Hypothyroidism Symptoms: Underactive Thyroid Signs and Treatment

Hypothyroidism, also called underactive thyroid, occurs when your thyroid gland doesn't produce enough thyroid hormones to meet your body's needs. The thyroid is a small, butterfly-shaped gland located at the base of your neck that produces hormones regulating metabolism, energy production, body temperature, heart rate, and many other vital functions. When thyroid hormone levels are too low, your body's processes slow down, leading to a wide range of symptoms.

Hypothyroidism affects approximately 5% of Americans, with women being five to eight times more likely to develop the condition than men. The risk increases with age, particularly after age 60. The condition often develops gradually, and early symptoms can be subtle and easily mistaken for normal aging, stress, or other health issues. Many people don't realize they have hypothyroidism until symptoms become more pronounced or the condition is detected through routine blood work.

Common symptoms include persistent fatigue, unexplained weight gain, sensitivity to cold, dry skin, hair loss, constipation, muscle weakness, depression, and slowed thinking or memory problems. Because thyroid hormones affect virtually every organ system, hypothyroidism can cause diverse symptoms that vary from person to person. The good news is that hypothyroidism is easily diagnosed with a simple blood test and highly treatable with daily thyroid hormone replacement medication.

Common Causes

Hashimoto's Thyroiditis

Hashimoto's thyroiditis is the most common cause of hypothyroidism in the United States. This autoimmune disorder causes your immune system to attack and gradually destroy your thyroid gland, reducing its ability to produce hormones. The condition runs in families and is more common in women, particularly between ages 40-60.

Signs Hashimoto's might be the cause:

• You have other autoimmune conditions like type 1 diabetes or celiac disease
• Family members have thyroid problems or autoimmune diseases
• Blood tests show thyroid antibodies (anti-TPO or anti-thyroglobulin)
• You have a goiter (enlarged thyroid gland)

Thyroid Surgery or Radiation Treatment

Surgical removal of all or part of the thyroid gland (thyroidectomy) will cause hypothyroidism if the remaining tissue can't produce enough hormone. Similarly, radioactive iodine treatment for hyperthyroidism or radiation therapy for head and neck cancers can damage the thyroid gland and reduce hormone production.

Signs surgery or radiation might be the cause:

• You've had thyroid surgery or radioactive iodine treatment
• You've received radiation therapy to your head, neck, or chest
• Symptoms developed after these treatments
• You were previously diagnosed with hyperthyroidism

Medications

Certain medications can interfere with thyroid hormone production or function. Lithium (used for bipolar disorder), amiodarone (a heart medication), interferon alpha (used for hepatitis C), and some cancer immunotherapy drugs can cause hypothyroidism. High doses of iodine from supplements or medications can also affect thyroid function.

Signs medications might be contributing:

• Symptoms started after beginning a new medication
• You take lithium, amiodarone, or other medications known to affect the thyroid
• You use iodine-containing supplements or medications
• Blood tests showed normal thyroid function before starting the medication

Iodine Deficiency or Excess

Iodine is essential for thyroid hormone production. While iodine deficiency is rare in the United States due to iodized salt, it remains a common cause of hypothyroidism worldwide. Conversely, excessive iodine intake from supplements, certain medications, or seaweed consumption can also impair thyroid function.

Signs iodine imbalance might be involved:

• You avoid iodized salt or follow a very restricted diet
• You take kelp or seaweed supplements
• You live in an area with low soil iodine (historically the Midwest "goiter belt")
• You consume large amounts of certain foods that interfere with iodine absorption

Pituitary or Hypothalamus Disorders

Less commonly, hypothyroidism results from problems with the pituitary gland or hypothalamus rather than the thyroid itself. The pituitary produces thyroid-stimulating hormone (TSH), which signals the thyroid to produce hormones. If the pituitary or hypothalamus is damaged by tumors, surgery, or radiation, TSH production may decrease, leading to secondary hypothyroidism.

Signs a pituitary problem might be involved:

• You have symptoms of other pituitary hormone deficiencies
• You've had pituitary surgery or radiation
• Blood tests show low TSH along with low thyroid hormones (typical hypothyroidism shows high TSH)
• You have vision problems or persistent headaches

Congenital Hypothyroidism

Some babies are born with an absent, underdeveloped, or malfunctioning thyroid gland. Congenital hypothyroidism affects about 1 in 2,000-4,000 newborns. All newborns in the United States are screened for this condition because early treatment is critical for normal development.

Signs of congenital hypothyroidism in infants:

• Prolonged jaundice after birth
• Poor feeding or excessive sleepiness
• Constipation or infrequent bowel movements
• Detected through newborn screening tests

Pregnancy and Postpartum Thyroiditis

Some women develop thyroid inflammation during or after pregnancy (postpartum thyroiditis), which can cause temporary or permanent hypothyroidism. Pregnancy also increases thyroid hormone requirements, and women with subclinical hypothyroidism may develop symptoms during pregnancy.

