How Is Hashimoto's Disease Different From Hypothyroidism?

The thyroid gland is a butterfly-shaped gland weighing less than an ounce, located in front of the neck, just below Adam’s apple.

• The gland produces thyroid hormones called thyroxine (T4) and triiodothyronine (T3). These hormones regulate metabolism and influence various important parameters such as heart rate, body temperature, and digestion.
• Thyroid hormones play a crucial role in brain and sexual development.
• The release of thyroid hormones is regulated by another hormone called thyroid-stimulating hormone or TSH. It is produced by the pituitary gland that is located in your skull underneath the brain. The pituitary gland is further regulated by a part of the brain called the hypothalamus.

About 5 percent of the U.S. population is diagnosed with hypothyroidism, with many left undiagnosed due to subtle or no symptoms.

Depending upon whether the cause is in the pituitary, hypothalamus, or thyroid gland, hypothyroidism is broadly divided into two types:

1. Primary hypothyroidism: Occurs when the thyroid gland is producing lower amounts of thyroid hormones and may occur due to various reasons such as:
   • Hashimoto’s disease (most common)
   • Radioiodine therapy
   • Surgical removal of the thyroid gland
   • Radiation therapy
   • Dietary iodine deficiency
   • Congenital thyroid dysplasia
2. Secondary hypothyroidism: Occurs due to conditions affecting the hypothalamus or pituitary gland. Hypothyroidism due to conditions of the hypothalamus is also called tertiary hypothyroidism.

Hashimoto’s disease may not cause any symptoms initially. As the disease progresses, destruction of the thyroid gland results in symptoms of hypothyroidism such as:

• Poor tolerance to cold
• Weight gain
• Fatigue or lethargy
• Constipation
• Thinning of hair
• Dull, dry skin
• Menstrual irregularities
• Bodyache
• Joint pain
• Mood changes and depression

The inflammation of the thyroid gland may result in its enlargement called goiter, which is seen as a painless swelling in front of the neck that moves upon swallowing.

Goiter may cause issues such as:

• Difficulty swallowing
• Hoarseness of voice or difficulty speaking
• Trouble breathing
• Cosmetic concerns

With the continued autoimmune attack, the thyroid enlargement may go away and the gland may eventually shrink in size. In some people, excessive destruction of thyroid tissue may result in hyperthyroidism or increased thyroid hormone levels in the blood.

This rarely occurs and may cause symptoms such as:

• Palpitations
• Increased sweating
• Intolerance to heat
• Hand tremors
• Irritability
• Anxiety
• Difficulty sleeping
• Menstrual disturbances
• Reduced libido
• Unexplained weight loss

Hashimoto’s disease is diagnosed by a doctor based upon your detailed medical history, physical examination, and certain investigations (T3, T4, TSH levels, and TPO antibodies). 

Your doctor may ask whether other people in your family have any thyroid or autoimmune condition. They may also ask whether you are on any medications or have any history of thyroid medications, radiation exposure, or surgery in the head and neck region.

They may order blood tests to know the levels of thyroid hormones and certain antibodies raised in Hashimoto’s disease. Imaging studies such as ultrasound of the neck may be done to exclude other conditions that may cause your symptoms.

Hashimoto’s disease (also called chronic lymphocytic thyroiditis, Hashimoto’s thyroiditis, or autoimmune thyroiditis) results in the destruction of thyroid tissue by the immune system. 

• The immune system is normally designed to attack disease-causing agents such as bacteria, viruses, and fungi.
• In Hashimoto’s thyroiditis, the immune system attacks the thyroid tissue. This results in the accumulation of inflammatory cells that cause destruction and scarring in the thyroid gland.
• The damaged thyroid gland is not able to produce sufficient thyroid hormones resulting in hypothyroidism. 

The exact cause of Hashimoto’s disease is not known, but certain factors can increase your risk of Hashimoto’s disease, such as:

• Gender: Females are 4 to 10 times more likely to be affected than males.
• Genes: People with a family history of autoimmune or thyroid conditions have a higher risk.
• Age: Hashimoto’s disease is more likely to occur in the 30 to 50 years age group.
• Other autoimmune conditions: The presence of other autoimmune conditions, such as rheumatoid arthritis, Celiac disease, and type 1 diabetes, can increase the risk.
• Infections: Certain viral infections such as hepatitis may contribute to the causation of Hashimoto’s disease.

Treatment of Hashimoto’s disease mainly depends upon your symptoms and the levels of thyroid hormones in your blood.

• Asymptomatic patients are advised watchful waiting.
• If you have hypothyroidism, your doctor may prescribe synthetic thyroid hormone supplementation (levothyroxine). This medication is taken empty stomach in the morning, 30 to 60 minutes before having meals.
• If the goiter is causing significant discomfort, your doctor may suggest surgery.

Regular follow-up with your doctor is necessary to adjust the medication dosages and timely diagnose any complications that may occur. Follow-up visits will also help your doctor adjust your medications under special situations such as pregnancy.