Hashimoto's thyroiditis

Hashimoto's thyroiditis (also called autoimmune or chronic lymphocytic thyroiditis) is the most common cause of hypothyroidism in the UK. The immune system produces antibodies - most commonly TPO antibodies - that attack the thyroid over time, causing inflammation and gradual loss of function.

In the early stages, some people experience a brief phase of mild hyperthyroidism ('Hashitoxicosis') as damaged cells release stored hormone. Over months or years, the thyroid's ability to produce hormone typically declines and hypothyroidism develops.

Symptoms of the resulting hypothyroidism include fatigue, weight gain, feeling cold, constipation, slow heart rate, dry skin and hair, and low mood. Some people also have a mild goitre. Hashimoto's is much more common in women than men.

Hashimoto's is diagnosed through blood tests showing elevated TPO antibodies, often with a raised TSH as function declines. Treatment, when needed, is levothyroxine to replace the hormone the thyroid can no longer produce adequately. The autoimmune process itself is not currently treated with specific drugs in standard NHS practice.