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

Most common
Headache (rate not quantified, dose-dependent)
Tremors (rate not quantified, dose-dependent)
Arrhythmias/palpitations (rate not quantified, dose-dependent)
Nervousness/irritability/insomnia (rate not quantified, dose-dependent)

Armour Thyroid

Most common
Headache (rate not quantified in labeling)
Tremors (rate not quantified in labeling)
Tachycardia/palpitations (rate not quantified in labeling)
Insomnia/nervousness (rate not quantified in labeling)

Levothyroxine vs. Armour Thyroid Dosage

Levothyroxine

Dosage
Dosage Table
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

Dosage
Dosage Table
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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