Hypothyroidism (Underactive Thyroid)

Diagnosis

Diagnosing hypothyroidism involves more than just evaluating symptoms, as they can vary from person to person and resemble other medical conditions. Therefore, healthcare providers rely primarily on blood tests to confirm the diagnosis.

The first test typically measures the level of thyroid-stimulating hormone (TSH) in the blood. A high TSH level suggests that the thyroid gland is underactive. To confirm, another blood test checks the level of the thyroid hormone T-4. If TSH is high and T-4 is low, it indicates hypothyroidism.

Sometimes, the thyroid hormone T-3 is also measured for a more detailed assessment. If TSH is elevated but T-4 and T-3 levels are normal, it may point to subclinical hypothyroidism — a mild form that often causes few or no symptoms.

TSH tests are also important for ongoing management, helping your healthcare provider monitor how well treatment is working and adjust medication doses as needed.

Certain medicines or supplements, such as biotin (often found in multivitamins), can affect test results. Always inform your healthcare provider about all supplements and medications you take before having blood tests.

Treatment

The main treatment for hypothyroidism is daily use of a thyroid hormone replacement medication, typically levothyroxine (Levo-T, Synthroid, and others). This medication restores normal hormone levels, helping to reverse symptoms like fatigue, weight gain, and dry skin.

Most people begin to feel better within one to two weeks after starting treatment, but the medication is usually needed for life. Since your hormone needs may change over time, your healthcare provider will check your TSH levels regularly — typically once a year — to ensure the dosage remains correct.

Finding the right dosage

Your healthcare provider will check your TSH levels about 6 to 8 weeks after starting levothyroxine to determine if your dose needs adjustment. Another test may follow after six months.

Too much levothyroxine can cause side effects such as:

• Fatigue

• Increased appetite

• Sleep disturbances

• Tremors or shakiness

• Heart palpitations

When taken in the correct dose, levothyroxine rarely causes side effects. If you switch medication brands, let your provider know, as the dosage may need recalibration.

For individuals with coronary artery disease or severe hypothyroidism, treatment usually begins with a low dose that is increased gradually to allow the heart to adapt safely to changes in metabolism.

Taking levothyroxine correctly

To ensure proper absorption, levothyroxine should be taken on an empty stomach at the same time each day. The ideal routine is to take it in the morning and wait 30 to 60 minutes before eating or taking other medicines. If taken at night, it should be at least four hours after your last meal.

Avoid skipping doses or stopping treatment, as symptoms will likely return. If you forget a dose, take two tablets the next day.

Some foods, supplements, and medicines can interfere with absorption, including:

• Iron supplements or multivitamins containing iron

• Calcium supplements

• Antacids containing aluminum hydroxide

• High-fiber diets or large amounts of soy products

Discuss your diet and medications with your healthcare provider to ensure the best results from your treatment.

Subclinical hypothyroidism

If diagnosed with subclinical hypothyroidism, treatment depends on your TSH levels and symptoms. For mild cases, medication may not be necessary. However, if TSH levels are higher or you experience related symptoms, your healthcare provider may recommend thyroid hormone therapy to help improve your overall well-being.