As part of your body's endocrine system, the thyroid, a small butterfly-shaped gland in the front of the neck, helps to regulate metabolism. The thyroid produces hormones critical to the healthy functioning of the cardiac, respiratory and digestive systems, as well as growth and fertility. Thyroid disorders, such as Hashimoto’s disease and other forms of hypothyroidism, may have an effect on a person’s weight.
Thyroid and Weight
The thyroid secretes two hormones, triiodothyronine, or T3, and thyroxine, or T4. Because these hormones affect the body’s basic metabolic rate, or BMR, a disruption of thyroid function can affect a person’s energy, balance and weight. High thyroid levels and a high BMR can lead to weight loss, whereas low thyroid levels with a low BMR can cause weight gain.
An autoimmune disorder known as Hashimoto's disease, causes the body’s immune system to attack healthy thyroid cells, hampering the gland's production of hormones. Some individuals with Hashimoto's disease exhibit few or no symptoms, while others may complain of traditional hypothyroidism symptoms, including fatigue, constipation, cold intolerance and weight gain.
Hypothyroidism occurs when the thyroid does not produce a sufficient amount of thyroid hormone. Causes of hypothyroidism include Hashimoto’s disease, an inflammation of the thyroid, a congenital disorder, radiation treatment of the thyroid or surgical removal of the thyroid. An underactive thyroid can lead to weight gain as the result of accumulated salt and water. The amount of excess weight can vary, depending on the severity of the hypothyroidism. Underactive thyroid most likely bears no causal relationship to weight gain as the only presenting symptom.
Weight Loss and Thyroid Medication
Doctors treat Hashiimoto's disease and other forms of hypothyroidism by prescribing synthetic thyroid hormone. Treatment may lead to a small weight loss -- most likely less than 10 percent of body weight, according to the American Thyroid Association. A patient whose thyroid levels have returned to normal has the same ability to lose weight as a person without thyroid disease. Thyroid hormone used solely as a weight loss tool can have dangerous side effects, causing the loss of muscle protein along with body fat.