Hypothyroidism, or an underactive thyroid, is a widespread health issue in Australia, affecting approximately 1 in 33 people. The thyroid gland plays a crucial role in regulating metabolism by producing hormones essential for the body’s energy use, growth, and development. When the thyroid fails to produce enough hormones, hypothyroidism develops, leading to symptoms like fatigue, weight gain, and cold intolerance.
The Leading Cause: Hashimoto’s Disease
The most common cause of hypothyroidism in Australia is Hashimoto’s disease, also known as Hashimoto’s thyroiditis. This is an autoimmune disorder where the body’s immune system mistakenly produces antibodies that attack the thyroid gland. Instead of defending the body against infections, these antibodies cause inflammation and damage to thyroid cells, impairing hormone production.
Hashimoto’s disease often leads to a gradual decline in thyroid function and may cause the gland to enlarge, forming a goitre. It is more prevalent in women and tends to occur more frequently as people age, particularly over 60 years.
Other Causes of Hypothyroidism in Australia
While Hashimoto’s disease is the primary cause, several other factors contribute to hypothyroidism, including:
- Thyroid Surgery: Removal of part or all of the thyroid gland due to nodules, cancer, or overactive thyroid can reduce hormone production.
- Radiation Therapy: Treatments targeting the head and neck, including radioactive iodine therapy for hyperthyroidism, may damage thyroid tissue.
- Medications: Certain drugs, such as lithium (used for bipolar disorder) and amiodarone (for heart rhythm issues), can interfere with thyroid function.
- Congenital Hypothyroidism: Some babies are born with an underdeveloped or malfunctioning thyroid gland; newborn screening in Australia helps early detection.
- Iodine Deficiency: Globally a leading cause, iodine deficiency is rare in Australia due to mandatory iodised salt in bread since 2009.
- Pituitary or Hypothalamic Disorders: Rarely, problems with these brain regions can lead to secondary hypothyroidism by disrupting thyroid hormone regulation.
Why Is Hashimoto’s Disease So Prevalent?
Australia is considered an iodine-sufficient country, which means iodine deficiency is uncommon. This shifts the main cause of hypothyroidism from nutritional deficiency to autoimmune origins. Hashimoto’s disease results from complex interactions of genetic predisposition and environmental triggers, causing the immune system to attack the thyroid.
Recognizing and Managing Hypothyroidism
Because hypothyroidism develops slowly, symptoms can be subtle at first. Common signs include tiredness, weight gain, dry skin, constipation, and feeling cold. Diagnosis is confirmed through blood tests measuring thyroid-stimulating hormone (TSH) and thyroid hormone levels.
Treatment primarily involves daily thyroid hormone replacement therapy (levothyroxine), which effectively restores hormone balance and relieves symptoms.
In Australia, Hashimoto’s disease is the main cause of hypothyroidism, accounting for the majority of cases due to its autoimmune nature. Other causes like surgery, radiation, medications, and rare congenital or pituitary disorders also contribute but are less common. Thanks to public health measures, iodine deficiency is no longer a significant factor.