Signs pregnancy-related thyroid issues might be involved:

• Symptoms developed during pregnancy or within a year after delivery
• You have a history of thyroid problems or thyroid antibodies
• You experienced extreme fatigue or depression after childbirth
• You have other autoimmune conditions

When to See a Doctor

You should consult a healthcare provider if you experience:

• Persistent fatigue that doesn't improve with rest
• Unexplained weight gain despite no changes in diet or activity
• Sensitivity to cold that's unusual for you
• Dry skin, brittle nails, or hair loss that's progressive
• Constipation that doesn't respond to dietary changes
• Muscle weakness, aches, or joint pain
• Depression, memory problems, or difficulty concentrating
• Irregular or heavy menstrual periods
• Slowed heart rate (below 60 beats per minute when not athletic)
• Hoarseness or changes in your voice
• Swelling in your neck (possible goiter)
• Family history of thyroid disease and you have symptoms

Seek immediate medical attention if you experience severe symptoms like extreme fatigue, confusion, decreased consciousness, or very low body temperature, as these could indicate myxedema coma, a rare but life-threatening complication of severe, untreated hypothyroidism.

Self-Care and Management Strategies

Take Medication as Prescribed

If diagnosed with hypothyroidism, take your thyroid hormone replacement medication (levothyroxine) exactly as prescribed, typically on an empty stomach 30-60 minutes before breakfast. Don't skip doses or stop taking medication without consulting your doctor, even if you feel better. Consistent medication is essential for maintaining proper hormone levels.

Monitor Your Symptoms

Keep track of your symptoms and energy levels, especially when starting treatment or adjusting medication doses. It can take several weeks to feel the full effects of thyroid medication. Report persistent or worsening symptoms to your doctor, as your dose may need adjustment.

Optimize Medication Absorption

Take thyroid medication on an empty stomach with water. Wait at least 4 hours after taking thyroid medication before consuming calcium supplements, iron supplements, antacids, or high-fiber foods, as these can interfere with absorption. Coffee may also affect absorption, so consider taking medication before your morning coffee.

Maintain a Balanced Diet

Eat a nutrient-rich diet with adequate protein, fruits, vegetables, and whole grains. Ensure sufficient selenium and zinc intake, which support thyroid function. Be cautious with soy products and cruciferous vegetables (broccoli, cauliflower, cabbage) in very large amounts, as they may interfere with thyroid function in some people.

Exercise Regularly

Regular physical activity can help combat fatigue, prevent weight gain, improve mood, and boost energy levels. Start slowly if you're experiencing significant fatigue, and gradually increase activity as your energy improves with treatment. Even gentle activities like walking or yoga can be beneficial.

Manage Stress

Chronic stress can worsen hypothyroid symptoms and may affect thyroid function. Practice stress-reduction techniques like meditation, deep breathing, yoga, or other relaxation methods. Prioritize adequate sleep (7-9 hours nightly) to support overall health and energy levels.

Get Regular Blood Tests

Have your thyroid hormone levels checked regularly as recommended by your doctor, typically every 6-12 months once your dose is stable, or more frequently when adjusting medication. These tests ensure your medication dose remains appropriate, as your needs may change over time.

Frequently Asked Questions

Prevention Tips

While you can't prevent most cases of hypothyroidism, particularly those caused by autoimmune disease or genetic factors, you can take steps to support thyroid health and catch problems early. Ensure adequate iodine intake through iodized salt and iodine-rich foods like fish, dairy, and eggs, but avoid excessive iodine from supplements unless recommended by your doctor. If you have a family history of thyroid disease or autoimmune conditions, ask your doctor about periodic thyroid screening, especially if you develop symptoms. Women planning pregnancy or who are pregnant should have thyroid function checked, as hypothyroidism can affect fertility and fetal development. If you're taking medications known to affect thyroid function (lithium, amiodarone, interferon), have your thyroid levels monitored regularly. Maintain a healthy lifestyle with balanced nutrition, regular exercise, adequate sleep, and stress management to support overall endocrine health. Avoid smoking, as it increases the risk of autoimmune thyroid disease. If you've had thyroid surgery or radioactive iodine treatment, follow up regularly with your doctor and report any symptoms promptly. Be aware of hypothyroidism symptoms, especially if you're at higher risk due to age (over 60), gender (female), family history, or other autoimmune conditions. Early detection and treatment can prevent complications and improve quality of life. If you notice symptoms like persistent fatigue, unexplained weight gain, cold sensitivity, or other signs of hypothyroidism, don't dismiss them as normal aging or stress—get your thyroid checked with a simple blood test.

The Bottom Line

Hypothyroidism is a common condition where the thyroid gland doesn't produce enough hormones to meet your body's needs, causing metabolism and other body processes to slow down. It affects about 5% of Americans, particularly women and older adults. The most common cause is Hashimoto's thyroiditis, an autoimmune condition, though thyroid surgery, radiation treatment, certain medications, and other factors can also cause it. Symptoms develop gradually and include fatigue, weight gain, cold sensitivity, dry skin, hair loss, constipation, muscle weakness, depression, and cognitive difficulties. Because symptoms can be subtle and nonspecific, many people don't realize they have hypothyroidism until it's detected through blood tests. Fortunately, hypothyroidism is easily diagnosed with a simple TSH blood test and highly treatable with daily thyroid hormone replacement medication (levothyroxine). With proper treatment, most people achieve normal thyroid hormone levels and complete resolution of symptoms. Treatment is typically lifelong, but medication is safe, effective, and inexpensive. If you're experiencing symptoms of hypothyroidism, especially if you have risk factors like family history or autoimmune disease, consult your healthcare provider for testing. Early diagnosis and treatment can prevent complications and significantly improve your quality of life.