating modern approval requirements
Cons
Never went through FDA's standard approval process; sold as a grandfathered drug
Animal-derived extract means hormone content can vary between batches
More frequently affected by manufacturing shortages and recalls
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