The thyroid gland, located at the base of the neck below the Adam’s apple, is small in size but plays a critical role in many of the body’s systems. 

“Thyroid hormones help the body use energy, stay warm and keep the brain, heart, muscles and other organs working appropriately,” says Myrto Eliades, MD, an endocrinologist with INTEGRIS Endocrinology in Oklahoma City. “They do this by regulating the metabolism, which is the process by which our body uses energy. To analyze it more, thyroid hormones have the ability to stimulate the metabolic rate by increasing the number and size of mitochondria and other important enzymes and receptors that are involved in energy regulation inside our cells.”

Thus, problems arise when the thyroid doesn’t produce the right level of hormones. 

Hyperthyroidism, which is an overactive thyroid, is where patients show evidence of too much thyroid hormone,” says Mary Zoe Baker, MD, an endocrinologist with OU Health Harold Hamm Diabetes Center. She says symptoms include a “fast heart rate, unexplained weight loss, excessive sweating, hair change and loss, intolerance to the heat, anxiety and fatigue.”

In contrast, hypothyroidism is an under-active thyroid, in which there’s evidence of too little thyroid hormone. Symptoms include a slow heart rate, weight gain, cold intolerance, constipation, depression and fatigue. In addition, Baker says thyroid issues are more common in women, and most thyroid illnesses have an autoimmune cause.

Hashimoto Thyroiditis

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Eliades says the most common cause of hypothyroidism is Hashimoto’s thyroiditis, also known as chronic lymphocytic thyroiditis, an autoimmune disorder involving chronic inflammation of the thyroid, which may be hereditary. 

“Over time, the ability of the thyroid gland to produce thyroid hormones often becomes impaired and leads to a gradual decline in function and, eventually, an under-active thyroid (hypothyroidism),” she says. “Hashimoto’s thyroiditis occurs most commonly in middle aged women, but can be seen at any age, and can also affect men and children.”

Eliades says that while many people become concerned when they find that they have Hashimoto’s thyroiditis, not everyone with this condition requires medical treatment with thyroid hormone.

“Medical treatment is only indicated when the levels of the thyroid hormones are low,” she says. “Because the condition usually progresses very slowly over many years, people with Hashimoto’s thyroiditis may not have any symptoms early on, even when the characteristic thyroid peroxidase (TPO) antibodies are detected in blood tests.”

Grave’s Disease

The most common cause for hyperthyroidism, in more than 70% of cases, is Grave’s disease, says Eliades. 

“Grave’s disease is an autoimmune disease caused by antibodies that target the thyroid gland and cause it to grow and secrete too much thyroid hormone,” she says. “This type of hyperthyroidism tends to run in families, and it is seven to eight times more common in women than in men.” 

Thyroid Hormones for Weight Loss

Patients often ask Eliades if thyroid hormones can be prescribed as a treatment for weight loss in the absence of low thyroid hormones. Unfortunately, the answer is no.

“In the past, thyroid hormones had been used as a weight loss tool,” she says. “However, the effect is not significant and only transient. Once the excess thyroid hormone is stopped, any weight loss is usually regained. More importantly, studies have shown that the risks of such approaches outweigh the benefits. That is because excess thyroid hormone treatment includes the risk of major negative consequences, such as the loss of muscle protein, loss of bone, and/or heart problems such as arrhythmias. For these reasons, thyroid hormone treatment should not be used for weight loss.”