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Why is Armour Thyroid not recommended?

Armour Thyroid is a desiccated thyroid extract derived from pig thyroid glands. It is not approved by the FDA and carries certain risks that lead many providers to avoid its use in favor of synthetic hormone replacements.

Inconsistent hormone content

  • Dosage variability from batch to batch
  • Frequent product recalls due to potency issues
  • Potential cross‑contamination with bovine tissues

Safety concerns in certain conditions

Providers may avoid Armour Thyroid for patients with:

  • Heart disease or arrhythmias
  • Hypertension or coronary artery disease
  • Adrenal insufficiency or thyrotoxicosis
  • Osteoporosis, liver or kidney disease

What does Armour Thyroid treat?

Armour Thyroid delivers both T3 (triiodothyronine) and T4 (thyroxine) hormones. It is used for:

  • Primary hypothyroidism
  • Hashimoto’s thyroiditis
  • Suppression of TSH in goiter or thyroid nodules

Side effects

  • Increased heart rate and palpitations
  • Chest pain
  • Tremor and muscle weakness
  • Sweating, anxiety, diarrhea
  • Rare allergic reactions or adrenal insufficiency

Drug interactions

Armour Thyroid may alter or be affected by:

  • Bile acid sequestrants (cholestyramine)
  • Insulin or oral diabetes agents
  • Estrogen‑containing contraceptives
  • Antacids with calcium or magnesium
  • Iron supplements
  • Warfarin
  • Midodrine

Use in pregnancy and breastfeeding

Levothyroxine is preferred during pregnancy for stable T4 levels. Armour Thyroid is rarely used, but any thyroid replacement should be managed by your provider to ensure fetal and infant safety.

Comparison with Synthroid (levothyroxine)

  • Armour Thyroid is natural extract containing T3 and T4
  • Synthroid is synthetic T4 only
  • Synthroid has more consistent dosing and lower cost
  • Armour Thyroid may cause more side effects and requires closer monitoring

Switching from Armour Thyroid to Synthroid

Transition should be supervised by a healthcare provider. Dosing and follow‑up thyroid function tests are needed to match hormone levels and avoid under- or over‑replacement.

Sources

  • Shah M et al. A comparison of Armour Thyroid and levothyroxine. J Endocr Soc. 2021.
  • Jonklaas J et al. Guidelines for treatment of hypothyroidism. Thyroid. 2014.
  • Armour Thyroid Package Insert. AbbVie, Inc. 2024.
  • National Institute of Diabetes and Digestive and Kidney Diseases. Hypothyroidism overview.
  • DailyMed. Levothyroxine sodium label.