Lifestyle

An Overactive Thyroid Can Be Mistaken for Depression or Dementia in Older Adults. Signs to Know

By Erica Coleman · October 26, 2026

The thyroid is a small, butterfly-shaped gland in the front of the neck, and the hormones it makes help control how the body uses energy. When it makes more than the body needs, a condition called hyperthyroidism, many of the body’s functions speed up, according to the National Institute of Diabetes and Digestive and Kidney Diseases.

NIDDK says about 1 in 100 Americans ages 12 and older have hyperthyroidism, and that it is more common in women and in people older than 60. That second group is where it can be hardest to spot.

In older adults, NIDDK says, hyperthyroidism is sometimes mistaken for depression or dementia. MedlinePlus, from the National Library of Medicine, explains that adults over 60 may have different symptoms than younger adults. They may lose their appetite or withdraw from other people. NIDDK suggests asking a doctor about hyperthyroidism if you or a loved one shows these symptoms.

These are the signs listed by NIDDK, MedlinePlus and the American Thyroid Association. Not everyone has all of them.

Weight loss without trying. NIDDK lists weight loss despite an increased appetite. The American Thyroid Association describes it as weight loss despite a normal or even increased appetite.

A racing or irregular heartbeat. All three sources list a rapid or irregular heartbeat. The ATA describes it as feeling like the heart is racing or beating irregularly.

Shaky hands and weak muscles. NIDDK lists shaky hands and muscle weakness. MedlinePlus describes a tremor, usually in the hands.

Feeling too warm. NIDDK lists sweating or trouble tolerating heat, and the ATA mentions increased sweating and feeling hot.

Nervousness, irritability and poor sleep. These appear on all three lists. NIDDK and MedlinePlus also list fatigue, and MedlinePlus adds mood swings.

More frequent bowel movements. NIDDK and MedlinePlus both include this, and MedlinePlus and the ATA mention diarrhea.

A swollen neck. An enlarged thyroid, called a goiter, can make the neck look swollen. MedlinePlus says it can sometimes cause trouble breathing or swallowing.

The causes include Graves’ disease, which NIDDK calls the most common cause, along with thyroid nodules, inflammation of the thyroid and too much iodine. Overactive nodules are found most often in older adults, according to NIDDK. Some cough syrups and medicines, including some heart medicines, can contain a lot of iodine, as can seaweed and seaweed-based supplements.

There is another cause worth knowing for people who already take thyroid pills for an underactive thyroid. NIDDK says some people who take thyroid hormone medicine take too much. It advises seeing a doctor at least once a year to have hormone levels checked, and asking about interactions when starting new medicines.

Left untreated, hyperthyroidism can lead to serious problems, NIDDK says, including an irregular heartbeat that can lead to blood clots, stroke and heart failure, as well as thinning bones and osteoporosis.

Diagnosis can’t rest on symptoms alone, because many of them overlap with other diseases. NIDDK says doctors take a medical history, do a physical exam and use thyroid blood tests and imaging tests to confirm it and find the cause. Treatment is usually medicine, radioiodine therapy or surgery, and NIDDK says beta-blockers can ease symptoms such as tremors, rapid heartbeat and nervousness until other treatments start working.

This article is for general information and is not medical advice. Talk with your doctor about any symptoms and before changing any medicine, including thyroid medicine. This article was produced with the assistance of AI and fact-checked against the sources cited by LightWave Reports.