Short answer: The Armour Thyroid label says side effects other than those of too much thyroid hormone (overdosage) are rare. Signs of too much include chest pain, a fast pulse, palpitations, excess sweating, heat intolerance and nervousness. It gives no percentages. The label has a boxed warning against use for obesity or weight loss, and it states the product has not been approved by FDA as a new drug.
What the Armour Thyroid label says it is for: Armour Thyroid is a dried thyroid extract from pig thyroid glands, giving 38 mcg of T4 and 9 mcg of T3 per grain. Its label lists use as replacement therapy for hypothyroidism of any cause except short-term hypothyroidism while recovering from subacute thyroiditis, and to suppress TSH in certain goiters, nodules, thyroiditis and thyroid cancer (Description; Indications and Usage). The label states it has not been approved by FDA as a new drug (How Supplied).
Source
ARMOUR THYROID (thyroid tablets, USP), prescribing information. AbbVie (Allergan). DailyMed, label revised March 2024. DailyMed setid 56b41079-60db-4256-9695-202b3a65d13d
Boxed warning: not for obesity or weight loss
Thyroid hormone drugs have been used to treat obesity. In people with normal thyroid function, usual doses do not cause weight loss, and larger doses may cause serious or even life-threatening toxicity, especially with stimulant appetite suppressants. The label calls this use unjustified and ineffective, and says thyroid hormone is also not justified for infertility unless hypothyroidism is present.
These are the label's own numbers from the Adverse Reactions section. Where the label compares with placebo (a dummy treatment), both columns are shown, so you can see how much more often a reaction happened on Armour Thyroid.
| Sign | Where the label lists it |
|---|---|
| Chest pain | Information for the Patient |
| Increased pulse rate | Information for the Patient |
| Palpitations | Information for the Patient |
| Excessive sweating | Information for the Patient |
| Heat intolerance | Information for the Patient |
| Nervousness | Information for the Patient |
| Angina (chest pain from the heart), a sign to lower the dose | Dosage and Administration |
The Adverse Reactions section says reactions other than those of overdosage are rare, and gives no percentages or placebo comparison.
Adverse reactions other than those of too much thyroid hormone, at the start or during maintenance, are rare.
Children may have partial hair loss in the first few months of therapy; the label says it is usually temporary.
In infants, excessive doses can cause craniosynostosis (early closure of the skull bones).
The active ingredient comes from pig thyroid glands, made in a facility that also handles cow tissue, so contamination with animal viruses or other agents cannot be ruled out. No cases of disease transmission have been reported.
The label says there is no well-documented evidence of true allergic or idiosyncratic reactions to thyroid hormone.
The Warnings and Precautions part of the label lists these. Each line gives the label's heading and what it means in plain words.
Who should not use it. Thyroid hormone is generally not used with uncorrected adrenal insufficiency, untreated thyrotoxicosis (overactive thyroid), or allergy to any ingredient.
Heart disease and older people. Thyroid hormone is used with great caution with heart or coronary artery disease, angina, or in older people. They start at low doses of 15 to 30 mg, and the dose is lowered if normal thyroid levels can only be reached by worsening heart disease.
Other hormone conditions. Thyroid hormone can worsen symptoms of diabetes, diabetes insipidus and adrenal insufficiency, so their treatments may need adjusting. Diabetes medicine needs may rise when thyroid replacement starts and fall if it stops.
Blood thinners. Thyroid status changes sensitivity to oral anticoagulants, so prothrombin time is monitored closely and the anticoagulant dose may need lowering.
Cholestyramine, colestipol and estrogen. Cholestyramine or colestipol binds thyroid hormone in the gut, so four to five hours are left between them. Estrogen or estrogen birth control may raise thyroid dose needs in people without a working thyroid gland.
Biotin and thyroid tests. Biotin can throw off thyroid blood tests; the label says to stop it at least 2 days before testing.
From the Information for the Patient (Precautions) that comes with Armour Thyroid:
Dose Track has a side-effect log. Each entry records the symptom, a severity (none, mild, moderate, severe or life-threatening), the date and an optional note, and can be tied to a specific dose or logged on its own. The history screen shows what you logged over time, which makes it easier to tell your prescriber when a reaction started and whether it is easing. The app records what you enter; it does not judge whether a symptom is serious. For anything on the label's call-your-doctor list, call your doctor.
This page is what the FDA label says, in plain words. It is not medical advice. Follow your prescriber, and ask them or your pharmacist about anything here.