What is Armour Thyroid?

Armour Thyroid is a desiccated thyroid extract used to treat hypothyroidism (low thyroid hormone levels) and to suppress thyroid-stimulating hormone (TSH) in conditions like goiter or thyroid cancer. It is derived from porcine thyroid glands and contains both T3 (triiodothyronine) and T4 (thyroxine) hormones.

Armour Thyroid predates FDA regulation, so it remains available by prescription despite not having formal FDA approval. Variability between batches can lead to dose inconsistencies, and recalls have occurred when potency deviated from expected levels.

Unlike synthetic levothyroxine (Synthroid, Levoxyl, Tirosint, Unithroid) which provides only T4, or liothyronine (Cytomel) which provides only T3, Armour Thyroid delivers both hormones in combination.

Side effects

Side effects resemble hyperthyroidism symptoms:

  • Increased heart rate or palpitations
  • Chest pain
  • Tremors
  • Muscle weakness
  • Excessive sweating
  • Anxiety or nervousness
  • Diarrhea
  • Weight changes
  • Hair loss (often early in therapy)

Rare but serious reactions include:

  • Cardiac complications in those with heart disease
  • Adrenal insufficiency symptoms (fatigue, dizziness, abdominal pain)
  • Elevated blood sugar requiring diabetes medication adjustment
  • Severe allergic reactions (hives, throat swelling, difficulty breathing)

Drug interactions

Discuss all other medications, supplements, and vitamins with your provider. Notable interactions include:

  • Cholestyramine or colestipol (cholesterol‑lowering)
  • Other thyroid hormones (levothyroxine, liothyronine)
  • Diabetes drugs (insulin, metformin, glipizide, pioglitazone)
  • Combination birth control pills (norethindrone/ethinyl estradiol, ethinyl estradiol/norgestimate)
  • Iron supplements
  • Warfarin (blood thinner)
  • Midodrine (blood pressure medication)

Warnings and precautions

Before starting Armour Thyroid, inform your provider if you have:

  • Heart disease or arrhythmias
  • Adrenal gland disorders
  • Untreated thyrotoxicosis
  • Diabetes
  • Pregnancy or plans to become pregnant
  • Breastfeeding
  • History of allergic reaction to thyroid extracts

Administration timing

Take Armour Thyroid once daily, ideally 30–60 minutes before breakfast on an empty stomach. Swallow tablets whole or cut along the score line if needed. Maintain a consistent schedule and separate from interacting medications by at least four hours as directed by your healthcare provider.

Sources

  • NHS Guidelines for Hypothyroidism Treatment
  • Armour Thyroid Package Insert, AbbVie, Inc.
  • National Institute of Diabetes and Digestive and Kidney Diseases: Hypothyroidism Overview
  • Medscape: Thyroid Desiccated Extracts