Hypothyroidism risk factors: who is more likely to have an underactive thyroid

What hypothyroidism is

Hypothyroidism, also called underactive thyroid, is when the thyroid gland does not make enough thyroid hormones to meet your body's needs. The thyroid is a small, butterfly-shaped gland in the front of your neck. Its hormones control how your body uses energy, so without enough of them many of the body's functions slow down (NIDDK).

Nearly 5 out of 100 Americans ages 12 and older have hypothyroidism, although most cases are mild or have few obvious symptoms (NIDDK).

Who is more likely to have hypothyroidism

Women are much more likely than men to develop it, and it is more common in people older than 60 (NIDDK). You are also more likely to have hypothyroidism if you (NIDDK) (MedlinePlus):

• had a thyroid problem before, such as a goiter
• had surgery or radioactive iodine to correct a thyroid problem
• received radiation treatment to the thyroid, neck or chest
• have a family history of thyroid disease
• were pregnant or had a baby in the past 6 months
• have Turner syndrome, a genetic disorder that affects females

Your thyroid is also more likely to be underactive if you have other health problems, including (NIDDK):

• celiac disease
• Sjögren's syndrome, which causes dry eyes and mouth
• pernicious anemia, caused by a lack of vitamin B12
• type 1 or type 2 diabetes
• rheumatoid arthritis
• lupus

MedlinePlus lists type 1 diabetes in its version of this list (MedlinePlus). See also rheumatoid arthritis risk factors, anemia risk factors and type 2 diabetes risk factors.

What causes it

NIDDK lists these causes (NIDDK):

• Hashimoto's disease, the most common cause, in which the immune system attacks the thyroid
• thyroiditis, inflammation of the thyroid, including after giving birth (postpartum thyroiditis)
• congenital hypothyroidism, present at birth; most newborns in the United States are tested for it
• surgery to remove part or all of the thyroid; removing the whole thyroid always causes hypothyroidism
• radiation, including radioactive iodine for an overactive thyroid and radiation for head or neck cancers
• some medicines, including certain heart, bipolar disorder and cancer medicines

Less often, it is caused by too much or too little iodine in the diet, or by problems with the pituitary gland or hypothalamus. Iodine deficiency is extremely rare in the United States (NIDDK).

Hashimoto's disease risk factors

Hashimoto's disease is 4 to 10 times more common in women than men. It may occur in teens or young women, but more often develops in women ages 30 to 50. Your chance goes up if other family members have it (NIDDK). You are more likely to develop it if you have other autoimmune disorders, including celiac disease, lupus, rheumatoid arthritis, Sjögren's syndrome and type 1 diabetes (NIDDK).

Symptoms to mention to a doctor

Symptoms vary from person to person. Common ones include (NIDDK):

• fatigue
• weight gain
• trouble tolerating cold
• joint and muscle pain
• dry skin or dry, thinning hair
• heavy or irregular periods or fertility problems
• slowed heart rate
• depression

Because hypothyroidism develops slowly, you may not notice symptoms for months or even years. Many of these symptoms, especially fatigue and weight gain, are common and do not necessarily mean you have a thyroid problem (NIDDK).

Routine thyroid testing in adults without symptoms is a separate question; the thyroid function screening check covers what the USPSTF says about it.

Common questions

Is hypothyroidism a problem in pregnancy?

Left untreated, it can affect both mother and baby. Thyroid medicines can help prevent problems and are safe to take during pregnancy. Many women on thyroid hormone medicine need a higher dose in pregnancy, so NIDDK says to contact your doctor right away if you find out you are pregnant (NIDDK).

Does hypothyroidism affect cholesterol?

Yes. It can contribute to high cholesterol, and NIDDK says people with high cholesterol should get tested for hypothyroidism (NIDDK). See high cholesterol risk factors.

Which risk factors can I change?

Most cannot be changed: sex, age, family history, past thyroid treatment and other conditions (NIDDK). If you take one of the medicines that can affect the thyroid, ask your doctor before making any change.

Also see thyroid cancer risk factors and screening tests by age.