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Does Armour Thyroid cause weight gain or weight loss?

Medically reviewed by Carmen Fookes, BPharm. Last updated on Sep 7, 2021.

Official answer


Although weight loss can be a side effect of Armour Thyroid in people taking it for low thyroid levels you should not take Armour Thyroid for the sole purpose of losing weight. Using Armour Thyroid to reduce weight in people with normal thyroid levels is dangerous, not safe, and can be life-threatening. Strokes, seizures, shock, coma, and death have been reported in people who have taken higher than recommended dosages of thyroid hormone preparations for weight loss. Some symptoms of Armour Thyroid toxicity (overdose), such as confusion, disorientation, sleep disturbances, or heart changes may not appear until several days after ingestion. Armour Thyroid should not be used as a treatment for weight loss or obesity. Weight gain is an uncommon side effect of Armour Thyroid but may occur if the dosage of Armour Thyroid is not supplementing your low thyroid levels enough.

It is not uncommon for people with low thyroid levels to lose up to 10% of their body weight when starting thyroid medications, such as Armour Thyroid. This weight is mainly water weight, since being hypothyroid makes you retain water and weight gain is one of the symptoms of hypothyroidism. Taking thyroid replacement therapy may reverse that weight gain. You may return to the normal body weight you would have been without the fluid retention caused by hypothyroidism. Once your thyroid levels are normal again, this medication should not affect your weight.

Armour Thyroid has a narrow therapeutic index – this means there is a fine line between taking too much or having too little. Over or under treatment can be detrimental to cardiovascular function, bone metabolism, reproductive health, emotional state, gastrointestinal function, glucose and lipid metabolism, and a young person’s growth and development.

Armour Thyroid preparations are a natural preparation, known as a desiccated thyroid extract, derived from porcine thyroid glands with a strong natural odor. Armour Thyroid is not proved by the FDA, has not been found to be safe and effective by the FDA, and the labeling is not approved by the FDA. Desiccated thyroid extracts are considered high risk for atrial fibrillation and other abnormal heart rhythms particularly in people over the age of 65. Another concern is that thyroid extracts have three and a half times more T3 than T4 compared to the ratio produced by a healthy human thyroid gland. If levels of T3 become too high this can affect heart health, bone density, and cause symptoms of an overactive thyroid. Most newer desiccated thyroid preparations contain standardized amounts of the thyroid hormones T3 and T4.

  • Harrar S. What You Need to Know About Hypothyroidism Extract Medications 23 March 2021.
  • Victor Bernet & Ana-Maria Chindris (2012) The potential dangers of supplements and herbal products marketed for improved thyroid function, Expert Review of Endocrinology & Metabolism, 7:3, 247-249, DOI: 10.1586/eem.12.16

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