What is the most common cause of hypothyroidism in Australia?

From the Guidelines

The most common cause of hypothyroidism in Australia is Hashimoto's thyroiditis, an autoimmune condition where the body's immune system attacks the thyroid gland. This condition leads to chronic inflammation of the thyroid, gradually impairing its ability to produce sufficient thyroid hormones. Hashimoto's thyroiditis is particularly prevalent in women and tends to run in families, suggesting a genetic component.

Key Points

• The condition is characterized by chronic inflammation of the thyroid gland, leading to impaired production of thyroid hormones.
• Risk factors for an elevated TSH level include female sex, advancing age, white race, type 1 diabetes, Down syndrome, family history of thyroid disease, goiter, previous hyperthyroidism, and external-beam radiation in the head and neck area 1.
• Treatment typically involves daily oral levothyroxine, starting at doses of 50-100 mcg for adults, adjusted based on thyroid function tests every 6-8 weeks until optimal levels are achieved.
• Once stabilized, annual monitoring is usually sufficient, with the medication taken on an empty stomach, 30-60 minutes before breakfast, and separated from calcium, iron supplements, and certain foods that can interfere with absorption.
• Hypothyroidism requires lifelong treatment, as the condition typically progresses over time, with the thyroid gland becoming increasingly unable to produce adequate hormone levels.

Management

• The principal treatment for hypothyroidism is oral T4 monotherapy (levothyroxine sodium) 1.
• Although definitive data are lacking, treatment is generally recommended for patients with a TSH level that is undetectable or less than 0.1 mIU/L, particularly those with overt Graves disease or nodular thyroid disease.
• The serum TSH test is the primary screening test for thyroid dysfunction, with multiple tests done over a 3- to 6-month interval to confirm or rule out abnormal findings 1.

From the Research

Causes of Hypothyroidism in Australia

The most common cause of hypothyroidism in Australia is:

• Autoimmune chronic lymphocytic thyroiditis, characterized by raised circulating levels of thyroid peroxidase antibody 2 This condition is also known as Hashimoto's thyroiditis, which is a common cause of hypothyroidism worldwide 3

Prevalence of Thyroid Disease

Some key points about the prevalence of thyroid disease in Australia include:

• The prevalence of recognized thyroid disease is around 10% in the older Australian population 4
• An additional 3.6% of participants had unrecognized thyroid disease, with abnormal thyroid-stimulating hormone (TSH) levels 4
• The prevalence of hypothyroidism increases with age in women 4

Treatment and Management

Treatment for hypothyroidism typically involves:

• Replacement therapy with thyroxine, which is the cornerstone of therapy 2
• Levothyroxine monotherapy is the standard treatment for hypothyroidism, which is safe and inexpensive, and restores thyroid function tests to within the reference range 3