Hypothyroidism: Symptoms, Causes, and Treatment

Fatigue, weight gain, increased sensitivity to cold, dry skin, or feeling mentally and physically slower can occur for many reasons. However, one condition that should be considered is hypothyroidism, also known as an underactive thyroid.

Hypothyroidism occurs when the thyroid gland does not produce enough thyroid hormones to meet the body’s needs. Because thyroid hormones play an important role in regulating metabolism and the function of many organs, low thyroid hormone levels can cause several processes in the body to slow down.

Symptoms of hypothyroidism often develop gradually, and some people may have only mild or nonspecific symptoms. Therefore, hypothyroidism cannot be diagnosed based on symptoms alone. Blood tests play an important role in confirming the diagnosis.

What Is Hypothyroidism?

The thyroid gland is a small, butterfly-shaped gland located at the front of the neck. It produces thyroid hormones, which help regulate energy metabolism, body temperature, heart rate, and the function of the brain, muscles, and other organs.

Hypothyroidism is a condition in which the thyroid gland does not produce enough thyroid hormones to meet the body’s needs. As a result, some of the body’s normal processes may slow down.

Hypothyroidism can occur at any age, but it is more common in women and older adults.

Why Is Hypothyroidism Important?

With appropriate diagnosis and treatment, most people with hypothyroidism can maintain normal thyroid hormone levels and continue their daily activities as usual.

However, if left untreated, hypothyroidism can affect several aspects of health, including cholesterol levels, cardiovascular health, fertility, and pregnancy.

In very severe cases that remain untreated for a long period, a rare but life-threatening complication called myxedema coma may occur. This condition requires immediate treatment in a hospital.

Causes and Associated Factors

Hypothyroidism can have several causes, including:

• Hashimoto’s disease: An autoimmune condition in which the immune system attacks the thyroid gland, reducing its ability to produce thyroid hormones. It is a major cause of hypothyroidism.
• Thyroiditis: Inflammation of the thyroid gland can disrupt thyroid hormone production and release. Some people may eventually develop hypothyroidism.
• Thyroid surgery: Removing part or all of the thyroid gland can reduce the body’s ability to produce sufficient thyroid hormones. Complete removal of the thyroid requires thyroid hormone replacement.
• Radioactive iodine treatment: Radioactive iodine used to treat hyperthyroidism may reduce thyroid function and lead to hypothyroidism.
• Radiation therapy to the neck or upper chest: Radiation may damage thyroid tissue and affect its ability to produce hormones.
• Certain medications: Some medications can interfere with the production or function of thyroid hormones.
• Pituitary or hypothalamic disorders: Although less common, abnormalities in the pituitary gland or hypothalamus may disrupt the system that regulates thyroid hormone production.
• Too much or too little iodine: In some cases, inadequate or excessive iodine intake can affect thyroid function.

People with a family history of thyroid disease, autoimmune diseases, or previous thyroid-related treatments may have an increased risk of developing hypothyroidism.

Symptoms of Hypothyroidism

Symptoms can vary from person to person and often develop gradually. Common symptoms may include:

• Fatigue or low energy
• Increased sensitivity to cold
• Weight gain
• Constipation
• Dry skin
• Dry, thinning, or falling hair
• Muscle or joint pain
• Slower heart rate
• Difficulty concentrating or slower thinking
• Memory problems
• Depression or low mood
• Hoarse voice
• Heavy or irregular menstrual periods
• Fertility problems

However, many of these symptoms, such as fatigue, weight gain, and hair loss, can also occur with other health conditions. Therefore, symptoms alone cannot confirm a diagnosis of hypothyroidism.

When Should You See a Doctor?

You should consult a doctor if you have persistent symptoms that may be associated with hypothyroidism, particularly if several symptoms occur together, such as ongoing fatigue, increased sensitivity to cold, unexplained weight gain, constipation, or dry skin and hair.

People with a history of thyroid disease, thyroid surgery, radioactive iodine treatment, radiation therapy to the neck, or autoimmune diseases should discuss with their doctor whether thyroid function testing is appropriate.

