ADHD or a Thyroid Problem?

The thyroid is a small gland in the neck whose hormones control how the body uses energy. When it makes too little or too much hormone, the effects can reach attention, memory, mood, sleep and energy. That is why a thyroid problem sometimes comes up when an adult is trying to understand new or worsening trouble with focus. This page compares ADHD with an underactive and an overactive thyroid, explains what the research does and does not support, and covers when a blood test makes sense.

Two thyroid problems, two different pictures

The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) describes them this way:

• Hypothyroidism (underactive thyroid). The thyroid does not make enough hormone and many body functions slow down. Nearly 5 out of 100 Americans aged 12 and older have it, although most cases are mild or have few obvious symptoms. It develops slowly, so symptoms may go unnoticed for months or even years.
• Hyperthyroidism (overactive thyroid). The thyroid makes more hormone than the body needs and many functions speed up. About 1 out of 100 Americans aged 12 and older have it.

Both are more common in women and in people over 60, according to NIDDK.

Side by side

The thyroid rows come from NIDDK, except the attention and memory row for hypothyroidism, which comes from a 2014 review in Current Opinion in Endocrinology, Diabetes and Obesity. The ADHD rows come from the National Institute of Mental Health (NIMH).

What the research supports

An underactive thyroid can affect thinking, and treatment helps

The 2014 review found that overt hypothyroidism is associated with problems in attention and concentration, memory, language and executive function, with memory the most consistently affected. These problems are largely reversible with thyroid hormone treatment, although perhaps not completely. Imaging studies show changes in brain regions involved in attention and working memory that improved after treatment in one report.

Milder, "subclinical" hypothyroidism is different. The same review found only small deficits in memory and executive function on sensitive tests, and no major neuropsychiatric effects. It concluded that people with mild hypothyroidism and significant distress from thinking or mood symptoms most likely have a separate condition that should be evaluated on its own. In other words, a slightly abnormal thyroid test does not usually explain significant, long-standing attention problems.

An overactive thyroid can feel like being wired

NIDDK lists nervousness, irritability, trouble sleeping, fatigue and shaky hands among the symptoms of hyperthyroidism. Those symptoms overlap with the restlessness of ADHD and with anxiety. A rapid or irregular heartbeat, heat intolerance and weight loss despite a good appetite are clues that point to the thyroid.

A specific inherited condition

One older finding is often repeated online. A 1993 study in the New England Journal of Medicine looked at 18 families with generalized resistance to thyroid hormone, an inherited condition caused by mutations in a thyroid receptor gene. Half of the affected adults (11 of 22) had met ADHD criteria as children, compared with 2 of 30 unaffected relatives. This is a specific genetic condition, not ordinary hypothyroidism or hyperthyroidism, and the study does not show that common thyroid problems cause ADHD.

Clues that point one way or the other

• Timeline. ADHD requires several symptoms before age 12. Focus or memory problems that are new in adulthood, especially with other body changes, make a medical cause more worth checking.
• Body symptoms. Unexplained weight change, feeling unusually cold or hot, hair or skin changes, a racing or slow heartbeat, or a swelling in the neck are not part of ADHD.
• Risk factors. NIDDK lists a family history of thyroid disease, a previous thyroid problem, pregnancy in the past six months and certain autoimmune conditions among the factors that make thyroid disease more likely.
• Mood. NIMH notes that thyroid disorders can cause the same symptoms as depression and that lab tests can help rule this out. See ADHD or depression?

Thyroid testing and the ADHD evaluation

NIMH says that during an adult ADHD evaluation a provider will ask about mood and current and past medical conditions to rule out other explanations. NICE, the UK's National Institute for Health and Care Excellence, likewise says an ADHD assessment should include physical health. Whether a thyroid blood test is needed is a clinical judgment based on symptoms, timing and history. If you have had thyroid tests, bring the results to the evaluation.

Thyroid status also matters if ADHD medication is considered. NIDDK lists a rapid or irregular heartbeat among the symptoms of hyperthyroidism, and the FDA label for Adderall XR warns that stimulants raise blood pressure and heart rate and that both should be monitored. A prescriber needs to know about any thyroid condition and its treatment.

Dr. Shershow's adult ADHD evaluation covers medical history, medications, sleep and substances, considers other explanations such as sleep problems, stress, anxiety and depression, and ends with what was found and the treatment options that fit. Sleep apnea is another medical lookalike worth knowing about; see ADHD or sleep apnea? For changes in focus that arrive around midlife hormone shifts, the guide on ADHD, perimenopause and menopause may also help.

What to bring to an evaluation

• Any thyroid blood test results from the past year, and the name of any thyroid medication you take.
• A note of when focus or memory problems began, and whether school reports mention them.
• Recent changes in weight, energy, heart rate, temperature tolerance or sleep.
• Family history of thyroid disease, ADHD, anxiety or depression.

The guide on preparing for an adult ADHD evaluation has a fuller checklist.

When to talk to a clinician

If you notice physical changes such as unexplained weight change, a racing heartbeat, feeling cold all the time or a swelling in your neck, see your primary care clinician; a blood test is how thyroid problems are confirmed. If trouble with attention and organization goes back to childhood and affects your work or home life, these are signs worth discussing with a clinician who evaluates adult ADHD. Both conversations can happen at the same time.

The adult ADHD self-test can help you describe your symptoms, but it cannot tell ADHD from a medical cause. To see how an evaluation works, read about adult ADHD testing in NYC or adult ADHD testing in New Jersey.