- Hashimoto's Thyroiditis: This is the most common cause of hypothyroidism. It's an autoimmune disorder where the immune system mistakenly attacks and gradually destroys the thyroid gland.
- Thyroiditis: Inflammation of the thyroid gland can temporarily cause hypothyroidism. This includes subacute thyroiditis (often after a viral infection), postpartum thyroiditis (after childbirth), or silent thyroiditis.
- Treatment for Hyperthyroidism: Individuals who have been treated for an overactive thyroid (hyperthyroidism) with radioactive iodine therapy or surgical removal of the thyroid gland (thyroidectomy) often develop permanent hypothyroidism.
- Iodine Deficiency: Iodine is essential for thyroid hormone production. While less common in regions with iodized salt, a severe lack of dietary iodine can lead to hypothyroidism.
- Certain Medications: Some drugs can interfere with thyroid hormone production or function, including:
- Lithium (used for bipolar disorder)
- Amiodarone (a heart medication)
- Interferon alpha
- Some cancer medications
- Congenital Hypothyroidism: Some babies are born with an underdeveloped or absent thyroid gland.
- Pituitary Disorder: Rarely, a problem with the pituitary gland (which produces TSH, thyroid-stimulating hormone) can lead to the thyroid not being stimulated enough to produce hormones.
- Radiation Therapy: Radiation to the neck or head for other cancers can damage the thyroid gland.
- Fatigue and sluggishness: Feeling tired and lacking energy, even after adequate sleep.
- Weight gain: Despite no changes in diet or activity levels.
- Increased sensitivity to cold: Feeling cold even in warm environments.
- Constipation.
- Dry skin and brittle nails.
- Thinning hair or hair loss.
- Muscle aches, tenderness, and stiffness.
- Joint pain and swelling.
- Depression.
- Impaired memory and concentration ("brain fog").
- Slowed heart rate (bradycardia).
- Heavy or irregular menstrual periods in women.
- Hoarseness.
- Enlarged thyroid gland (goiter): A swelling at the base of the neck, though not always present.
- Medical History and Physical Exam: The doctor will ask about your symptoms, family history, and conduct a physical exam, checking your pulse, examining your neck for an enlarged thyroid, and looking for dry skin or other signs.
- Blood Tests:
- Thyroid-Stimulating Hormone (TSH): This is the most important test. In hypothyroidism, TSH levels are typically elevated (because the pituitary gland produces more TSH in an attempt to stimulate the underactive thyroid).
- Thyroxine (T4): Levels of this thyroid hormone will be low in hypothyroidism.
- Thyroid peroxidase (TPO) antibodies: These antibody tests can help diagnose Hashimoto's thyroiditis.
- Thyroid Ultrasound: May be used to visualize the thyroid gland and identify any nodules or structural abnormalities, though not typically for routine diagnosis of hypothyroidism.
- Thyroid Hormone Replacement Medication:
- Levothyroxine (Synthroid, Levoxyl, etc.): This synthetic form of thyroxine (T4) is the standard treatment. It is taken orally, usually once daily on an empty stomach.
- The dosage is carefully adjusted based on TSH levels to restore them to a normal range. It can take several weeks for symptoms to improve after starting medication or adjusting the dose.
- Regular Monitoring:
- Blood tests (TSH levels) are regularly performed to ensure the medication dosage is correct.
- Follow-up appointments with your doctor are essential to monitor symptoms and adjust treatment as needed.
- Dietary Considerations:
- Avoid taking levothyroxine with calcium, iron supplements, or certain foods (e.g., soy products, high-fiber foods) as they can interfere with absorption. It's best to take it at least 30-60 minutes before breakfast.
- While iodine deficiency is a cause, excessive iodine intake from supplements should be avoided, as it can sometimes worsen autoimmune thyroid conditions.