People who have hypothyroidism and are pregnant or planning to become pregnant should inform their doctor because thyroid hormone levels and medication requirements may change during pregnancy.

Seek immediate medical attention if severe symptoms occur, such as significantly reduced consciousness, severe confusion, abnormally low body temperature, slow breathing, or rapid deterioration. Although rare, these symptoms may indicate a medical emergency.

How Is Hypothyroidism Diagnosed?

Doctors usually evaluate medical history, symptoms, physical examination findings, and laboratory test results. Important blood tests include:

• TSH (Thyroid-Stimulating Hormone): TSH is produced by the pituitary gland and stimulates the thyroid gland to produce thyroid hormones. In primary hypothyroidism, where the problem originates in the thyroid gland itself, TSH levels are typically elevated.
• Free T4: This test measures the amount of free thyroxine, one of the main thyroid hormones, in the blood. Evaluating TSH together with Free T4 helps doctors assess thyroid function more accurately.
• Thyroid Antibodies: In some cases, doctors may also test for thyroid antibodies to determine whether the condition is associated with an autoimmune disorder such as Hashimoto’s disease.

Laboratory results should be interpreted together with factors such as age, symptoms, underlying health conditions, pregnancy status, and other clinical information. Therefore, results should be evaluated by a healthcare professional.

Treatment

The main treatment for hypothyroidism is replacing the thyroid hormone that the body cannot produce in sufficient amounts. The medication most commonly used is levothyroxine, a synthetic form of the T4 thyroid hormone.

The appropriate dose varies from person to person and may depend on several factors, including age, body weight, the severity of hypothyroidism, underlying medical conditions, other medications, and pregnancy.

After starting treatment or adjusting the dose, doctors usually repeat thyroid blood tests to determine whether the dosage is appropriate. Once thyroid hormone levels are stable, periodic monitoring is generally recommended.

Patients should not stop taking levothyroxine or change the dose without medical advice. Taking too much or too little thyroid hormone can have negative effects on health.

How to Take Care of Yourself With Hypothyroidism

Along with medical treatment, several self-care measures can help support appropriate disease management:

• Take thyroid medication consistently as prescribed.
• Attend scheduled blood tests and follow-up appointments.
• Tell your doctor or pharmacist about all medications, vitamins, and supplements you take.
• Avoid taking iodine supplements or products marketed for thyroid health without professional advice.
• Eat a balanced and varied diet appropriate for your overall health.
• Exercise at a level appropriate for your health and physical condition.
• Inform your doctor promptly if you are pregnant or planning to become pregnant.

People with Hashimoto’s disease or autoimmune thyroid disease should be particularly cautious about taking high-dose iodine supplements or seaweed-based supplements without medical advice, as excessive iodine intake can affect thyroid function in some individuals.

Who Should Consult a Doctor or Healthcare Professional?

Medical evaluation should be considered if you:

• Have persistent symptoms that may suggest hypothyroidism
• Have a family history of thyroid disease
• Have undergone thyroid surgery or other thyroid treatments
• Have an autoimmune disease
• Are pregnant or planning to become pregnant
• Take medications that may affect thyroid function
• Are already receiving thyroid treatment but develop new or recurring symptoms
• Have abnormal TSH or T4 test results that have not yet been evaluated by a doctor

Summary

Hypothyroidism is a condition in which the body does not have enough thyroid hormones, causing several body processes to slow down. Symptoms may include fatigue, increased sensitivity to cold, weight gain, constipation, dry skin, and difficulty concentrating. However, these symptoms are not specific to hypothyroidism and may occur with other conditions.

Diagnosis therefore requires medical evaluation and blood tests, particularly TSH and Free T4. With appropriate treatment and regular monitoring of thyroid hormone levels, most people with hypothyroidism can successfully manage the condition and maintain their normal daily activities.

Prepared by: Pharm. Punyanooch Angkanawin

References

1. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Hypothyroidism (Underactive Thyroid)
2. American Thyroid Association. Hypothyroidism
3. NHS. Underactive thyroid (hypothyroidism)