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Can Nature-Throid cause weight gain/loss?

Medically reviewed by Carmen Pope, BPharm. Last updated on Aug 31, 2023.

Official answer


Although weight loss can be a side effect of Nature-Throid in people taking it for low thyroid levels you should not take Nature-Throid for the sole purpose of losing weight. Using Nature-Throid 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 Nature-Throid toxicity (overdose), such as confusion, disorientation, sleep disturbances, or heart changes may not appear until several days after ingestion. Nature-Throid should not be used as a treatment for weight loss or obesity. Weight gain is an uncommon side effect of Nature-Throid but may occur if the dosage of Nature-Throid 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 Nature-Throid. This weight is mainly water weight, since being hypothyroid makes you retain water and weight gain is one of the symptoms of hypothyroidism. At most this usually leads to an excess of 10 to 20 pounds extra weight. 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. If you are still carrying excess weight it may be due to another type of hormone imbalance.

Nature-Throid 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.

Nature-Throid preparations are a natural preparation, known as a desiccated thyroid extract, derived from pig thyroid glands with a strong natural odor. Nature-Throid 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 desiccated thyroid preparations available today contain standardized amounts of the thyroid hormones T3 and T4.

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